Chagas disease is turning up in (un)likely places. Who is ready for it?

Chagas

Photo by Clonny on Flickr. CC BY-NC-ND

Please welcome another guest post by Charles Ebikeme. –Beth

Chagas is a more dangerous and much more pervasive disease than we give it credit for. A tropical disease that is really no longer quarantined to the tropics, Chagas has been known to turn up in unlikely places — and those unlikely places are becoming more and more important.

Chagas is also known as American trypanosomiasis, and is found mainly in Latin America, where it is mostly transmitted to humans by the faeces of the triatomine “kissing bug”. About 7 to 8 million people are estimated to be infected with Chagas worldwide.

Recently, researchers at the Center for Clinical Epidemiology and Biostatistics demonstrated that bed bugs can transmit Trypanosoma cruzi, the infectious parasitic agent that causes Chagas disease. They found that bed bugs, a not too unrelated cousin of the kissing bug, can transmit the parasite in the same way by which humans are usually infected. Both bed and kissing bugs only feed on blood, and both hide in household cracks and crevices waiting for nightfall and the opportunity to feed on sleeping hosts.

The discovery that bed bugs can transmit Chagas is not the first time the disease has turned up via an unlikely route.

Distribution of Chagas' disease.svg

Traditional distribution of Chagas’ disease by Tomato356 at Wikipedia. CC BY-SA 3.0.

In March of 2001, a 37 year old woman went into surgery in the US to have a kidney and pancreas transplant from a donor that had already passed away. She would die six months later, on the first week of October from Chagas. The parasite had been contracted from the organ transplant.

Outside of the bite and faeces of the kissing bug the parasite can be transmitted in more (extra)ordinary ways — from mother to child, and through contaminated blood or organ donations. In the US blood supplies have only routinely been screened for Chagas since 2007.

In southern states of the US, the kissing bug also roams, and recent research has shown that some cases of Chagas disease are originating domestically. There’s a need to look more carefully for local infections in Texas and elsewhere in the South. And given the pathology of the disease, many people who are infected may not know they carry the parasite.

In recent years, it has become more apparent that Chagas is now not just confined to the Americas. It hasn’t been for some time. Chagas has now spread to other continents, and Europe is its most recent port of call.

The first reported case of Chagas in Europe was in 1981. Ever since then, sporadic cases have been detected in different European countries. Since the turn of the millennium the numbers of reported cases have only increased, particularly in Spain, Italy, and Switzerland. In Europe, the currently estimated number of people with Chagas is somewhere between 68,000 and 122,000, yet by 2009 only 4,290 had been diagnosed.

Chagas is a real threat. The global cost of the disease worldwide is thought to be at around 7.2 billion US dollars per year — an amount that is comparable to cervical cancer.

How prepared is Europe for Chagas?

Researchers, publishing in PLOS, sent out questionnaires on health policy for T. cruzi infection to about a dozen European countries. They wanted to gauge policy on the possibility of infection via blood transfusion, transplantation, and congenital transmissions. Some European countries are slowly beginning to acknowledge this growing public health problem, and some changes in health policies have been implemented.

Some, but not all, European countries have implemented national or regional measures to control transmission, but many countries still have no legislation about Chagas disease within their borders.

For risk of infection via blood transfusions seven European countries have either already implemented, or are in the process of, changing recommendations to enhance detection of cases of infection (France, Italy, Portugal, Spain, Sweden, Switzerland, and the United Kingdom).

No country in Europe has a specific health policy against the risk of infection by organ transplantation. Only in Italy, Spain, and the United Kingdom are donors at risk of the infection being screened.

Of all the three possible routes of extraordinary infection, it is the congenital route that is the least well developed in terms of health policy. This in the face of the fact that control of congenital transmission has been demonstrated to be one of the most cost-effective measures to control the disease, since newborns with acute disease can be cured easily if treatment and diagnosis is early.

The recommendation from authors is an evolving health policy to control Chagas disease transmission in Europe. Across Europe, the map of policies is a mixed one — some laws and directives concerning blood banks and transplant programmes are urgently needed to avoid and reduce the risk of transmission. The differences in regulations emanating from the European Commission are not always in line with the Council of Europe, which should be addressed to give some coherence. Where laws and regulations do exists, more effort needs to be made to evaluate their implementation and impact.

About Charles

charles_ebikeme (1)

Charles Ebikeme is a science journalist with a PhD in parisitology who serves as a Science Officer with the International Social Science Council of UNESCO and writes frequently on global health, health policy, neglected tropical diseases and infectious diseases for The Huffington Post, The Guardian, Scientific American, and Think Africa Press. He is based in Paris. You can find him on Twitter @CEbikeme.

 

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The flu shot isn’t a good match this year. Is it ever?

The CDC announced recently that this year’s flu vaccine is missing a key strain, one that accounts for 48% of what’s circulating. That strain, a “drifted” version of H3N2, was discovered in March 2014, but the vaccine strains for the Northern hemisphere, including the US, had been decided a month earlier. (The Southern hemisphere vaccine will include the drifted strain.)

Cue the overreactions: Natural News framed the advisory as an announcement that the vaccine “doesn’t work” (um, no) and a Fox News affiliate called the shot “useless” (likewise nope). The vaccine’s match is still better than 50%; if you believed the hype and skipped the shot, you’d be protected against, oh right, 0%.

“Doesn’t this happen every year?” was my friend’s reaction to the announcement that the vaccine wasn’t a good match. So I pulled up the CDC’s past reports to see how well the shot has been matching the circulating flu strains over the past few years. Take a look:

flu_match

How well the flu vaccine matched circulating strains over the past 5 years, including partial data from 2014. Click to embiggen; feel free to share with attribution. CC-BY.

Well, hey. That’s actually pretty good.

Where these numbers come from:

There are two series of tests the CDC does. The first, which you’ll find under Virologic Surveillance in each report, gives the percentage of each type of flu relative to the others (A/H3N2, B, A/H1N1, etc) in samples that turned up positive at hospital labs. Not everybody gets tested, but we can assume the strains that show up here correspond roughly to what’s circulating.

To find out whether the vaccine is a match, animals’ antibodies are given a chance to attack samples of circulating flu strains. This is listed under Antigenic Testing. In a good year, the antibodies all do their job, or they do it maybe 99.5% of the time and the last 0.5% is beyond the resolution of my colored pencils. The caveat here: only a small number of samples are tested in this way, so there is a risk of sampling bias, but once again it’s our best source of these numbers.

Most of the mismatches over the last few years came from B strain viruses. Flu vaccines often have just three strains: two A and one B. That’s called a trivalent vaccine. But if you get a chance to get the quadrivalent vaccine (which includes the nasal spray this year, and some but not all of the needle shots), you’re getting a second B strain. Last year, there were two types of B viruses that showed up in the test, and both were present in that year’s quadrivalent shot.

There’s another year on this chart with a big mismatch, and you may remember it: 2009, the grand entrance of a very special version of H1N1. That’s another case of a strain that popped up after the vaccine components had been decided, and so you might say that giant orange bar should be striped as a mismatch. But the threat from H1N1 was great enough that authorities commissioned a special second vaccine just to provide H1N1 coverage; I’ve written before about how I made sure to get that shot. I, and others who got both shots, were protected against nearly 100% of the circulating flu.

