Sitting at Leisure Is a Dangerous Occupation

The importance of physical activity took a hit a few days ago, when I posted a piece saying that obesity was a greater risk factor than lack of exercise in raising blood pressure.  Now there’s another study that shows that physical activity is less relevant in reducing mortality than avoiding spending time sitting.  It’s published in the online edition of the American Journal of Epidemiology. 

The American Cancer Society enrolled over 53,000 men and 69,000 women to complete questionnaires on various aspects of their health and lifestyle.  The participants were 50-74 years old when the study began in 1992;  they were asked, "During the past year, on an average day (not counting time spent at your job), how many hours a day did you spend sitting (watching television, reading, etc.)?"  Mortality was recorded over the next 14 years.

After adjusting for smoking, body mass index (BMI), and other factors, it was found that, compared with sitting less than 3 hours a day, sitting 6 or more hours a day was associated with an increased death rate by 34% in women and 17% in men.  There was an increased death rate by 94% in the least active women and by 48% in the least active men. These associations were strongest for cardiovascular mortality, followed by cancer deaths. 

What’s interesting about these results is that the time spent sitting was independently linked to total mortality, regardless of the physical activity level.  It’s becoming clear that we have to tackle a healthy lifestyle on many fronts, not just by boosting our gym time.