Sitting for hours linked to early death - exercise incapable of reversing effects

Sedentary behaviour is among the highest causes of early death. [iStockphoto]

Who knew a cushy desk job or habitual TV watching and social media scrolling could be super hazardous? It turns out that sitting all the time isn’t how humans were meant to live.

Researchers from the University of California-San Diego suggest that sedentary behaviour is among the highest causes of early death. Older women who sat for 11 hours or more daily saw their risk of death jump by 30 per cent, even if they exercised vigorously!

According to the 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 forms of exercise showed the same heightened risk as long as they sat for long hours.

“If one takes a brisk long walk for an hour but sits the rest of the day, they will still accrue all the negative effects on their metabolism,” study co-author Steve Nguyen, a postdoctoral fellow at the UC San Diego Herbert Wertheim School of Public Health and Human Longevity Science.

It’s an alarming conclusion, but Nguyen used an impressive sample size for the research. The team examined up to 6,489 women (ages 63 to 99) who wore monitors showing the time they spent sitting and their daily activity measurements. They tracked the participants for eight years, monitoring if any of the women died.

That data was originally collected from a larger long-term national project called the Women’s Health Initiative (WHI), which began in 1991 and is still ongoing. This report is the first ever to utilize a novel and validated machine-learned algorithm (called CHAP) to analyse the relationship connecting total sitting time and length of sedentary activity with the risk of premature death.

“Sedentary behaviour is defined as any waking behaviour involving sitting or reclining with low energy expenditure,” Nguyen says in a university release.

“Sedentary behaviour, in general, isn’t healthy because it slows down muscle contractions, blood flow, and glucose metabolism.”

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“When sitting, blood flow throughout the body slows down, decreasing glucose uptake. Muscles aren’t contracting as much, so anything that requires oxygen consumption to move the muscles diminishes, and the pulse rate is low,” Dr Jeila Mohamed, a cardiology specialist at the Agha Khan University Hospital explains. Mohamed was not a part of the research team.

So, what can you do if you sit too long? Nguyen says that not all sitting is the same.

“The risk starts climbing when you’re sitting for over 11 hours per day, and how much longer you sit in a single session. Sitting more than 30 minutes at a time is associated with higher risk than sitting only ten minutes at a go. 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, but just stroll about for a little while,” Nguyen recommends.

The study is published in the Journal of the American Heart Association.