No Really – Sitting Is Killing You

Grim Reaper From Guitar Hero - Halloween (2006)
Earlier this year I posted an infographic on the health impact of sedentary behaviour which has generated plenty of discussion both here and elsewhere.  Many people are understandably skeptical about the relationship between sedentary behaviour and mortality, so I was excited about the recent publication of two recent systematic reviews focusing on just this issue.

The first, published in the American Journal of Preventive Medicine by Karin Proper and colleagues, focused on the prospective association between sedentary behaviour and obesity, CVD and diabetes risk, as well as mortality.  Somewhat surprisingly, they found little evidence that sedentary behaviour was associated with increased body weight or other health risk factors, despite consistent associations between sedentary behaviour and risk of death.  From the paper:

Weight Gain:

Based on the inconsistent findings among the [3] prospective studies identified, there is insufficient evidence for a longitudinal relationship between sedentary behavior and body weight/BMI gain.

Risk of Being Overweight or Obese:

Based on the inconsistent findings among the [4] studies, there is insufficient evidence for the relationship between sedentary behavior and the risk for overweight or obesity.

Increased Waist Girth:

Based on this single study, there is insufficient evidence for the relationship between sedentary behavior and waist gain.

Risk of Developing Diabetes:

Based on the consistent findings of… two low-quality studies, there is moderate evidence for a significant positive relationship between the time spent sitting and the risk for type 2 diabetes.

Risk of Cardiovascular Disease:

Based on the findings of the 4 studies identified, there is insufficient evidence for a significant relationship between sedentary behavior and various CVD risk factors.

Endometrial Cancer:

Based on the inconsistencies found between and within the two studies identified, there is insufficient evidence for the relationship between sedentary behavior andendometrial cancer.

As I said, there’s really not much evidence so far that sedentary behaviour is prospectively linked with these various markers of health.  However, it does seem to be associated with increased risk of death from various causes:

Based on the findings of the two high-quality studies, there is strong evidence for a relationship between sedentary behavior and mortality from all causes and from CVD, but no evidence for the relationship between sedentary behavior and mortality from cancer.

Another review published late last year focused specifically on sedentary behaviour and cancer outcomes.  It’s conclusions were a bit stronger than the review above, but the evidence for a relationship between sedentary behaviour and cancer still seems pretty weak.  From the review:

The literature review identified 18 articles pertaining to sedentary behavior and cancer risk, or to sedentary behavior and health outcomes in cancer survivors. Ten of these studies found statistically significant, positive associations between sedentary behavior and cancer outcomes. Sedentary behavior was associated with increased colorectal, endometrial, ovarian, and prostate cancer risk; cancer mortality in women; and weight gain in colorectal cancer survivors. The review of the literature on sedentary behavior and biological pathways supported the hypothesized role of adiposity and metabolic dysfunction as mechanisms operant in the association between sedentary behavior and cancer.

What’s the take-home message?

Sedentary behaviour seems very likely to be associated with increased risk of all-cause and cardiovascular disease mortality, while the relationship between sedentary behaviour and cancer mortality remain quite speculative.  Interestingly, prospective studies have yet to find much strong evidence linking sedentary behaviour with prospective risk of cardiovascular disease, despite being associated with increased risk of cardiovascular disease mortality.  Clearly there’s still a lot to be worked out here, especially given that so few prospective studies have been performed to date.  Further, 17 of 19 studies in the Proper review used self-report measures of sedentary behaviour, which can be dramatically different from directly measured sedentary behaviour.

The prospective relationships between sedentary behaviour and risk markers is likely to become more clear with time.  In the meantime, it seems reasonably clear that the more you sit, the greater your risk of mortality.

Standing workstation, anyone?

Travis

ResearchBlogging.orgProper, K., Singh, A., van Mechelen, W., & Chinapaw, M. (2011). Sedentary Behaviors and Health Outcomes Among Adults American Journal of Preventive Medicine, 40 (2), 174-182 DOI: 10.1016/j.amepre.2010.10.015

To get future posts delivered directly to your email inbox or to your RSS reader, be sure to subscribe to Obesity Panacea.

Related Posts Plugin for WordPress, Blogger...

Creative Commons License
No Really – Sitting Is Killing You by Obesity Panacea, unless otherwise expressly stated, is licensed under a Creative Commons Attribution 3.0 Unported License.

This entry was posted in Obesity Research, Peer Reviewed Research, Sedentary Behaviour. Bookmark the permalink.

4 Responses to No Really – Sitting Is Killing You

  1. Aggie says:

    Are you sure that your bias isn’t affecting your conclusions? I have often wondered about studies that claim they show active people are healthier, have better odds of surviving serious illness, live longer, etc. What if it is the other way around? What if people who are healthier and feel better are more active? As you know, correlation does not prove causation.

    There is also the issue of how some people seem to be naturally active and others seem to be born couch potatoes. Why do some people enjoy being on the move and never seem to sit still while others would prefer to lounge all day? If the couch potatoes are persuaded to move more, will it make a difference in their health? Even while engaged in active games or exercise, why do some find a way to move less than others? So far, I think there are more questions than answers.

    VA:F [1.9.22_1171]
    Rating: 0 (from 0 votes)
    • Travis says:

      Those are excellent questions. In x-sectional studies especially, it’s difficult to tease out whether sitting causes bad health, or bad health causes sitting. Typically mortality studies like these exclude people who are sick or who die very soon after the start of the intervention, in order to try to get around this problem (e.g. if someone already has cancer or heart disease at the start of the study, that may be why they are sitting *and* why they die sooner than their peers).

      There are also now quite a few intervention studies where people or animals are forced to be sedentary for a period of time lasting from hours to months. And in those studies we see effects that would likely contribute to increased risk of chronic disease, and eventually higher mortality.

      All that to say that for the time being, it’s impossible to say how strong the relationship between sedentary behaviour and health are, especially given how few studies have been published in the area. But there’s enough evidence from various fields of research that I’m comfortable concluding that there is at least some impact of sedentary behaviour on health.

      VA:F [1.9.22_1171]
      Rating: 0 (from 0 votes)
  2. Pingback: For The Love Of Food | Healthy Eating Tips - Upgrade Your Healthstyle | Summer Tomato

  3. Pingback: Around the Web; Do You Know Where Your Neurotransmitters Were? Edition | Perfect Health Diet