The study, which involved 49,841 men and women ages 60 and older, “supports the idea that spending more time with sedentary behaviors increases the risk of dementia,” said Andrew Budson, a professor of neurology at Boston University and author from Seven Steps to Management. Your Aging Memory, who was not involved in the study.
The results also underline how widespread the consequences of sitting can be, affecting our minds as well as our bodies, and hint that exercise alone may not be enough to protect us.
The danger of sitting too long
The disadvantages of sitting too much are well known to scientists and most of the rest of us. Previous research shows that people who sit throughout the day, accumulating multiple hours of sedentary time in the office, on the go, and at home, in front of televisions and computers, are more likely to develop heart disease, obesity, diabetes and other diseases and die prematurely than people who often get up and move.
Sitting can even undermine exercise. According to other recent research, people who exercise but then sit the rest of the day end up erasing some of the expected metabolic benefits of their effort.
But it’s less clear whether sitting also affects brain health. Some studies have linked sitting to later memory problems, including Alzheimer’s disease and other forms of dementia. But they have mainly relied on people’s recollection of how long they sat, which can be quite inaccurate.
So for the new study, scientists at the University of Southern California in Los Angeles and other universities looked for objective measures of sitting and found them in the UK Biobank, a large repository of data on life, health and the death of hundreds of thousands. of British men and women.
Many of the Biobank participants wore a sophisticated activity tracker for a week after joining the study to carefully record their movements (and stillness) throughout the day.
The scientists obtained records from nearly 50,000 of these men and women aged 60 or older who did not have dementia when they joined the study.
With the help of artificial intelligence algorithms that could interpret the tracker’s readings, the scientists identified every minute during the day when people were on the move or were sedentary, that is, they were sitting or lying, but not sleeping.
Sitting for 10 hours increases brain risks
They then checked people’s medical status over the next seven years or so, looking for hospital or death records that detailed a diagnosis of dementia of any type.
Finally, they compared sitting habits and brain health. And they found strong correlations.
If men and women sat for at least 10 hours a day, which many of them did, their risk of developing dementia over the next seven years was 8 percent higher than if they sat for less than 10 hours.
The risks increased from there, reaching a 63 percent higher risk of dementia for people who spent at least 12 hours in a chair.
“Sitting in the office all day, then in front of the TV and in the car and all the other ways we find to sit, it adds up,” said David Raichlen, a professor of biological sciences and anthropology at the University of Southern California. , who led the new study. “These extreme levels of sedentary behavior are where we see a much higher risk” of cognitive and memory decline.
Exercise does not eliminate sitting
Surprisingly, the researchers They found few benefits from exercise.
People who exercised but then slumped in chairs for 10 hours or more were just as prone to dementia as people who hadn’t exercised much.
“It seems like you can’t avoid risk through exercise,” Raichlen said.
What about standing desks or walking breaks?
The same was true for walks and other short breaks. After adjusting for other factors, the researchers noticed little improvement among people who interrupted their sitting time with breaks. If they got up and walked, but still managed to sit for 10 hours or more a day, their risk didn’t change much. What ultimately mattered was how many hours, in total, a person spent in a chair most days.
However, some questions remain about standing and standing desks, in part because it’s not always easy to differentiate between sitting and standing in activity tracker data. Standing is not generally considered a sedentary behavior, but it is not clear in this study whether it can reduce the brain risks of sitting.
The best way to reduce your risk of dementia, Raichlen said, is to find ways to sit less overall. “People in our study who were sedentary for 9.5 hours a day did not have any increased risk,” she said.
If your job requires a lot of desk and computer time, look for opportunities during the day to be on the go. Walk around your office while talking on the phone. Schedule walking meetings. Pick up your lunch instead of having it delivered.
Try to keep track of how many hours you spend motionless. As you reach or exceed 10, Raichlen said, move more and zoom less.
Of course, this study was associative and cannot prove that sitting causes cognitive decline. It also doesn’t tell us how the two could be related.
“There have been suggestions that cerebral blood flow is affected” by sitting, Raichlen said, reducing the supply of oxygen and fuel to the brain. We may also snack poorly or eat poorly when we sit for hours, especially in front of the TV, which could influence long-term brain health.
However, the encouraging news about overwork is that it can be undone, Raichlen said. “Sit less, move more. “That’s the message and we probably can’t repeat it enough.”
Do you have any questions about fitness? Email TuMove@washpost.com And we may answer your question in a future column.