An important caveat: we’re just talking here about which strains match; the question of the shot’s overall efficacy is an issue for another time. The shot doesn’t provide complete protection, although in most years, for most populations, it’s somewhere around 60-70% effective for all the circulating strains combined. A meta-meta-analysis from 2012 summed it up like this:

Most influenza vaccines have been shown to confer some protection against naturally acquired infection and no evidence for major harms has emerged. In adults and children, the efficacy/effectiveness of current seasonal vaccines was generally high for laboratory-confirmed cases (especially for [the nasal spray] in children aged 2–17 y), and modest for clinically-confirmed cases and for the elderly.

 

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Maintaining health literacy through being web-savvy and culturally engaged

Note: The research discussed on the blog today is work from my PhD dissertation, which was published last week and covered by several media outlets online. It was originally blogged about on the Health Behaviour Research Centre ‘Health Chatter’ blog.

BritishMuseum

The British Museum in London.

Ageing involves many challenges for health and well-being. One under-recognised problem is that of declining literacy skills. While we are familiar with general issues of ageing such as loss of eyesight or physical mobility, what happens to literacy skills during ageing is much less well understood. Literacy is important to health during ageing because literacy is fundamental to managing health. For example, proper taking of medications, understanding what the doctor says, and understanding of written medical information all rely on having adequate literacy. When literacy is used in health contexts such as these, we refer to it as ‘health literacy’. The American Institute of Medicine defines health literacy as “the degree to which individuals have the capacity to obtain, process, and understand basic health information and services needed to make appropriate health decisions” (1).

The consequences of low health literacy include poor self-care of chronic disease, unnecessary use of emergency services, low use of preventive health services such as cancer screening, and increased risk of mortality (2–4). Health literacy declines during ageing. This is thought to be caused by the normal ageing-related decline in cognitive abilities such as mental processing speed and memory (5,8).

In our study, we were curious to see whether cognitively stimulating activities would help older adults to maintain their health literacy skills, regardless of any cognitive decline they experienced.

In particular, we examined whether internet use and engagement in several different types of social activities might help older adults to maintain health literacy. We used data from almost 4500 men and women aged 52 years and over in the English Longitudinal Study of Ageing (ELSA). The ELSA is a population-representative longitudinal study of English adults aged 50 and over, which aims to capture the experience of ageing in England. Since 2002, the study participants have been interviewed every two years about their health, economic, and social conditions. Data on health literacy were measured in 2004 and again in 2010 using a basic reading comprehension test of a medicine label.

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Health literacy was measured using a basic reading comprehension test of a medicine label

At the start of the study, we found that nearly one-third of adults had low health literacy, and that 18% of the study sample experienced a decline in their health literacy skills during the study follow-up period (9). People who were most at risk of declining health literacy were older, had no educational qualifications, had relatively low wealth, were ethnic minorities, and had difficulties with activities of daily living. On the positive side, consistent internet use over the six year study follow up period and engagement in cultural activities such as attending the opera, theatre, art galleries, museums, concerts, or the cinema appeared to protect against health literacy decline (9). The other types of social activities that we looked at were civic activities including being a member of a trade union, environmental group, neighbourhood group, and volunteering, and leisure activities including being a member of a sport or social club, or attending educational or musical classes. Alone, participating in civic or leisure activities had no effect on health literacy during ageing.

When we looked at the combined effects of engaging in none, one, two, three, or four of internet use and each of civic, leisure, and cultural activities, we saw an additive effect where the more activities adults engaged in, the more likely they were to maintain health literacy skills (9). People who engaged in all four of internet use, civic activities, leisure activities, and cultural activities over the study follow-up period had half the odds of losing health literacy skills as people engaged in none of these activities (Table). Importantly, all of these associations were independent of cognitive decline and other factors that might influence internet use and social activities such as wealth, social class, and health status.

Table. Additive effects of consistent engagement in any of internet use, civic activities, leisure activities, and cultural activities, the English Longitudinal Study of Ageing, 2004-11 (n=4368)

OR*

95% CI

Per additional activity

0.87

(0.81, 0.94)

Number of activities engaged in

 

 

     None

1.00

     One

0.93

(0.76, 1.14)

     Two

0.81

(0.63, 1.02)

     Three

0.70

(0.53, 0.94)

     Four

0.51

(0.33, 0.79)

*Adjusted for age, sex, ethnicity, educational attainment, net non-pension wealth, having a limiting long-standing illness, experiencing an IADL limitation, baseline executive function, baseline memory, executive function decline, and memory decline

Computer Keyboard

Internet use was associated with maintaining health literacy

What does this study mean? Well, first of all, that it is not inevitable that older people lose literacy skills as they age. It appears that internet use and social activities help with the maintenance of literacy skills. Even adults who experienced cognitive decline appeared to gain a benefit from using the internet and engaging in cultural activities. However, the main concerns are social inequalities in access to the internet and that cultural activities require time, money, and transportation. Older adults who are in poor health, have low wealth, and are from deprived backgrounds are the least likely to take advantage of the internet and to participate in cultural activities. They are also the most vulnerable to the loss of literacy skills as they age. Future research is needed to improve our understanding of how internet use and social engagement promote literacy skills, and to develop strategies to enable the most vulnerable individuals to benefit from technological advances and full participation in society.

This research was conducted at the Health Behaviour Research Centre at University College London, and funded by a Doctoral Foreign Study Award from the Canadian Institutes of Health Research, an Overseas Research Scholarship from UCL, and by programme grant funding from Cancer Research UK.

References

1.        Institute of Medicine. What is health literacy? In: Nielsen-Bohlman L, Panzer A, Hamlin B, Kindig D, editors. Health literacy: a prescription to end confusion. Washington D.C.: National Academies Press; 2004:31-58.

2.        Berkman ND, Sheridan SL, Donahue KE, Halpern DJ, Crotty K. Low health literacy and health outcomes: an updated systematic review. Ann Intern Med 2011;155:97–107.

3.        Kobayashi LC, Wardle J, von Wagner C. Limited health literacy is a barrier to colorectal cancer screening in England: Evidence from the English Longitudinal Study of Ageing. Prev Med 2014;61:100–5.

4.        Bostock S, Steptoe A. Association between low functional health literacy and mortality in older adults: longitudinal cohort study. BMJ 2012;344:e1602.

5.        Wolf MS, Curtis LM, Wilson EAH, Revelle W, Waite KR, Smith SG, et al. Literacy, cognitive function, and health: results of the LitCog study. J Gen Intern Med 2012;27(10):1300–7.

6.        Paasche-Orlow MK, Parker RM, Gazmararian JA, Nielsen-Bohlman LT, Rudd RR. The prevalence of limited health literacy. J Gen Intern Med 2005;20(2):175–84.

7.        Gazmararian JA, Baker DW, Williams M V, Parker RM, Scott TL, Green DC, et al. Health literacy among Medicare enrollees in a managed care organization. JAMA 1999;281(6):545–51.

8.        Federman AD, Sano M, Wolf MS, Siu AL, Halm EA. Health literacy and cognitive performance in older adults. J Am Geriatr Soc 2009;57(8):1475–80.

9.        Kobayashi LC, Wardle J, von Wagner C. Internet use, social engagement and health literacy decline during ageing in a longitudinal cohort of older English adults. J Epidemiol Community Health 2014;epub ahead of print. doi: 10.1136/jech-2014-204733

All images: Wikimedia Commons

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Interview with Joan Bloch: The connection between bus travel and preterm birth

bus_stop

Photo by Gray Monk, CC BY-ND 2.0

I spoke with Joan Bloch, PhD, CRNP, about her work on the causes of disparities in preterm birth. Although premature births are declining in America, African-American women are still far more likely than white women to have a baby born too early.

