Adults who sit for long periods may face a higher risk of Type 2 diabetes than individuals who move around more often, a new review concludes.
Even adults who met guidelines for physical activity risked compromising their health by sitting for prolonged periods, say researchers who estimated that sitting behaviour was associated with double the risk of diabetes.
The study was published in Monday's issue of Diabetologia, the journal of the European Association of the Study of Diabetes.
"The average adult spends 50-70 per cent of their time sitting, so the findings of this study have far-reaching implications," said the study's lead author, Dr. Emma Wilmot, a clinical research fellow in diabetes and endocrinology at Leicester General Hospital in the U.K.
"By simply limiting the time that we spend sitting, we may be able to reduce our risk of diabetes, heart disease and death," she added in a release.
For the review, Wilmot and her co-authors combined the results of 18 studies involving more than 794,000 adults in the U.S., Canada, Australia, Europe and Japan.
They said the associations between the most prolonged sitting and poorer health held after considering moderate-to-vigorous levels of physical activity, which suggests the risks of sedentary behavior are distinct.
The studies all measured prolonged sitting differently, such as watching TV less than one hour a day compared to more than seven hours a day, or watching TV and driving a car for less than 11 hours a week, versus more than 23 hours a week.
The investigators speculated on several potential reasons for the association, such as differences in enzyme activity in muscles that help maintain posture and insulin sensitivity in skeletal muscle.
Most research aimed at reducing screen time has been aimed at young people, the researchers said. They recommended that future diabetes prevention programs consider promoting reduced sedentary behavior alongside increasing physical activity levels and dietary changes.
Co-author of the study, Prof. Stuart Biddle of Loughborough University, suggested some ways to reduce sitting time:
Breaking up long periods at the computer at work by placing a laptop on a filing cabinet.
Conducting standing meetings.
Walking during lunch breaks.
Reducing TV viewing time in the evenings and doing less sedentary activities instead.
The review was limited by drawbacks in how some of the studies were designed, such as relying on self reports of sedentary time instead of objective measurements. Only studies published in English were included.
The researchers cautioned that the studies found no cause-and-effect can be inferred and that people in poorer health may sit longer than those who are healthier.
A study published earlier this year in the journal BMJ Open concluded that reducing sitting time to less than three hours per day could increase life expectancy in the U.S. by two years, assuming there is a cause-and-effect relationship between sedentary behaviour and death. Similarly, a 2006 study estimated that lack of physical activity during leisure time accounts for about 0.9 years of life expectancy at birth in Canada.
The U.K. research was funded by National Health Service trusts at the University Hospitals of Leicester and Loughborough University, and the U.K.'s National Institute for Health Research.