10-plus hours of sedentary time linked to increased dementia risk

(NewsNation) — Adults aged 60 and older who spend more time being sedentary could be at a higher risk of developing dementia, a new study found.

Researchers at the University of Southern California and the University of Arizona wrote in a study published Tuesday in the Journal of the American Medical Association that dementia risk significantly increased among adults spending over 10 hours a day on sedentary behaviors like sitting or watching TV.

However, lower levels of sedentary behavior were not associated with this increased risk, the study said.

“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,” study author David Raichlen, a professor of biological sciences and anthropology at the University of Southern California, said in a statement.

To determine this, researchers used data from U.K. Biobank, a large-scale biomedical database of genetic and health information from 500,000 participants in the United Kingdom.

Over 100,000 adults agreed to wear accelerometers, which are worn on the wrist to measure movement, for 24 hours per day for one week as part of a U.K. Biobank substudy.

Researchers focused on a group of older adults from the substudy who did not initially have a dementia diagnosis. Using a machine-learning algorithm, they were able to discern whether participants were truly taking part in sedentary behavior or sleeping, giving researchers an objective measure of how people spent their time. Those on the research team also adjusted statistical analysis for demographics, including race and ethnicity, chronic conditions and genetics as well as physical characteristics including diet, smoking and alcohol use and self-reported mental health, which could affect the brain.

In total, 49,841 adults older than 60 were followed by researchers for around six years on average. During this time, 414 of them were diagnosed with “incident all-cause dementia,” according to inpatient hospital records and death registry data.

“In the fully adjusted models, there was a significant nonlinear association between time spent in sedentary behavior and incident dementia,” the study said.

The study notes that it doesn’t matter whether the larger amounts of sedentary time spanned several hours or was spread out intermittently throughout the day — it still had adverse effects.

“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,” Raichlen said.

More research is necessary to determine whether the link between sedentary behavior and dementia risk is causal, the study says.