In a recent research project, presented at the American Public Health Association meeting, her team studied bus routes in the low-income areas of Philadelphia, PA where preterm birth is highest. They found that women likely spend upwards of 19 hours and $69 just for bus fare in the course of a healthy pregnancy—or, for a high risk pregnancy, 27 hours and $98.

On calculating bus travel for this project:

I have 30 years experience in caring for low income populations of women that take the bus to prenatal care, and I also work with people in my clinic and other clinics. So we had a panel of experts and a spatial analyst who rode around the city and we looked at different neighborhoods. We identified what would be a typical case, but maybe not such a dramatic case, right? Because we could go into a neighborhood where the houses are all boarded up and create a scenario where somebody has poor health behaviors and whatnot.

So we drove around and identified an apartment house, you know, young people often live in apartments. We identified an apartment house on a main street where there’s a bus stop right in front of it. And we said, [this hypothetical woman who lives here] gets pregnant, what would her travel through the bus system be like for prenatal care? And we just mapped it out.

On how to fix the situation:

I don’t know if we can make healthier places for everyone. That would be wonderful but that would take a long time. Maybe in 10 years we can make a bad neighborhood better, but in the meantime babies are being born every day, so what can we do to make it easier for those mothes to take care of their babies?

It would be great if we can have maternal/child centers, and mothers would come there, take care of their kids, and they can be cared for. [Agencies] could come together and make it one stop shopping. If the WIC program has their own building, maybe the prenatal care and infant care can be there too.

On why mothers travel just days after birth:

In efforts to decrease infant mortality, in this country we decreased the length of stay for mothers after childbirth in the hospital. Women who have a healthy normal delivery go home within 48 hours. But babies can go south quickly, so pediatricians, with good intentions, require that mothers bring their babies back to their pediatricians within two days after discharge.

So what that means is we’re sending mothers home right after this huge physological experience of childbirth and then they’re told they have to bring their baby back within 2 days. And the pediatricians in our city, at least at St. Christopher’s hospital, say that just about 100% of mothers do that.

I was talking to the medical students and they were saying “Ohh! Maybe that explains why we often see mothers with brand new babies on bus corners waiting for the bus. We thought they were totally negligent bringing out these newborn babies and taking them on the bus.”

And to think, what society has so little respect for the childbirth process we would expect a mother to leave her house just days after giving birth, and travel with her baby in tow? I think globally, from my experience and those of nurses around the world, we agree that mothers will do anything to make sure their babies are healthy. In most countries around the world they actually send nurses home to the mother’s house within that first week.

On changes in prenatal care over the years:

in the 1990s there were prenatal care adequacy indices that calculated the amount of prenatal care women got, to see if that was related to their outcomes, and that was actually based on 11 visits during the pregnancy. In our analysis, standards of practice have changed, increasing the number of visits. [Today, a woman] would have to make 25 different visits to get just regular prenatal care.

From 2000 to now, there’s been a plethora of health disparities research. But the reality is that even though we see so much in the literature, at the ground level, the teams I worked with 30, 20 years ago, we had much more resources.

We had a lot more time to spend with women. As a nurse practitioner, it’s not like I was scheduled like a mini doc every 15 minutes to see another patient. I could provide more well women’s health care.

In the past there was more ability to really work with a woman and her family and her support systems (or lack of support systems) and to run around in the neighborhood to get her what she needs. I think nowadays that has sort of been parceled out to funded safety net programs, so back then maybe we didn’t have them, but now there’s no real communication between all these different programs.

On how she got into her field:

I became a nurse in 1978, never knew a nurse in my life, but I was inspired, actually I was obsessed with racism as an adolescent. Like, why people could kill other people and harm other people just because they belong to a certain group. I had the opportunity to listen to Viktor Frankl and his words just resonated with me: Do something that’s going to be purposeful. Find meaning in your life, right? I looked through an occupational forecasting book and I saw nurses help people and I love math and science.

In nursing school when I saw birth it was like a miracle. Birth is a miracle. And I thought wow, I could help women and couples have healthiest birthing experience and babies.

When I went into the PhD program [after 20 years of nursing and teaching], I wanted to understand how the outcomes of health care services are evaluated, and particularly prenatal care. I grew up in nursing at a time there were a lot of changes. Childbirth classes, birthing rooms, I guess it was a product of the feminist women’s health movement. I wanted to know how this was evaluated on a public health level, and that led me into perinatal epidemiology.

On race and poverty:

I came into this work by just taking care of women & trying to promote each individual woman’s optimal health, and it wasn’t a race thing. In my dissertation work [on brain injury in newborns] I saw that if the mothers didn’t come to prenatal care, there was no relationship if the mother was white. But if the mother was black and she didn’t have prenatal care, those babies born to black mothers were two times more likely to have brain injury by 4 hours after birth.

But to tell you the truth once I did these maps, and saw the relationship with poverty and violence in the neighborhood & the racial segregation, it sort of shocked me, because it was so glaringly obvious, that it was more about living in bad neighborhoods. I think at the end of the day it really is about being poor. We need to take care of poor folks with a different approach than perhaps folks that have more resources. We need to take care of individual people and look at the context of their lives and help them be as healthy as they can be, and be sure they can take care of their children the best they can.

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Guest post: Economists should focus on the economy, not public health

Ed note: Please welcome Dr Travis Saunders back for another guest post. Travis Saunders has a PhD in Human Kinetics at the University of Ottawa. His research focuses on the health impact of physical activity and sedentary behaviour. He blogs regularly about both on his blog, Obesity Panacea.

We get it. Maclean’s Editor-at-Large Peter Shawn Taylor thinks that public health people (e.g. myself) should stay away from chronic disease (I guess it’s time to wrap up my research program and call it a career!). And he thinks that we should definitely stay away from any policies related to chronic disease that have anything to do with personal choice or the economy.

Earlier this month I sounded off on a recent Maclean’s editorial arguing that public health should prioritize infectious diseases like Ebola, rather than chronic diseases like cancer or obesity. This week, Mr Taylor repeated the same arguments in an opinion piece for the Globe and Mail concluding that:

It is not the job of public health to have an opinion on
taxes, economic policy, free trade or corporate control. Neither
should it be their business to interfere in the freely-made choices of adults.

Public health ought to stick to their needles, and leave the economy alone.

To recap: Mr Taylor (an economist and journalist) is well equipped to tell public health agencies how to run their business. Those of us trained in health research are not (one presumes it is because we are not economists). The level of condescension implicit in that line of reasoning is nothing short of astounding (if I ever meet Mr Taylor, I hope to ask him what he thinks of health economists… does their economic training qualify them to speak on important matters of public health, or are they disqualified by their training in public health?).

Unfortunately Mr Taylor does not present much in the way of arguments
to support his conclusions. He simply doesn’t believe that public health should include a focus on chronic diseases, because this might result in policies that impact the economy or personal choice. He does not claim that this would result in better policy, a healthier
society, or a stronger economy. The gist of his argument? We shouldn’t focus on chronic disease, because Mr Taylor doesn’t like it.

Here are some of Mr Taylor’s comments from the Globe and Mail, along with my responses (emphasis mine throughout):

The mission drift rampant in public health extends all the way up to the World Health Organization. At the peak of the
Ebola scare and with her organization under fire for mismanaging the on-the-ground response to the outbreak, last month executive director Margaret Chan was in Moscow attending a tobacco conference where she argued cigarettes are a bigger threat to global health than an African virus.
Last year she threw her lot in with the anti-corporate crowd, railing against “Big Food, Big Soda and Big Alcohol.”

