Adults who spend 11 or more hours a day sitting are at a 40% increased risk of dying in the next three years compared with those who sit for fewer than four hours, the largest study of ageing in the Southern Hemisphere has found.
Researchers from the University of Sydney assessed self-reported data from 22,497 men and women 45 years or older, as part of a larger analysis of ageing among more than 200,000 people across Australia.
After taking into account factors such as gender, age, weight, physical activity and health status, they determined sitting for long hours was associated with a much higher death risk.
The study is published today in Archives of Internal Medicine.
“That morning walk or trip to the gym is still necessary,” said study lead author Hidde van der Ploeg, a Senior Research Fellow at the University of Sydney’s School of Public Health. “But it’s also important to avoid prolonged sitting. Our results suggest the time people spend sitting at home, at work and in traffic should be reduced by standing or walking more.”
The results are the first landmark findings to be published from the Sax Institute’s 45 and Up Study, the largest ongoing study of healthy ageing in the Southern Hemisphere.
They show that physical activity is still beneficial: inactive people who sat the most had double the risk of dying within three years than the active people who sat least. And among the physically inactive group, those who sat the most had nearly one-third higher chance of dying than those who sat least.
The study’s size and focus on total sitting time make it an important contributor to the growing evidence on the downsides of prolonged sitting, Dr van der Ploeg said. The average adult spends 90% of all leisure time sitting down and less than half of adults meet World Health Organization physical activity recommendations.
David Dunstan, Associate Professor and Laboratory Head of Physical Activity at Baker IDI Heart & Diabetes Institute, said the research was “another study confirming consistent associations between too much sitting and an increased risk of premature mortality. Internationally, this is one of the largest by sample size ever conducted.
"The time has come for us to take notice of this insidious health hazard and explore possible solutions to re-engineer more movement back into the work day, and less sitting.
"Providing workers with a choice to work in a seated or upright posture holds great promise in achieving these objectives.”
Traditionally, he said, the focus had been on encouraging people to exercise more. So someone who did 30 minutes of brisk walking on most days met the public health guideline for minimum activity. But this still left about 15 hours of waking time each day during which, for most adults, sitting was the predominant position.