News in Science

Sitting less may extend livespan

Taking a stand Adults may boost their life expectancy by two years by sitting for fewer than three hours a day, say researchers, although they admit it's a tough task.

The study, which appears in the online journal BMJ Open found that adults spend about 7.7 hours per day engaged in "sedentary behaviour".

"Yes, this would be a challenge," says co-author Peter Katzmarzyk of the Pennington Biomedical Research Centre of the team's proposal to reduce sitting - given the amount of time most people spend behind their desks at work.

"On the other hand, there are many strategies to reduce sitting time, such as standing more at work using a standing desk or treadmill desk, having walking meetings, going to see someone down the hall rather than emailing them etc."

Along with their main finding, the researchers also found that reducing television viewing to less than two hours a day could similarly add 1.4 years.

The research was based on a comparison of population health and lifestyle statistics with polling data on inactivity.

Other studies have linked extended periods of sitting or watching television to diabetes and death from heart disease or stroke.

In 2010, an Australian study led by Associate Professor Dunstan of Baker IDI in Melbourne found television viewing reduced life expectancy at birth by 1.8 years in men and 1.5 years in women.

"We now have some physiological studies showing that when you are sitting, your leg muscles (the largest in the body) are completely inactive, which causes problems with how you handle your blood sugar and how you handle cholesterol," says Katzmarzyk.

"The results of this study indicate that extended sitting time and TV viewing time may have the potential to reduce life expectancy in the USA," the researchers write.

"... a significant shift in behaviour change at the population level is required to make demonstrable improvements in life expectancy."

The paper stresses this was a theoretical estimate, and should not be taken to mean that people who are less active should expect to live 1.4 or two years fewer than the rest.

"Life expectancy is a population statistic and it does not apply to individuals."