As I noted last time around, this argument borders on willful ignorance for two reasons. First of all, Maclean’s (Mr Taylor’s magazine) has argued that the WHO failed to respond to Ebola not due to its focus on non-communicable diseases, but because it is chronically  nderfunded. Second, smoking is the # 1 preventable cause of death worldwide. At the risk of repeating myself, tobacco kills more people than Ebola every three days. So it absolutely makes sense to continue to focus on tobacco, even while we try to get a handle on the Ebola crisis.

The original − and very necessary − purpose of public
health was to combat infectious diseases and impose sanitary standards on water, food and waste. From this perspective, the field has enjoyed many successes, such as the eradication of polio and smallpox and the remarkable safety of Canada’s food system. Lately, however, public health departments seem to have lost sight of their primary mission. In a search for new things to control, or perhaps to pursue
personal ideological views, public health officials have pushed their way into areas they simply don’t belong.

As I noted in response to the Maclean’s editorial, this line of thinking is driven by ideology, rather than any clear logic. If you want to improve the health of a population, it makes no sense to draw an arbitrary line separating communicable and non-communicable diseases (keeping in mind that any line between the two is already blurring anyway).

By Mr Taylor’s logic, it would perfectly acceptable for public health campaigns to hand out condoms on university campuses, but not to warn people about the dangers of binge drinking, or drinking and driving (freely made choices of adults, etc). Take seat-belt laws – another unmitigated public health success story, despite infringing on our freedom to be thrown from a moving vehicle. A paper in the Review of Economics and Statistics concluded that “mandatory seat belt laws unambiguously reduce traffic fatalities”. And yet an exclusive focus on communicable diseases would have taken this option off the table
(unless, I assume, it was suggested by an economist).

Clearly Mr Taylor has an issue with public health agencies, in particular the public health unit in his hometown of Waterloo (although I know nothing of their policies, I can assure Mr Taylor that they did not invent the term “food swamp”). But I fail to see any convincing arguments (or any arguments at all really) in this new piece, or the earlier editorial from Maclean’s. There is no logical reason to allow public health to deal with infectious disease, but to bar it from dealing with other health-related issues. Arguing that you don’t like something isn’t really much of an argument.

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Red meat and cancer: the biological evidence

 

original

Is it all about cooking at high temperatures? | Gizmodo

Two weeks ago, we discussed the link between red meat consumption and breast cancer risk. This relationship is particularly interesting, given that younger women and those taking birth control pills were at the highest risk for breast cancer, indicating some kind of interaction between sex hormones and eating red meat. What wasn’t so well covered is the actual biological explanation for how red meat may contribute to causing cancer.

Current evidence is from large-scale population studies, which actually cannot tell us much about biological mechanisms. The first way these studies are done is through recruiting people who already have cancer, and matching them to similar people without cancer for comparison. Both groups – the cancer ‘cases’ and the healthy ‘controls’ – are asked about their historical consumption of red meat along other dietary and lifestyle factors that may also affect cancer risk. This is called a ‘case-control’ study. The second strategy involves recruiting a large group of healthy people, assessing their red meat consumption and other risk factors in real time, and following them forward in time to see who gets cancer and who doesn’t. This is called a ‘prospective cohort’ study, and provides more scientific validity than a case-control study because it happens in real time.

Both of these epidemiological strategies tell us a lot about population trends. Several, high-quality case-control and prospective cohort studies have consistently found relationships between red and processed meat intake and risks of breast cancer, colorectal cancer, death from cancer and cardiovascular disease, and overall risk of death. These relationships were independent of major dietary and lifestyle risk factors, which were carefully measured and statistically adjusted for (1-5).

There are hypotheses put forward by epidemiologists and biomedical scientists to explain the link between red meat intake and cancer risk:

1. Carcinogenic by-products of cooking meat at high temperatures

pah

Structural formulas of some PAHs | ATSDR

When meat is barbequed, grilled, or otherwise cooked at a high temperature, chemical by-products, which have the potential to cause cancer are formed. They are called heterocyclic amines (HCAs) and polycyclic aromatic hydrocarbons (PAHs). Both PAHs and HCAs have been found to be carcinogenic in rodents, but the biological evidence for humans is not yet well established (6).

HCA

The formation of HCAs during cooking |
Precision Nutrition

HCAs are formed when nutrients in meat – amino acids, sugars, and creatine – react together at high temperatures (6). PAHs are formed when fat and juices from meat drip onto an open flame, causing PAHs from the flame to stick to the surface of the meat (6). PAHs are also found in cigarette smoke and emissions from diesel fuelled-engines, so they are often studied in relation to air pollution (7). They have been linked to breast cancer in epidemiological studies, and this evidence is supported by biomedical research showing that PAHs are stored in the fat tissue of the breast, that they weakly mimic estrogen, and that they bind to DNA, forming damaging PAH-DNA adducts (7-9).

2. Nitrites and nitrates in processed meats

Nitrites and nitrates are found in processed meats, such as bacon, sausages, and hot dogs. In the large intestine, these compounds react with naturally occurring amines in meat to form carcinogenic N-nitroso compounds (NOCs). NOCs have been found to cause cancer in over 40 different animal species (10). Prospective studies have found a link between NOCs and gastrointestinal cancers, including oesophageal, stomach, and colorectal and rectal cancers (11-13). There is some evidence that the antioxidant vitamins C and E could help counteract the effects of NOCs (12,13), but further research is needed.

3. Hormone residues in meat

This explanation is one of the most worrying, as it would be due to growth hormones fed to cattle during farming. There is the least amount of evidence for this hypothesis, and surely there is strong political resistance from the meat industry against this possibility. In many places, use of growth hormones such recombinant bovine growth hormone (rBGH), which is actually more of a concern for dairy products, is banned or has been reduced in its usage. The Huffington Post has an interesting article on this issue.

4. Heme in red meat

The final hypothesis I will cover here is that of heme. Heme is the iron-containing chemical compound in red meat, also providing its pigment or colour. While dietary iron is crucial to good health, heme is also toxic in the digestive system. It has its own toxicity, but also acts to promote the formation of NOCs (14). Population-based cohort studies have found mixed evidence on the relationship between dietary consumption of heme from red meat and cancer incidence (15).

gut

The curiosity of the human gut microbiome | CR Way

Another current question is the role of genetics in how red meats are metabolised, and whether genetic differences may make some people more susceptible than others to any potential effects of eating red meat (16,17). An even newer and dynamic avenue of research is how the gut microbiome interacts with foods to produce health conditions (18). It also may be as simple as people who eat excessive amounts of red meat are probably not eating enough of other healthy foods that might help prevent cancer.

A lesson learned here is that science moves forward incrementally. Although the epidemiological evidence shows strong trends, not all of it is in perfect agreement. There is always some degree of human error present in the practice of research (19), which might obscure the truth. And, as we learn more, we also learn how much we don’t know. There are probably variations in metabolic genes and the gut microbiome within human populations that we don’t even know about yet, not to mention the biological and chemical factors in meat itself. Years from now, we may look back on today’s research as clunky and unrefined, unable to pick up more subtle aspects of the diet-cancer relationship.

In any case, the editors of the journal JAMA Internal Medicine have advocated that “Reducing meat consumption has multiple benefits for the world’s health” (20), a bold statement that future research will tell us more about.

