Older women spend about two-thirds of their time sitting, a new study suggests.
Sedentary behavior has been linked to disease and disability. That's in part because people who spend lots of time sitting also tend to not meet physical activity guidelines - but it's not the whole story.
"Even people who go to the gym every day and run 6 miles on a treadmill can be at risk for bad outcomes from being sedentary if they spend 8-10 hours seated at a desk and then watch TV with their spouse after dinner," said Dr. Catherine A. Sarkisian in an email.
Sarkisian is the director of the Los Angeles Community Academic Partnership for Research in Aging Center and a geriatrician at UCLA. She was not involved in the new report.
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Researchers led by Eric J. Shiroma from the Harvard School of Public Health in Boston gave about 7,200 women devices to measure how much they moved around during the day. The women, in their early 70s, on average, wore the so-called accelerometers for a week.
Participants spent about two-thirds of their waking time - or just under 10 hours each day - being sedentary. That most likely meant they were sitting but could reflect time spent standing still as well, Shiroma and his colleagues wrote Tuesday in the Journal of the American Medical Association.
The researchers found older and heavier women were more likely to spend large portions of their day being sedentary.
Most "bouts" of sedentary behavior were short, and women tended to get up and start moving regularly throughout the day. About one-third of their sedentary time was spent being totally inactive for at least a half hour.
Shiroma said he was surprised participants were generally sedentary for only short periods at a time.
"Most of us had thought that people were sitting a lot longer, and maybe people who are sitting a lot longer are at greater risk, but we're going to have to wait and see," he said.
"We don't necessarily know where the threshold is for, how long is sitting too long?"
It's also not clear whether what really matters is how much total time people spend being sedentary throughout the day or how many breaks they take to walk around and how often, Shiroma added.
"I think this is an interesting finding and I like that it challenges the old stereotype of the senior citizen just hanging out in her rocking chair doing nothing meaningful," Sarkisian said of the short sedentary bouts.
Many older people participate in a wide range of activities in their communities, she said. Walking is an especially accessible way to get exercise in old age.
"Being sedentary should not be accepted as a normal part of aging," Sarkisian said.
Most women in the study were white and relatively well-off, the researchers noted. So it's not clear if sedentary behavior would be the same among women of other races or poorer women.
Shiroma said they plan to continue following the participants to see whether sedentary time ends up being linked to women's risk of heart disease, diabetes and other conditions.