Physical Activity Negates Mortality Risk of Excessive Sitting

Too much sitting has been linked to shortened life spans but it was previously unclear if there was a way to offset the risk aside from not sitting for so long. The results of a new study published in the Journal of the American College of Cardiology show increasing physical activity to recommended levels eliminates the association in all but the worst cases of excess sitting.

Researchers in Australia conducted a study to better understand the association between sedentary behavior and physical activity as it relates to mortality. They also wanted to better understand the effects of replacing sitting with standing, moving and sleep.

Emmanuel Stamatakis, Ph.D., professor of physical activity, lifestyle and population health at the University of Sydney in Australia and lead author of the paper said, "Previous studies have not considered that a 24-hour day is finite and an increase in any type of physical activity or sedentary behavior would displace another activity or sleep."

The pool of participants included more than 149,000 Australian men and women aged 45 and over. They were asked to complete a questionnaire to categorize how many hours per day they spent sitting, standing and sleeping. They were also queried about the amount of time they spent walking or engaging in moderate or vigorous physical activity.

Daily sitting time was broken down into four categories: less than four hours, four to six hours, six to eight hours and more than eight hours. Weekly physical activity was broken down into five categories: inactive (no physical activity), insufficiently active (1-149 minutes), sufficiently active at the lower limit of Australian recommendations (150-299 minutes), sufficiently active at the upper limit (300-419 minutes) and highly active (420 minutes or more). The highly active group averaged more than one hour of physical activity per day.

More than 8,600 participants died during the mean 8.9 year follow up period. It was determined higher sitting times of more than six hours per day were associated with higher all-cause and cardiovascular disease mortality, but mostly in those who did not meet the physical activity recommendations.

Among those who met even the lowest requirements for physical activity the association with all- cause mortality was eliminated except among those who sat for more than eight hours per day. More evidence to underscore the importance of exercise was found in comparing those who sat for less than four hours per day. The ones who registered no activity were at a substantially elevated risk compared to those who exercised the most.

"Our results support continued efforts to promote physical activity in those segments of the population that sit a lot for whatever reason," Stamatakis said. "In the absence of some physical activity, merely reducing sitting times may be insufficient for better health."

Click here to read more in the Journal of the American College of Cardiology.