 

References

1)Farvid MS, Cho E, Chen WY, Eliassen AH, Willett WC. Dietary protein sources in early adulthood and breast cancer incidence: prospective cohort study. BMJ 2014;348:g3437

2)Farvid MS, Cho E, Chen WY, Eliassen AH, Willett WC. Adolescent meat intake and breast cancer risk. Int J Cancer 2014; Published Online First 15 September 2014: doi: 10.1002/ijc.29218

3)Norat T, Bingham S, Ferrari P, Slimani N, Jenab M, Mazuir M, et al. Meat, fish, and colorectal cancer risk: the European Prospective Investigation into Cancer and Nutrition. J Natl Cancer Inst 2005;97(12):906-16.

4)Pan A, Sun Q, Bernstein AM, Schulze MB, Manson JE, Stampfer MJ, et al. Red meat consumption and mortality: results from 2 prospective cohort studies. JAMA Intern Med 2012;172(7):555-63.

5)Sinha R, Cross AJ, Graubard BI, Leitzmann MF, Schatzkin A. Meat intake and mortality: a prospective study of over half a million people. JAMA Intern Med 2009;169(6):562-71.

6)National Cancer Institute. Chemicals in meat cooked and high temperatures and cancer risk. http://www.cancer.gov/cancertopics/factsheet/Risk/cooked-meats (accessed 16 November 2014).

7)Breast Cancer Fund. Polycyclic aromatic hydrocarbons (PAHs).  http://www.breastcancerfund.org/clear-science/radiation-chemicals-and-breast-cancer/polycyclic-aromatic-hydrocarbons.html (accessed 17 November 2014).

8)Rundle A, Tang D, Hibshoosh H, Estabrook A, Schnabel F, Cao W, et al. The relationship between genetic damage from polycyclic aromatic hydrocarbons in breast tissue and breast cancer. Carcinogenesis 2000;21(7):1281-9.

9)Gammon MD, Santella RM, Neuget AI, Eng SM, Teitelbaum SL, Paykin A, et al. Environmental toxins and breast cancer on Long Island. I. Polycyclic aromatic hydrocarbon DNA adducts. Cancer Epidemiol Biomarkers Prev  2002;11:677-85.

10)Bogovski P, Bogovski S. Animal species in which N-nitroso compounds induce cancer. Int J Cancer 1981;27:471-4.

11)Jakszyn P, Gonzalez CA, Nitrosamine and related food intake and gastric and oesophageal cancer risk: a systematic review of the epidemiological evidence. World J Gastroenterol 2006;12(27):4296-303.

12)Zhu Y, Wang PP, Zhao J, Green R, Sun Z, Roebothan B, et al. Dietary N-nitroso compounds and risk of colorectal cancer: a case-control study in Newfoundland and Laborador and Ontario, Canada. Br J Nutr 2014;111(6):1109-17.

13)Loh YH, Jakszyn P, Luben RN, Mulligan AA, Mitrou PN, Khaw KT. N-nitroso compounds and cancer incidence: the European Prospective Investigation into Cancer and Nutrition (EPIC)-Norfolk study. Am J Clin Nutr 2011;93(5):1053-61.

14)Bastide NM, Pierre FH, Corpet DE. Heme iron from red meat and risk of colorectal cancer: a meta-analysis and a review of the mechanisms involved. Cancer Prev Res 2011;4(2):177-84.

15)Kim E, Coelho D, Blachier F. Review of the association between meat consumption and risk of colorectal cancer. Nutr Res 2013;33:983-94.

16)Ananthakrishnan AN, Du M, Berndt SI, Brenner H, Caan BJ, Casey G, et al. Red meat intake, NAT2, and risk of colorectal cancer: a pooled analysis of 11 studies. Cancer Epidemiol Biomarkers Prev 2014 (in press).

17)Ho V, Peacock S, Massey TE, Ashbury JE, Vanner SJ, King WD. Meat-derived carcinogens, genetic susceptibility, and colorectal adenoma risk. Genes Nutr 2014;9(6):430.

18)Feltman R. The gut’s microbiome changes rapidly with diet. Scientific American. 14 December 213. http://www.scientificamerican.com/article/the-guts-microbiome-changes-diet/ (accessed 17 November 2014).

19)Ioannidis JPA. Why most published research findings are false. PLOS Med 2005;2(8):e124.

20)Popkin BM. Reducing meat consumption has multiple benefits for the world’s health. JAMA Intern Med 2009;169(6):543-5.

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Category: Cancer, Epidemiology, Food industry, Health systems, Industry, Nutrition, Preventable Deaths | Tagged , , , , , , | 1 Comment

Does it even matter if gluten sensitivity is bogus?

Gluten Free "Wheat" Thins

Photo by Elana Amsterdam, who made these gluten free crackers. (CC BY-NC-ND 2.0)

This one goes out to all the Americans who are wondering if they really need to make gluten-free stuffing for Thanksgiving.

Gluten-free eating is popular; according to one industry trend study, a third of American adults are trying to avoid gluten, and most of those believe it’s healthy for people in general (rather than avoiding it for medical reasons). Lindsay Kobayashi wrote a great post here about why gluten-free is not the same as healthy, although the processed food industry doesn’t mind if you think it is.

With any trend, of course, comes a backlash. Last year, Australian researchers ran an experiment in which they gave gluten-free or glutenful muffins to people who said they feel like they are gluten intolerant. They had no terrible reaction to the gluten.

Cue the gleeful headlines about gluten sensitivity being “fake” or “bullshit.” (One reporter was researching an unrelated story about gluten free beer and was told by a somewhat confused press officer that, as a result of that study, “gluten free” no longer exists as a concept.)

I get it. You’re sick of hearing about gluten. Maybe you have a friend who shops the gluten-free aisles and you suspect she’s just making it up. Whoopie for you.

But does this line of research help your friend?

Who needs to know?

The situation reminds me of the Saturday Night Live skit about a “Home Headache Test.” In it, a woman complains of agonizing pain in her head, but is told “Honey, you don’t have a headache!”

Likewise, many people who are on a gluten-free diet have chosen it to try to deal with symptoms they are having. Whatever the cause, those symptoms are real. (Those who are trying gluten-free diets as a fad or a temporary challenge will eventually move on to the next fad. I wouldn’t worry about them.)

Scientifically there are two groups of people who believe they benefit from gluten free diets: those with celiac disease, in which an immune system reaction to gluten results in damage to the digestive tract, and those who have similar symptoms but test negative for celiac. In other words, they have “non celiac gluten sensitivity.”

One reason I can’t jump on the backlash bandwagon is because most people with celiac disease don’t know they have it. A study in 2012 that tried to determine the prevalence of celiac disease found it in 35 of the 7.798 people they tested. The kicker? 29 of them didn’t know until the study that they had it. If a fad encourages them to shun gluten, and it helps, that sounds like a win. The University of Chicago Celiac Disease Center estimates that 97% of people with celiac disease don’t know it.

With the average case of celiac taking 6 to 10 years to diagnose, it’s not surprising that people who discover a medical reason, and a simple diet-based solution, for their problems are ecstatic to celebrate that victory and share the news with others. Here is how the blogger and author known as Gluten Free Girl felt, after years of agonizing symptoms and inconclusive medical tests:

When I received the official diagnosis – you have celiac – I clapped my hands and said yes! The naturopath was a little surprised to see my celebration.

The gastroenterologist was even more surprised, the next week, when I showed up for my follow-up appointment in great health, blood test results in hand. He confirmed it – I have celiac. And he left the room, embarrassed.

I’ve written here before about how people embrace changes in diet because they are something you can take action about. Dropping gluten and curing your celiac disease definitely fits in that category. Few other conditions are that easy and dramatic; the only ones I can think of are food allergies and vitamin deficiencies, like when James Lind, in 1753, tested oranges as a scurvy cure.

A celiac diagosis is a get-out-of-jail-free card when it comes to the gluten backlash, but I want to go further.

