Sitting Too Long? You May Increase Your Risk of Cancer

African American young woman

What You Need to Know: If you’re spending a lot of time sitting every day, either in front of the TV or at work, you may be at higher risk for developing certain types of cancer, according to new research published this week in the Journal of the National Cancer Institute.

The Evidence: The study found an additional two hours a day of sedentary behavior was linked to an 8% increase in colon cancer risk, a 10% increase in endometrial cancer risk and a 6% increase in risk for lung cancer. It did not find the same connection for breast, rectum, ovary and prostate cancers or for non-Hodgkin lymphoma.

  • Researchers came to these conclusions by analyzing 43 existing studies – that included more than 4 million study participants and 68,936 cancer cases – to measure the relationship between hours spent sitting and certain types of cancers.
  • It’s important to note that while the study identifies a link between sedentary behavior and an increased risk for certain cancers, the research doesn’t prove cause and effect.

“Does sitting in front of the TV cause colon cancer? No,” said Dr. Martin Heslin, chief of surgical oncology at the University of Alabama at Birmingham. “But the recommendations (of the study) are awesome.” Heslin, who was not involved in the research, says that in addition to sedentary behavior, several factors can increase your risk of cancer, including drinking or smoking too much, being obese and having a genetic predisposition.


It’s nearly impossible to say that any one of these factors causes someone to get a specific cancer, he says, but these are the behaviors we can control to help reduce our risk.

“You can affect TV time by turning it off,” said Heslin, though he acknowledges it’s not so easy to turn off work if you’re stuck in an office all day.

In that case, Heslin suggests looking for opportunities to leave your desk, such as standing up while working or taking a walk, to reduce the number of hours you spend sitting down.

“If I ever have the opportunity to design (a meeting room), I’m putting a waist-high table in the room, and no chairs,” Heslin said.

According to an editorial accompanying the study, organizations such as the American Cancer Society and the UK Department of Public Health address the need to reduce hours spent sitting, but do not offer any quantitative recommendations or strategies to help people improve. Daniela Schmid, one of the study’s co-authors and a faculty member in the University of Regensburg’s department of epidemiology and preventive medicine, hopes to change that.

“The findings of our study may encourage public health efforts to expand physical activity recommendations to reduce time spent in sedentary behavior,” Schmid said.

Previous studies support the findings in Schmid’s study. A 2012 study conducted by the National Institutes of Health concluded that sitting for several hours a day is bad for you, even if you are physically active. Researchers found even exercising at least 150 minutes each week – the generally accepted public health guideline for physical activity – can’t reverse the negative effects of sitting down for hours. In that study, sitting increased an individual’s risk for major chronic diseases such as Type 2 diabetes, cardiovascular disease, and breast and colon cancers.

My Take: If you sit regularly, get up periodically (even if that means every 20-30 minutes for a few minutes). In addition, aim for a minimum of 150 minutes per week of the equivalent of a brisk walk (for example, 30 minutes daily for five times per week). I’m Dr. Michael Hunter.

The small print: The material presented herein is informational only, and is not designed to provide specific guidance for an individual. Please check with a valued health care provider with any questions or concerns. As for me, I am a Harvard- , Yale- and UPenn-educated radiation oncologist, and I practice in the Seattle, WA (USA) area. I feel genuinely privileged to be able to share with you. If you enjoyed today’s offering, please consider clicking the follow button at the bottom of this page.

Available now: Understand Colon Cancer in 60 Minutes; Understand Brain Glioma in 60 Minutes. Both can be found at the Apple Ibooks store. Coming Soon for iPad: Understand Breast Cancer in 60 Minutes; Understand Colon Cancer in 60 Minute; Understand Colon Cancer in 60 Minutes; Understand Brain Glioma in 60 Minutes. Thank you.

Reference: CNN Health, 16 June 2014