Risk of death increased by 30% for older women who sit for 11.7 hours or more per day, regardless of whether they exercise vigorously.
Bad news for couch potatoes! A new study published in the Journal of the American Heart Association (JAHA) has data showing that sedentary behavior increases mortality risk. The study was led by Andrea LaCroix, Ph.D., M.P.H., Distinguished Professor at the Herbert Wertheim School of Public Health, and was partially funded by the National Institutes of Health as part of a 3+ decades long national project known as the Women’s Health Initiative (WHI).
Study co-author Steve Nguyen, Ph.D., M.P.H., a postdoctoral fellow at the University of California San Diego Herbert Wertheim School of Public Health and Human Longevity Science, examined measurements of sitting and daily activity collected from hip devices worn for up to seven days by 6,489 women, aged 63 to 99, who were followed for eight years for mortality outcomes. Results show that older women who sat for 11.7 hours or more per day increased their risk of death by 30 percent, regardless of whether they exercised vigorously.
Sedentary behavior is a health risk because it reduces muscle contractions, blood flow and glucose metabolism. “When you're sitting, the blood flow throughout your body slows down, decreasing glucose uptake. Your muscles aren't contracting as much, so anything that requires oxygen consumption to move the muscles diminishes, and your pulse rate is low,” said LaCroix.
Unfortunately, exercise cannot undo these negative effects. According to the study, whether women participated in low or high amounts of moderate-to-vigorous intensity physical activity, they showed the same heightened risk if they sat for long hours.
“If I take a brisk long walk for an hour but sit the rest of the day, I'm still accruing all the negative effects on my metabolism,” said LaCroix.
Based on the research, LaCroix makes the following recommendation: “The risk starts climbing when you’re sitting about 11 hours per day, combined with the longer you sit in a single session. For example, sitting more than 30 minutes at a time is associated with higher risk than sitting only 10 minutes at a time. Most people aren't going to get up six times an hour, but maybe people could get up once an hour, or every 20 minutes or so. They don't have to go anywhere, they can just stand for a little while.”
However, Nguyen points out that not all sitting is the same. “Looking beyond conditions like cardiovascular disease, we start thinking about cognitive outcomes, including dementia,” he said. “There are cognitively stimulating activities that can result in sedentary behavior, like sitting while studying a new language. Is sedentary behavior in that context overall bad for a person? I think it's hard to say.” Nguyen has recently received a National Institute of General Medical Sciences K99 award for 12 months of mentored research to look at protein signatures of physical activity and how they relate to dementia.
“We've created this world in which it's so fascinating to sit and do things. You can be engrossed by TV or scroll on your Instagram for hours," says LaCroix. But sitting all the time isn't the way we were meant to be as humans, and we could reverse all of that culturally just by not being so attracted to all the things that we do while sitting.”