Remember the Australian study that supposedly proved non-celiac gluten sensitivity to be fake? As some of the better reports explained, the study really did come with a helpful breakthrough for those patients: the symptoms they were chalking up to gluten may come from FODMAPs, a little-known group of carbohydrates that are found in many of the same foods as gluten. Before the study began, researchers put the 37 subjects on a low FODMAP diet, and found that patients’ symptoms improved right away, and weren’t affected by the introduction of low-FODMAP but gluten-laden muffins.

Peter Gibson, the senior author of that study, explained in an interview that a low-FODMAP diet is easier to follow and in his experience is a better initial recommendation: ”Our approach is to use a low FODMAP diet as our first dietary approach, and we would only restrict gluten in a very small proportion of patients where we’re not winning and we have a very strong belief that wheat is a cause of their symptoms.”

That’s a recommendation that can actually help patients, and is also something worth getting out the word about. FODMAPs are harder to keep track of than simply avoiding wheat or looking for a gluten-free label, but this may be a worthwhile diet. Here is a cheat sheet for foods to avoid and foods that are safe on a low FODMAP diet.

But 37 patients don’t completely answer the question; it’s a small study, and FODMAPs may not be the issue for everyone who seems to have trouble with wheat. For example, other wheat proteins (besides gluten) may also trigger symptoms. The scientific understanding of wheat/gluten intolerance is just beginning, not ending, and solutions will likely to turn out to be more complex than slapping gluten-free labels on products and selling them at a higher profit.

Bottom line: the science of nutrition exists to serve public health, which in turn exists to serve individuals’ health. If cutting out gluten seems to help, you don’t need a scientist’s permission to eat what you want while you wait for more research to roll in. And if that gluten-eschewing person is your friend? Just pass the wheat-free stuffing already.

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Why does eating red meat elevate breast cancer risk, especially for young women on the pill?

 

redmeat

How does a delicious juicy steak increase breast cancer risk? | Image: Lou Ferrigno

The answer to that question is unknown, although it may have its origins in the underbelly of the American food system. Let us unravel how red meat consumption may be associated with breast cancer risk. The U.S. Nurses’ Health Study II provides some striking evidence: compared with women who ate one serving of red meat per week, women who ate 1.5 servings of red meat per day had a 22% increased risk of breast cancer (2).

What was done: the U.S. Nurses’ Health Study II

This was a longitudinal cohort study of 116,430 female registered nurses who were 24 to 43 years of age when the study began. In 1991, the nurses filled out a validated food frequency questionnaire, which asked about their usual dietary intake and alcohol consumption in the past year. “Red meat” items were defined as:

  • Beef
  • Pork
  • Lamb
  • Hamburger
  • Hot dogs
  • Bacon
  • Sausage
  • Salami, bologna, and similar deli meats

The nurses were followed-up until 1 June 11, or date of breast cancer diagnosis or death, if either of those came first.

What was found: the association between red meat consumption and breast cancer risk

Among all women, those who ate red meat 1.5 times per day had a 22% increased risk of breast cancer, compared with those who ate red meat once per week.

The risk of breast cancer increased by 13% per additional daily serving of red meat.

This association was independent of other important breast cancer risk factors, such as age, smoking status, oral contraceptive use, childbirth factors, body mass index, alcohol intake, and caloric intake.

The really concerning finding comes here:

The risk of breast cancer increased by 54% per additional daily red meat serving among current oral contraceptive users.

This figure is a substantial increase to the above-cited 13% risk increase for users and non-users combined.

On a positive note, the authors observed that poultry consumption before menopause reduced post-menopausal breast cancer risk. Each additional daily serving of poultry was associated with a 25% lower risk of post-menopausal breast cancer. They also observed that substituting servings of red meat with servings of poultry, legumes, nuts, and fish was associated with reduced breast cancer risk.

What else do we know?

The authors conducted follow-up research after this study was published. Using the same dataset, they hypothesized that eating red meat earlier in life would be particularly bad in terms of breast cancer risk (2, 3). In an interview with the Harvard School of Public Health, Maryam Farvid, the lead investigator, said:

We developed this hypothesis based on the results from atomic bombings of Hiroshima and Nagasaki. Girls and young women who were exposed to this radiation had a higher risk of breast cancer later. But women who were exposed at age 40 or older did not have an increased risk.

True to form, consumption of red meat during adolescence was associated with a higher risk of pre-menopausal breast cancer (developing earlier in life), but not post-menopausal cancer (developing later in life) (3). Mammary glands appear to be more susceptible to carcinogenic factors during development and growth; red meat consumption appears to be no exception.

Why is red meat a potential cause of breast cancer?

The authors provide two mechanistic hypotheses. The first is through the carcinogenic by-products of cooking meat at high temperatures (i.e. grilling or barbequing). The second mechanism that the authors propose is through ‘hormone residues of the exogenous hormones for growth stimulation in beef cattle’ (1).

This latter hypothesis – hormone residues in beef cattle – is intriguing and alarming. Unfortunately, the authors do not expand on the policy implications. The topic is certainly political and has huge implications for all women (and men) consuming red meat in the United States. Studies from international contexts with different cattle industry regulations would be useful for comparison with this study in the American context.

The risk associated with eating red meat appeared to be the highest among women who took oral contraceptive pills. Adolescence appeared to be a critical time period in life where the effects of eating red meat were the strongest. How do we explain these results, given that several breast cancer risk factors are hormonal in nature, or thought to act through hormonal pathways? Whether hormone residues or some other factor related to the meat is the culprit, some kind of biological interaction appears to be occurring between red meat and sex hormones.

Given the ubiquitous consumption of red meat and oral contraceptive pills, these issues demand attention.

References

1)   Farvid MS, Cho E, Chen WY, Eliassen AH, Willett WC. Dietary protein sources in early adulthood and breast cancer incidence: prospective cohort study. BMJ 2014;348:g3437

2)   Harvard School of Public Health. News: Red meat consumption and breast cancer risk. http://www.hsph.harvard.edu/news/features/red-meat-consumption-and-breast-cancer-risk/ (accessed 5 November 2014).

3)   Farvid MS, Cho E, Chen WY, Eliassen AH, Willett WC. Adolescent meat intake and breast cancer risk. Int J Cancer 2014; Published Online First 15 September 2014: doi: 10.1002/ijc.29218

Category: Cancer, Epidemiology, Food industry, Industry, Infectious disease, Nutrition | Tagged , , , , , | 2 Comments

Guest Post: Public health agencies should prioritize public health based on evidence, not fear

The Editorial: The complexity of health requires an expansion of the areas covered by public health agencies

Ed note: This post comes to us from our PLOS Blogs friend Dr Travis Saunders. Travis Saunders has a PhD in Human Kinetics at the University of Ottawa. His research focuses on the health impact of physical activity and sedentary behaviour. He blogs regularly about both on his blog, Obesity Panacea.

I came across an editorial in Maclean’s this weekend which was both surprising and disappointing (and at times condescending). The gist of the editorial was that public health agencies like the World Health Organization (WHO), Centers for Disease Control and Prevention, and Public Health Agency of Canada, should focus on infectious diseases (Ebola, smallpox, SARS, etc), rather than chronic diseases (heart disease, diabetes, cancer, etc).

I like Maclean’s, and read it regularly. In fact, I was disappointed specifically because their science and medical coverage is so consistently excellent. The now-retired Science-Ish column, written by current Vox contributor and Knight Science Journalism Fellow Julia Belluz, was a fantastic model of high profile science/medical communication. Health feature writer Kate Lunau is also great. Everything I know about Polish democracy, I owe to Maclean’s political writer Paul Wells. So while Maclean’s is typically a great, evidence-based read, this editorial was neither.

