Large amounts of sedentary time linked to higher risk of dementia in older adults

Researchers used machine learning to explore the links between sedentary behavior and dementia, finding that total time spent being sedentary matters for brain aging among older adults. Whether driving, sitting at a computer or watching television, being sedentary for more than 10 hours per day rapidly increased the risk of dementia according to the study published recently in the Journal of the American Medical Association (JAMA).  

By Alzheimer's Prevention Bulletin

According to a study published in JAMA last month, older adults who are sedentary for more than 10 hours a day are at increased risk for dementia.  The study used a large dataset collected from people in the United Kingdom to investigate the possible links between sedentary behaviors- like driving or sitting- and dementia risk among adults aged 60 and older.  The adults in the study wore a wrist device that measured movement 24 hours a day for a week.  It is important to note that the researchers were able to separate out time spent sleeping nightly from sedentary time. After an average of six years of follow-up, the researchers used hospital records and death registry data to determine dementia diagnoses.  

"The risk of dementia begins to rapidly increase after 10 hours spent sedentary each day," said study co-author Gene Alexander, PhD, a University of Arizona professor of psychology and psychiatry and a professor in the university's Evelyn F. McKnight Brain Institute and BIO5 Institute. "This suggests that it is the total time spent sedentary that drove the relationship between sedentary behavior and dementia risk. But, importantly, lower levels of sedentary behavior, up to around 10 hours, were not associated with increased risk." 

The findings are even more notable considering that the average American is sedentary for about 9.5 hours per day when they are awake. 

Do shorter durations of sedentary time help?
The study revealed that the way sedentary time was accumulated throughout the day does not matter; it’s the total sedentary time each day that impacts one’s dementia risk.  

"Many of us are familiar with the common advice to break up long periods of sitting by getting up every 30 minutes or so to stand or walk around," lead study author David Raichlen, PhD, professor of biological sciences and anthropology at University of Southern California said. "We wanted to see if those types of patterns are associated with dementia risk. We found that once you take into account the total time spent sedentary, the length of individual sedentary periods didn't really matter."

How can you reduce your dementia risk?
Dr. Alexander shared that “it’s never too late to start” being more active and provided the following advice for older adults:

1. Sit less and move more.
2. Engage in activities you enjoy.
3. Schedule time with friends or groups who also enjoy the same activities.
4. Align your activities with your abilities so you can avoid feeling frustrated or experiencing an injury.
5. Be mindful of how much total time you sit each day.

This study is part of a larger effort by the researchers to understand how sedentary behavior and physical activity affects brain health and risks of dementia. Stay tuned for future issues of the Alzheimer’s Prevention Bulletin for updates on this research.

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