Why do we get less healthy as we age?

Image cred: SG-Works

The clock is ticking…
Image cred: SG-Works

As we get older, we almost inevitably experience health problems. Whether it’s a specific disease, such as cancer, or a general decline in physical and mental functioning, the accumulation of years we spend on this earth results in wear and tear to our bodies. Several cancers often develop due to multiple “hits” to our genomes by environmental factors such as smoking, chemical exposures, and stress, which add up over our lifetimes to literally leave a biological footprint on our bodies through causing genetic aberrations. This is an example of how the trendy scientific concept of ‘gene-environment interactions’ works in causing disease. Another example is that of telomeres – like the plastic bit on the end of a shoelace, telomeres are the bits of DNA at the end of our chromosomes. They protect against loss of genetic code when our cells divide, and are thought to hold the secrets to human ageing. But, I digress – if you want to read more about telomeres, click here (1), here (2), or here (3).

It’s easy then to feel defeated and accept that things will get worse as we get older.  We begin life pristine, with soft fresh skin and strong bodies and minds. I’m in my mid-twenties, and can already feel the loss of my teenage metabolism, energy levels, and sun damage-free skin. Will it only get worse from here? Maybe it will, but maybe not. The wear and tear of ageing seems inevitable, but many other negative health effects of ageing may not be.

How many of the ill health effects of ageing are due to the specific social and material environments of the world we live in today?

Because our world is constantly changing with each generation that inhabits it, the exposures that we encounter often in turn vary by generation. Subsequently, comparing disease rates and exposures across birth cohorts may provide us with some clues to the causes of poor health and their historical explanations.

Image Cred: Cancer Research UK

Trends in smoking and lung cancer in men and women
Image Cred: Cancer Research UK

The most classic example of an environmental exposure (when I say “environment”, I mean literally anything outside of the body – such as a chemical agent, a lifestyle practice, or even the broader social, economic, or political environment) and its related health outcome changing over time is cigarette smoking and lung cancer. See the above graph for the changing rates of cigarette smoking over the latter half of the 20th century for men and women in the United Kingdom – and the striking mirroring of lung cancer rates 20-30 years later. Since women began smoking later than men – for reasons including social acceptability and appearance that also related broadly to feminist movements in the mid-20th century – you can see how the curves are different for women. As you can see, lung cancer rates are decreasing among men, while we are still under the peak of high lung cancer among women due to the above social reasons. Clearly, this historical explanation of smoking rates explains lung cancer rates today, which are of course socially contingent and not inevitable.

Although we don’t need these graphs to know that smoking causes lung cancer, this type of research is useful for understanding what we don’t know about health in contemporary times. In the early 1990s, there was an epidemic of suicides among young adults in Australia. Recent research attempted to understand whether this rise in suicide rates was because Australians born in certain years were more likely to commit suicide, or whether there was something particular about Australia in the 1990s that made people commit suicide regardless of when they were born (the authors hypothesised that high unemployment rates were the culprit), or whether people are more likely to commit suicide as young adults, regardless of when they were born or when they died (4). Using statistical methods to separate out the effects of birth year, age, and time period, the study found that men born after 1970-74 were more likely to commit suicide than those born before then (4). Men in this age group were subject to high unemployment and unstable employment, which may in part explain the suicide rates. A definite causal link cannot be made with this research, but it adds to our knowledge about what happened and can help with future predictions about the consequences of economic uncertainty.

So, it appears that some of the health problems we encounter today are not inevitable and always have historical and social reasons. Maybe I can’t avoid losing my metabolism and gaining wrinkles over time – but I can avoid eating the plethora of sugary, processed foods which are ubiquitous in the food system today.  I can also avoid tanning my skin, the consequences of which are becoming clear, as rates of melanoma skin cancer are currently rising. Obesity will become known as a major global health problem of our time. Last week, it was announced that 2.1 billion people in the world are overweight or obese (5). Why is this happening? Are humans more sedentary than we were twenty, fifty, or one hundred years ago? What has changed in our overall social structure to cause this tipping of our individual energy systems to be, on the whole, in a surplus? Sugar and processed foods probably have something to do with it. What else can you think of? A bit of scientific evidence, combined with critical and creative thought can help you to understand the crazy world we live in today, and how it affects your own body and health.

References

  1. Seigel LJ. Are telomeres the key to aging and cancer? http://learn.genetics.utah.edu/content/begin/traits/telomeres/ (accessed 30 May 2014).
  2. Heidinger BJ, Blount JD, Boner W, Griffiths K, Metcalfe NB, Monaghan P. Telomere length in early life predicts lifespan. PNAS 2012;109:1743-8.
  3. Shammas MA. Telomeres, lifestyle, cancer, and aging. Curr Opin Clin Nutr Metab Care 2012;14:28-34.
  4. Page A, Milner A, Morrell S, Taylor R. The role of under-employment and unemployment in recent birth cohort effects in Australian suicide. Soc Sci Med 2013:93:155-62.
  5. Ng M, Fleming T, Robinson M, Thomson B, Graetz N, Margono C, et al. Global, regional, and national prevalence of overweight and obesity in children and adults during 1980-2013: a systematic analysis for the Global Burden of Disease 2013. Lancet 2014. doi: 10.1016/S0140-6736(14)60460-8

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Why do we get less healthy as we age? by Public Health, unless otherwise expressly stated, is licensed under a Creative Commons Attribution 3.0 Unported License.

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One Response to Why do we get less healthy as we age?

  1. Alyssa Gilinsky says:

    Great blog post but one nitpick is the use of ‘commit’ to discuss suicide rates. Suicide is not a crime and this language use continues the stigma associated with thought about killing oneself, which may ultimately lead to people avoiding help-seeking. In future, using terms like numbers died by suicide or rates of suicide death would solve this problem. Thanks again for an informative post.

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