Let me begin by saying that I’ve been appalled at how slow the response to the Ebola epidemic has been. Before I get to the editorial, I would like to urge everyone to consider donating to Medecins sans Frontieres, who are coordinating much of the Ebola response. There’s no question this is an important health issue that demands attention. However, I fail to see how prioritizing focus on infectious diseases over the long term at the expense of chronic disease will improve health (especially in developed nations).

Ok, now to my complaints. Below are my arguments, along with excerpts from the editorial (emphasis mine throughout).

Ebola vs cigarettes

From the editorial:

More than 4,500 Africans have died of Ebola to date. The number of new infections is doubling every month. Health facilities in hot-zone countries Guinea, Liberia and Sierra Leone are overwhelmed and understaffed. And while Canada has so far been lucky in avoiding infection, on Sunday, U.S. President Barack Obama mustered the Pentagon into the fight after the botched response by civilian authorities left the American public nervous. Meanwhile, the head of the World Health Organization (WHO)—the UN body meant to provide leadership during international health emergencies—has bigger things on her mind.

Last week, as the Ebola crisis deepened, the director-general of the WHO, Margaret Chan, was in Moscow hosting a conference on tobacco control. “Yes, Ebola is truly an issue of international concern,” she told the Wall Street Journal. “But tobacco—if we put the evidence on the table—tobacco control is still the most cost-effective and efficient way of reducing unnecessary diseases and deaths arising from using such harmful products.” The conference concluded with an agreement on the necessity for ever-higher tobacco taxes. (Canada and the U.S. boycotted the assembly because of sanctions against Russia.)

Ebola may be scary, but cigarettes are scarier.

While diseases like Ebola are terrifying, the death tolls are still relatively small compared to chronic diseases, even in many developing countries. Smoking is the # 1 preventable cause of death worldwide, and is responsible for roughly 17% of deaths in Canada. So quite frankly, it does make sense for the WHO and other public health agencies to discuss ways to reduce tobacco related deaths, even while the Ebola response is ongoing.

Let’s put this in perspective. So far, 4,922 people have died worldwide from Ebola. In Canada alone, 37,000 died in 2011 due to tobacco use. An astounding 480,000 Americans died in 2010 from tobacco related deaths. Put another way: tobacco kills more people than Ebola every three days. So yes, cigarettes are scarier than Ebola, at least in terms of their ability to kill.

And that’s just cigarettes. As chronic diseases account for an ever greater percentage of deaths worldwide (68% of all deaths worldwide are due to chronic disease in 2012), it seems reasonable that public health agencies give them increased attention. By any objective measure, reductions in smoking rates, and related reduction in tobacco-related deaths are an unmitigated public health success story.

Change of focus, or lack of funding?

As Maclean’s illustrated in their cover story last week, the WHO’s inability to deal with the Ebola outbreak isn’t due so much to their focus on chronic diseases like obesity, as to the fact that their funding has been diminishing for years. From that cover story:

The WHO has failed to provide that leadership, [Kelley Lee, a global health professor at Simon Fraser University] explains, for a “perfect storm” of reasons: an ineffective WHO African regional office, political and economic instability in the area and, most of all, because it doesn’t have the money it needs to do its job. The WHO’s regular budget has promised “zero real growth” since the 1980s, only increasing spending to account for inflation. It tightened its belt further in the late ’90s and froze the budget in absolute terms.

In contrast to their article above, the editorial implied that the reason for the spread of Ebola was because of “mission drift” towards a focus on chronic diseases. From the recent editorial:

Unfortunately, this sort of bizarre mission drift is not unique to the WHO. Public health officials around the world have succumbed to a similar preference for tackling issues of personal choice, the free market and political causes apparently inspired by the Occupy movement. The predominant public health fixation in developed countries these days is the so-called obesity epidemic and the alleged need for food taxes, along with other intrusive measures, such as New York’s failed Big Gulp soda ban, to correct this situation.

The mandate of any public health organization is to promote health. Period.

If your goal is to promote health/reduce the risk of disease, then it makes sense to focus on whatever factors are linked to disease… be they viruses, behaviours, or income. At some times and locations it will make sense to focus on infectious diseases, at others on chronic diseases. As discussed below, there are some countries that need to focus on both simultaneously.

The only real argument against focusing on all disease, and all causes of disease, is that some people object ideological grounds, in the absence of data. But there isn’t a strong case to be made in terms of evidence. The Social Determinants of Health framework has shown that the environment you are exposed to have direct impacts on your health – the neighbourhood you live in, the people you associate with, your family structure, all of these can impact health in a multitude of ways. Health is not exclusively at the mercy of bacteria or viruses. This was nicely illustrated in an article published in Macleans in 2013, which included this extremely informative infographic:

Image via Macleans.ca

And now the most confusing portion of the editorial

Last year, Toronto’s activist public health office chastised ABC TV for adding actress Jenny McCarthy, a vaccination critic, to the cast of its talk show The View. It is apparently necessary to remind public health officials that their mandate (and competency) does not include individual food choices, income disparity, trade, agricultural policy or network programming decisions.

This year has shown a tremendous spike in the number of measles cases in the US (see image below). Most of the infected individuals were unvaccinated. Thus, the reason that public health agencies objected to Jenny McCarthy getting a daily television platform is that she is the standard bearer of the anti-vaccine movement. Even if public health agencies focused primarily on infectious diseases as the editorial suggests, it would still make sense for them to publicly oppose her views, and to advocate against giving her a prominent daily platform on network TV. While we cannot stop the network from hiring her, we can be outspoken critics of the dangerous views she represents, and ensure that the public understands that her views do not represent the mainstream, and in fact represent a dangerous alternate reality.

Chronic diseases are a considerable (and increasing) burden, even in developing nations.

While the leading causes of death and disease in Africa are mostly infectious in origin, their role has been decreasing, while the role of chronic diseases has been increasing. Between 1990 and 2010, the disease burden of diabetes in sub-Saharan Africa increased by almost 90%. Only HIV/AIDS saw a greater increase in disease burden than diabetes over this period. The burden due to stroke and heart disease also saw increases of more than 30% during that period, while the disease burden due to respiratory infections, diarrheal diseases and malnutrition all decreased by 15-35%. This is not to say that infectious diseases have been vanquished – HIV and malaria remain the top causes of death and disease in Sub Saharan Africa – but developing nations have the unenviable task of addressing high rates of infectious disease while also seeing increasing levels of chronic disease; a situation referred to as the “double burden” of disease.

The line between infectious and chronic diseases is blurring.

We’re now finding out that several types of cancer (cervical, throat, etc) are linked to viruses, and are therefore in some sense an infectious disease (so too is obesity, and other disease-virus links are likely to follow). At the same time, advances in medications have led some to suggest that HIV is essentially a chronic disease, since it can be managed more or less indefinitely with proper medications (a key characteristic of chronic diseases is that they are long lasting, typically with no true “cure”). If public health agencies were to focus primarily on infectious diseases, would cancer be included? Only those that are specifically linked to viruses? What about HIV? Would that be too much “mission drift”? Or should we only focus on diseases that are dominating the news cycle at any particular point in time?

Final thoughts

Image source

Chronic diseases are much more complicated than infectious ones. We know what causes Ebola, smallpox, and HIV. While it’s not necessarily easy to prevent or cure these diseases, at least the process is itself relatively simple. Contrast that with the risk factors for obesity in the above graphic (a similar graphic could be made for heart disease or diabetes). With a chronic disease it’s often difficult to even determine the key risk factors, let alone agree on the best methods of treatment or prevention.

