LOS ANGELES — People over 60 who frequently remain seated for hours at a time are at a heightened risk for dementia, according to a new study. Moreover, researchers from the University of Southern California say getting up to stretch regularly doesn’t erase the cumulative damage of a sedentary lifestyle.
Using data from the United Kingdom, USC researchers discovered that senior citizens who engage in above-average amounts of sedentary activities such as watching television or driving are more susceptible to this degenerative condition. The study highlights a marked increase in dementia risk among adults who sit for roughly 10 hours daily. The average American sits for 9.5 hours each day.
Interestingly, the research indicates that the main problem is the total amount of inactivity rather than how a person reaches this level of sedentary time.
“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. 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,” says study author David Raichlen, professor of biological sciences and anthropology at the USC Dornsife College of Letters, Arts and Sciences, in a university release.
For this research, the team pulled data from the UK Biobank database to explore potential links between sitting duration and dementia risk. Over 100,000 adults participated by wearing accelerometers, devices that measure movement, all day for one week. The study mainly centered on approximately 50,000 adults over 60 free of dementia at the beginning of the project.
Using a machine-learning algorithm, the researchers analyzed the vast set of accelerometer data, categorizing behavior based on varying physical activity intensities. This algorithm could differentiate activities, such as discerning sedentary behavior from sleeping. This accelerometer data, when combined with sophisticated computational techniques, granted the researchers insights into the durations of different sedentary behaviors.
After tracking these participants for an average of six years, the researchers referenced hospital records and death registries to identify dementia diagnoses, finding 414 cases. When analyzing the data, the team controlled for factors including age, sex, education, race, genetics, chronic conditions, and lifestyle habits (like exercise, diet, alcohol consumption, smoking, and self-reported mental health) which might influence brain health.
While extended sitting durations correlated with higher dementia risk, not all sedentary periods were detrimental.
“We were surprised to find that the risk of dementia begins to rapidly increase after 10 hours spent sedentary each day, regardless of how the sedentary time was accumulated. 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,” says 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,” Raichlen adds.
The study, published in JAMA, builds on previous research, which used self-reported health data to investigate how certain types of sedentary behavior – such as sitting and watching TV – affect dementia risk more than others.
“Our latest study is part of our larger effort to understand how sedentary behavior affects brain health from multiple perspectives. In this case, wearable accelerometers provide an objective view of how much time people dedicate to sedentary behavior that complements our past analyses,” Raichlen concludes.
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South West News Service writer Stephen Beech contributed to this report.
Dementia seems not to be strongly related to numbers of hours sitting but how active the brain is during those hours. Complex work contributes to brain function more than number of hours of physical activity.