Excessive Sitting for Over 10 Hours Daily May Heighten Dementia Risk

Older adults may have a new reason to get off the couch: a recent study suggests that having a sedentary lifestyle may increase the chances of developing dementia. 

Research published earlier this week in JAMA found that being sedentary for 10 hours or more each day was “significantly associated”with dementia, a general term for a loss of cognitive functioning. Symptoms include memory loss, confusion, and difficulty expressing thoughts.

'One of the most compelling things I find about the study is that regarding the associated risk with dementia, the total time spent being sedentary matters more than the way this time is being accumulated,' study author Daniel Aslan MS, a PhD candidate in human and evolutionary biology at the University of Southern California's Department of Biological Sciences, told Health. 

This new study is the largest to date to suggest that a sedentary lifestyle is a risk factor for dementia, Paul E. Schulz, MD, professor of neurology and director of the Neurocognitive Disorders Center at UTHealth Houston, told Health.

Research has also shown prolonged sitting can contribute to the development of cancer, back pain, and many other health issues.

To analyze the link between a sedentary lifestyle and dementia, the researchers turned to the UK Biobank, a medical data repository on half a million people living in the United Kingdom. 

The database had information on nearly 50,000 people aged 60 or older who wore accelerometers, which are wrist devices that track movement, continuously for one week sometime between 2013 to 2015. None of the people had dementia when they began wearing the accelerometer.

Researchers for the new study used medical records to determine that, about six years after people participated in the week-long experiments, 414 of them had developed dementia.

After analyzing the accelerometer data, they found that a participant's risk of developing dementia increased if they spent about 10 waking hours a day sedentary, meaning they were sitting or reclining and expending little energy (riding a bike, for example, would not have been considered sedentary, according to Aslan).

The risk shot up from there, with participants who were sedentary for 15 waking hours having triple the chance as their non-sedentary counterparts of developing dementia.

“The number of sedentary bouts per day was not associated with higher risk of incident dementia,” the researchers wrote. Instead, the total number of sedentary hours was what mattered.

“This is a very important study, “ said Schultz. “Instead of relying on subjective feelings about exercise, they used objective wrist detectors. And there was five to eight years of follow up, which in the over 60 age group is typically enough to pick up differences in dementia risk between groups.”

Jessica Caldwell, PhD, director of The Women's Alzheimer's Movement Prevention Center at Cleveland Clinic, also noted the study’s significance. “This study is a great example of using technology and complex analyses to understand how our behavior impacts our dementia risk,” she said. “It is particularly impressive because the study includes almost 50,000 people who wore activity tracking devices.”

However, she pointed out that the study didn’t analyze sedentary behavior in younger people, so it’s still unclear whether something like a career-long desk job might impact future dementia risk. 

The study does not show that sitting for long periods can cause dementia, according to the authors, just that being sedentary is associated with dementia risk. But Keiland Cooper, a doctoral researcher in cognitive science and neuroscience at the University of California, Irvine, told Health that scientists have some idea of how being sedentary may contribute to dementia symptoms. 

“While not fully understood, reduced physical activity leads to a range of negative effects, including weight gain, increased inflammation, and reduced blood flow to the brain,” she said. “Combined, these factors may increase a person’s dementia risk, most likely due to direct and indirect damage to brain cells.” 

Schultz said that dementia specialists believe lifestyle changes can reduce the risk of developing symptoms by as much as 50%—which seems like a compelling reason to get moving.

Experts said there are a few ways to incorporate movement into your day and—most importantly—stick to the habit. (“Healthy routines are like muscles; you build them by exercising them daily,” Carolyn Fredericks, MD, assistant professor of neurology at Yale School of Medicine, told Health.)

One way to stay active is to find something you enjoy, experts said, whether that's taking a dancing class or walking in the neighborhood. 

You can also pair an exercise that feels like a chore with something you do like to do, said Caldwell. That could mean watching a favorite program while riding a stationary bike, for example, or listening to a podcast while you walk. 

She said that having an exercise partner can also boost motivation and help hold you accountable. Even if you can't find a steady jogging or gym partner, having routine check-ins with a friend about fitness goals can accomplish the same purpose, she added.

And, suggested Schulz, it helps to get your spouse or partner on board. “If the spouse decides that they need to help their loved one by both of them exercising, then our patients, I find, are much more likely to engage in regular exercise,” he said.

While the study suggests that just being non-sedentary for fewer than 10 hours a day can benefit brain health, Fredericks said that 30 minutes of that non-sedentary time should be devoted to moderate-intensity cardio, such as jogging or swimming. 

“If you are already getting enough aerobic exercise, strength training, flexibility, and balance exercises are also key for both brain health and preventing injury,” Caldwell added.

If you have limited mobility, Aslan pointed out other strategies for keeping your brain sharp. 'People may be able to find other ways to reduce their risk of dementia, like engaging in more cognitively active tasks while being sedentary, such as solving puzzles, reading, or using a computer,' he said.