I know that many people are ideologically opposed to public health agencies focusing on chronic diseases. Chronic diseases are seen as being due to “lifestyle”, while infectious diseases are seen as something outside of our control. Unfortunately there’s little evidence to support that view, and even less evidence that focusing our efforts on infectious diseases will result in better health or longevity in Canada or abroad.

Category: Cancer, Determinants of health, Guest Posts, Health systems, Industry, Infectious disease, Nutrition | Tagged , , , , , , , , , , | Leave a comment

What is the scariest disease? Depends how you define scary.

IMG_20141029_144136Whether you’re personally afraid of Ebola or not, you have to admit it’s a scary disease: no vaccine, no cure, and high fatality rate are just a few of its distinguishing features. Recently I polled my friends on what diseases they were afraid of, and many of the ones that made the list were things like cancer and alzheimer’s, conditions that can’t be easily prevented or cured, and that have a high likelihood of developing agonizing symptoms.

While public health priorities should focus on the largest or fastest-growing threats, fear is a personal thing that doesn’t always match up with objective numbers. Influenza kills more people each year than Ebola ever has, but that doesn’t automatically make it scarier. Here, I’ll take a look at a few ways to rank how “scary” a disease might be:

1. How likely am I to die of it?

2. If I catch the disease, is death inevitable?

3. How contagious/infectious is the disease?

 

How likely am I to die of it?

Total fatalities are a good place to start, if only to show off how backwards our intuition can be. If something is responsible for a lot of deaths in absolute numbers, it means it’s a high percentage of total deaths, and thus, more likely that you will die of it. So what are the major killers worldwide?

From the World Health Organization

From the World Health Organization

Only three of the top ten are infectious diseases: lower respiratory infections (think pneumonia), HIV/AIDS, and diarrheal diseases, which include the likes of rotavirus, E. coli, and cholera. If you want to rank specific germs, the top three are:

1. HIV (AIDS) – 1.6 million deaths in 2012

2. Mycobacterium sp. (tuberculosis) – 1.46 million deaths in 2013

3. Plasmodium sp. (malaria) – 627,000 deaths in 2012

Selected honorable mentions, for comparison:

* Influenza: estimated range of 250,000-500,000 each year  (there is a vaccine for this, about 60% effective)

* Pertussis: 195,000 deaths each year  (there is a vaccine for this, 80-90% effective depending on age but decreasing over time)

* Measles: 122,000 deaths each year  (there is a vaccine for this, 95% effective)

* Ebola can’t keep up in this category. Through 2013 it caused only 41 deaths per year. The current outbreak stands at 4,877 deaths as of October 22, although if it’s not contained it has the potential to climb high on our list. See this essay on the potential for Ebola to become endemic in Africa. You want scary? That’s scary.

That said, your chance of dying of anything is only about 1% per year. Let’s keep our focus on infectious diseases and look at a scarier statistic…

 

If I catch the disease, is death inevitable?

There’s a metric for that: the case fatality rate, or CFR. (As in, how many cases of this disease result in fatality?)

Several diseases have horror-movie-ready CFR’s of 100 percent or close to it:

  • Creutzfeld-Jakob (the human version of mad cow)
  • Kuru, another prion disease
  • Naegleria, the brain eating amoeba
  • Rabies (untreated—the typical treatment is to administer rabies vaccine after exposure but before the patient starts showing symptoms. There are no official numbers on the effectiveness of this vaccine, but anecdotally it’s close to 100%).

Some other high CFR diseases:

  • Inhalational anthrax – 93%
  • HIV, if untreated, in developing countries – 80-90% mortality within 5 years
  • Ebola – 71% in the current outbreaks, according to the best estimates.
  • MERS-CoV, an emerging disease that is related to SARS and associated with camels: 45%

Does Ebola’s CFR surprise you? The current outbreak has twice as many cases as deaths, which would seem to put the CFR around 50%. But it’s tricky to calculate CFR for outbreaks that are ongoing and even growing, since the total cases include people who will die, but haven’t yet. Example: say you open an Ebola clinic and admit ten patients, seven of whom will die. If nobody is dead by the end of the day, you might say the CFR is 0%. Next week, if five of them have died, you would calculate the CFR at 50%, and in the meantime maybe you’re admitting five new patients, which instantly drops the rate to 33% (5 out of 15). But if you track those original ten patients over time, you’ll get the right answer – 70%. Here is a discussion of current estimates of Ebola’s CFR.

 

How infectious/contagious is it?

Let’s be clear: these are two different questions. Something is very infectious if it takes very few germs (virus particles, bacterial spores, etc) to trigger disease. Ebola is extremely infectious; so is inhaled anthrax.

A disease’s contagiousness, on the other hand, doesn’t count individual microorganisms, but rather describes how quickly it spreads. Say you share a funny cat picture on facebook and it’s so good that ten friends post it on their walls. Ten of each of their friends post it, and ten of theirs, and so on; that picture will eventually be all over the internet. But if you share a funny picture of your lunch instead, and most people who see it (are “exposed” in epidemiology speak) don’t bother to pass it on, that meme will soon fizzle out.

In epidemiological terms, our funny cat picture has a basic reproduction number, or R0 (pronounced “R naught”) of 10. Our lunch picture, somewhere near zero. An infectious disease needs at least an R0 of 1 to spread; that would mean each person spreads it to one other person. Ebola’s R0 is somewhere around 2; think of the Dallas patient that spread the disease to two health care workers. That’s a typical case.

Measles clearly gets the gold in this contest, with an R0 of up to 18. That means that, in many outbreaks, each sick kid was infecting an average of 18 friends. Here’s a ranking from Wikipedia, taken from published data on each entry:

 Values of R0 of well-known infectious diseases

Disease

Transmission

R0

Measles

Airborne

12–18

Pertussis

Airborne droplet

12–17

Diphtheria

Saliva

6–7

Smallpox

Airborne droplet

5–7

Polio

Fecal-oral route

5–7

Rubella

Airborne droplet

5–7

Mumps

Airborne droplet

4–7

HIV/AIDS

Sexual contact

2–5

SARS

Airborne droplet

2–5

Influenza
(1918 pandemic strain)

Airborne droplet

2–3

Ebola
(2014 Ebola outbreak)

Bodily fluids

1-2

 

Important public health message: Note that the top seven diseases on this list are vaccine-preventable. If you get your kid the MMR and DTaP-HepB-polio shots, that’s all seven (plus tetanus and hepatitis B as a bonus) prevented with just two jabs of the needle. Not a bad deal.

 Here’s a good explainer on the difference between infectious and contagious (and, bonus: the difference between isolation and quarantine).

 

Bottom line

Which diseases are the scariest? It depends on what scares you. Ebola ranks high for its case fatality rate alone. HIV made all of our short lists, and it’s still not preventable, although treatments are available that can mitigate symptoms for years. Heart disease and stroke are more likely to kill you than any disease, but if you have a choice of what to catch, your odds are better with the flu than with kuru or brain-eating amoebas—which are, thankfully, rare. But ultimately, it’s up to you to decide what disease should be the star of your next nightmare.

Fun fact: The disease in the 1995 movie Outbreak was not Ebola, but the fictional “Motaba virus.” Symptoms were Ebola-like but it had a 100% case-fatality rate and airborne transmission. I’m unaware of any calculations of its R0; anybody want to watch it and run the numbers?

 

 

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