SAN DIEGO — Who knew a Netflix binge or cushy desk job could be so hazardous? Researchers from the University of California-San Diego suggest that avoiding sedentary behavior (like sitting down all day) may be the secret to a longer life. Older women who sat for 11.7 hours or more daily saw their risk of death jump by 30 percent – even if they exercised vigorously!
It’s an alarming takeaway, but study co-author Steve Nguyen, a postdoctoral fellow at the UC San Diego Herbert Wertheim School of Public Health and Human Longevity Science, used an impressive sample size for his work. His team examined time spent sitting and daily activity measurements collected from monitors worn for up to a week by 6,489 women (ages 63 to 99). Researchers also tracked the participants for eight years, monitoring if any of the women died.
That data was originally collected during a study led by Andrea LaCroix, Distinguished Professor at the Herbert Wertheim School of Public Health. It’s a larger long-term national project called the Women’s Health Initiative (WHI), which began in 1991 and is still ongoing today. This report is the first ever to utilize a novel and validated machine-learned algorithm (called CHAP) in order to analyze the relationship connecting total sitting time and length of sedentary activity with the risk of premature death.
“Sedentary behavior is defined as any waking behavior involving sitting or reclining with low energy expenditure,” Nguyen says in a university release. “Previous techniques for calculating sedentary behavior used cut points that identified low or absent movement. The CHAP algorithm was developed using machine-learning, a type of artificial intelligence, that enhanced its ability to accurately distinguish between standing and sitting.”
Exercise ‘incapable’ of reversing the damage
Fine-tuning “sitting” helped Nguyen separate and better assess total sitting time and usual sitting bout durations. Sedentary behavior, in general, isn’t healthy because it lowers 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,” Prof. LaCroix explains.
Unfortunately, and rather surprisingly, exercise appears incapable of reversing these negative effects. According to researchers, whether women participated in low or even high amounts of moderate-to-vigorous intensity physical activity ultimately proved inconsequential if paired with excessive sitting; all patterns of exercise showed the same heightened risk if they also 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,” Prof. LaCroix continues.
So, what can you do if you sit too long?
Notably, Nguyen also says that not all sitting is the same.
“Looking beyond conditions like cardiovascular disease, we start thinking about cognitive outcomes, including dementia,” the researcher explains. “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 recently received a National Institute of General Medical Sciences K99 award entailing 12 months of mentored research focusing on protein signatures tied to physical activity and how they relate to dementia. Prof. LaCroix, meanwhile, while sympathetic to the challenges of changing sedentary behavior once habits set in, also stresses that the modifications are frequently necessary.
“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. 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,” Prof. LaCroix concludes.
