Sedentary behavior has been related to a number of health problems, including an increased risk of dementia in the elderly. Several studies have revealed a link between a sedentary lifestyle and cognitive deterioration in older persons, including an increased risk of dementia and Alzheimer’s disease. Researchers employed machine learning to investigate the relationships between sedentary behavior and dementia, discovering that total sedentary time matters for brain aging.
According to a new study by USC and University of Arizona researchers, adults aged 60 and older who spend more time participating in sedentary habits such as sitting while watching TV or driving may be at increased risk of acquiring dementia. Their study found that persons who spend more than 10 hours a day participating in sedentary habits like sitting are at a higher risk of dementia, which is a noteworthy result given that the average American sits for roughly 9.5 hours each day.
The study, published in JAMA, also found that the pattern of sedentary activity throughout the course of the day did not contribute as much as the total amount of time spent sedentary each day. According to research author David Raichlen, total sedentary activity exhibited a similar link with dementia whether spent in long periods spanning several hours or spread out irregularly throughout the day.
Our latest research is part of a larger effort to understand how sedentary behavior affects brain health from a variety of perspectives. In this case, wearable accelerometers provide an objective view of how much time people spend in sedentary behavior, which complements our previous analyses.
David Raichlen
“Many of us are familiar with the popular advice to break up extended periods of sitting by standing or walking around every 30 minutes or so. We wanted to explore if these patterns are linked to dementia risk. “We discovered that once you account for total sedentary time, the length of individual sedentary periods didn’t really matter,” said Raichlen, a professor of biological sciences and anthropology at the University of Southern California’s Dornsife College of Letters, Arts, and Sciences.
Researchers examined probable correlations between sedentary behavior and dementia risk using data from the U.K. Biobank, a large-scale biological database of volunteers from across the United Kingdom.
Over 100,000 participants agreed to wear accelerometers, wrist-worn devices that measure movement, for 24 hours per day for one week as part of a U.K. Biobank sub-study. The researchers focused on a sample of around 50,000 persons over the age of 60 who did not have a dementia diagnosis at the start of the trial.
The researchers then used a machine-learning technique to assess the vast dataset of accelerometer measurements and classify activities based on physical activity intensity. The system was able to distinguish between different types of activity, such as inactive versus sleeping behavior. Researchers were able to obtain an objective estimate of the time spent engaged in various forms of sedentary behaviors by combining accelerometer data with modern computational techniques.
After an average of six years of follow-up, the researchers used inpatient hospital records and death registry data to determine dementia diagnosis. They found 414 cases positive for dementia. Then, the team adjusted their statistical analysis for certain demographics (e.g., age, sex, education level, race/ethnicity, chronic conditions, genetics) and lifestyle characteristics (physical activity, diet, smoking and alcohol use, self-reported mental health) that could affect brain health.
Total time spent sedentary each day drives dementia risk
While excessive sedentary behavior was connected with an increased risk of dementia, the researchers discovered that specific levels of sedentary behavior were not associated with dementia.
“We were surprised to discover that the risk of dementia increases rapidly after 10 hours of sedentary time per day, regardless of how the sedentary time was accumulated.” This suggests that the total amount of sedentary time is what drives the relationship between sedentary behavior and dementia risk, but lower levels of sedentary behavior, up to around 10 hours, were not associated with increased risk,” said study author Gene Alexander, professor of psychology and psychiatry at the Evelyn F. McKnight Brain Institute at the University of Arizona and Arizona Alzheimer’s Disease Research Center.
“This should provide some reassurance to those of us with office jobs that involve prolonged periods of sitting, as long we limit our total daily time spent sedentary,” said Raichlen.
The study expands on their prior research, which used self-reported health data to analyze how some types of sedentary activity, such as sitting and watching TV, are more likely to increase dementia risk than others.
“Our latest research is part of a larger effort to understand how sedentary behavior affects brain health from a variety of perspectives. In this case, wearable accelerometers provide an objective view of how much time people spend sedentary behavior, which complements our previous analyses,” Raichlen explained. More research is needed to determine causality and whether physical activity can reduce the chance of getting dementia, according to scientists.
