Whether for work or for play, on a couch or in a car, being sedentary is correlated with some cancers. (Bigstock)

THE QUESTION Spending too much time sitting — in front of a TV or computer, in the car or at a desk at work, for instance — has been linked to increasing rates of obesity, diabetes and heart disease. Might being sedentary also lead to cancer?

THIS STUDY analyzed data from 14 studies that assessed the time people spent being sedentary, whether due to their job or as part of their recreation. The studies involved 4,068,437 people, including 68,936 with cancer diagnoses. Those who were the most sedentary were 24 percent more likely to have colon cancer than the least sedentary people. The most sedentary women, compared with the least sedentary, had a 32 percent increased risk for endometrial cancer.

For both cancers, risk increased as sitting time rose, up 8 percent for colon cancer and 10 percent for endometrial cancer for every two-hour increase in time spent sitting each day. Those who had the highest risk for these two cancers spent the most time watching TV, creating a 54 percent greater chance of having colon cancer and a 66 percent increased risk for endometrial cancer, compared with those who spent the least amount of time sitting in front of a television. Lung cancer risk also was higher, 21 percent so, among the most sedentary people.

However, no correlation was found between sedentary behavior and breast, ovarian, prostate, stomach, esophageal, testicular or renal cell cancer or non-Hodgkin lymphoma.

What goes wrong in our bodies when we park ourselves for nearly eight hours per day? A chain of problems from head to toe.

WHO MAY BE AFFECTED? People who generally spend a lot of time sitting. Often, time spent on sedentary activities is instead of — rather than in addition to — time spent being physically active, which can lead to weight gain and obesity. Both are risk factors on their own for various cancers. Some studies also have found that people who sit a lot die sooner than expected.

CAVEATS Behavioral data came from participants’ responses on questionnaires or in interviews; none of the studies used accelerometers or other devices to record activity.

FIND THIS STUDY July issue of the Journal of the National Cancer Institute, jnci.oxfordjournals.org.

LEARN MORE ABOUT excess sitting’s risks at www.mayoclinic.org. Find basic information on cancer at www.cancer.org (click on “Learn About Cancer”).

The research described in Quick Study comes from credible, peer-reviewed journals. Nonetheless, conclusive evidence about a treatment's effectiveness is rarely found in a single study. Anyone considering changing or beginning treatment of any kind should consult with a physician.