Can how you sit help lower your cancer risk?

mom and daughter practicing yoga to stay active

We know not only that moving is good for us but also that sedentary behavior independently contributes to a host of bad health outcomes: obesity, diabetes and heart disease are the most frequently mentioned in the medical literature. But perhaps surprisingly, cancer is also on this list, and has been on this list for quite some time.

Almost 50 years ago researchers noticed that sedentary jobs were associated with a substantially increased risk of colon cancer1. Since that first report sitting has been found to increase the risks of several other cancers: a recent review2 found that not only colon cancer but also ovarian, endometrial, breast and prostate cancers were also more common in people who were more sedentary. Moreover, these effects are not small: cancer rates increased by as much 8% (ovarian) to 25% (colon). Worst of all, because these are serious cancers, overall deaths from cancer were 18% more common in people who were the most sedentary.

While it's not certain how sedentary time contributes to developing cancer, there are at least three plausible physiologic explanations. First, sedentary time is associated with obesity, and fat cells are the main source of aromatase, an enzyme associated with estrogen production, setting the stage for gynecological cancers. Additionally, sedentary time is associated with insulin resistance and consequently increased levels of insulin-like growth factor (IGF-1) which is a known mitogen. Finally, both obesity and sedentary behavior increase systemic inflammation, an independent risk factor for several cancers. And of course, all of these factors may be contributing simultaneously, creating a “perfect storm” with a possible malignant outcome.

Because sedentary behavior is such an important risk factor for developing cancer the public health community has tried hard to find ways to encourage us all to be more active and less sedentary. The governments of the UK, New Zealand, Germany, and Australia all now recommend “minimizing the time spent in prolonged sitting” or to simply “sit less”. Unfortunately, simply recommending that people “sit less” is likely to be ignored along with most other well-intentioned but bloodless governmental recommendations.

Actually, we know these recommendations will likely be ignored, because a recent paper by Lam and associates3 reviewed interventions that have been tried to inject more movement into office workers’ days, and concluded that changing the physical environment in a way that encourages activity is the single most effective strategy. Yes, you can try to influence personal behavior by exhorting or rewarding or berating them, but people easily forget to move or simply don’t want to; changing the physical environment, on the other hand, is non-negotiable. Because Lam’s paper was a high-level review of over 100 individual studies it doesn’t expand on which changes to the physical environment might most effectively increase movement, but I suspect when this question is studied active sitting will turn out to be one of the best ways to keep people moving, and healthier, at work.

1Sedentary jobs and colon cancer

2Sedentary behavior and cancer-an umbrella review and meta-analysis

3How effective and how expensive are interventions to reduce sedentary behavior? An umbrella review and meta-analysis

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