Sedentary Lifestyle Linked To Higher Mortality, Study Reveals; Exercise May Not Undo Negative Effects

A new study shows that older women who remained seated for at least 11.7 hours each day had a 30% higher mortality risk, even if they vigorously exercised.

Sedentary Behavior in Older Women

Steve Nguyen, PhD, MPH, a co-author of the study and a postdoctoral fellow from the School of Public Health and Human Longevity Science from the University of California San Diego Hebert, looked into measurements of daily activity and sitting taken from hip devices that 6,489 women wore for seven days. These women participants were aged 63 to 99 years. For eight years, these women were followed to assess outcomes of mortality.

The assessment was noted in the "Prospective Associations of Accelerometer‐Measured Machine‐Learned Sedentary Behavior With Death Among Older Women: The OPACH Study" study. It comes as part of a long-term nationwide project called the Women's Health Initiative (WHI), which started in 1991 and continues until now.

The study is the first to use CHAP, a validated and novel machine-learned algorithm, for examining the total sitting period and sitting bout lengths in relation to death risk. Nguyen explains that sedentary behavior refers to any waking behavior that involves sitting down or reclining with low expenditure of energy.

Nguyen notes that in the past, previous methods for gauging sedentary behavior made use of cut points that distinguished absent or low movement. The algorithm was made through machine learning, which boosted its capacity to accurately differentiate between sitting and standing. Fine-tuning the sitting allowed Nguyen to parse the duration of sitting bouts and total sitting time.

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Sedentary Behavior and Heightened Mortality Risk

Sedentary behavior leads to health risks due to how it reduces blood flow, muscle contractions, and the metabolism of glucose. Andrea LaCroix, PhD, MPH, the study's lead author, explains that when one is sitting down, the blood flow across the body slows down and consequently decreases the uptake of glucose. The muscles do not contract much, diminishing anything that requires the consumption of oxygen for muscle movement. The pulse rate also gets low.

The study notes that these negative effects cannot be undone by exercise. Regardless of whether the women engaged in high or low amounts of vigorous or moderate-intensity exercise, they still exhibited heightened risk if they remained seated for these long hours.

Based on the study, LaCroix recommends certain things. LaCroix notes that the risk goes up when one sits for around 11 hours each day, combined with when a person sits down for a longer duration in a single sitting session. LaCroix adds that while most people do not get up six times in a single hour, they could get up once each hour or every 20 minutes. They do not need to go somewhere; they can just stand up.

However, not all sittings are the same. Nguyen explains that there are cognitive outcomes to be considered, adding that certain cognitively stimulating activities could lead to sedentary behavior. He adds that it is hard to conclude whether sedentary behavior in such a context is generally bad for a person.

LaCroix sympathizes with the challenges faced when it comes to the modification of sedentary behavior. Nevertheless, LaCroix knows that such modifications are necessary, explaining that sitting all the time is not what humans are meant to do.