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(HealthDay News) — For older adults, there is a significant association between more time spent in sedentary behavior and a higher incidence of all-cause dementia, according to a study published in the Sept. 12 issue of the Journal of the American Medical Association.

David A. Raichlen, Ph.D., from the University of Southern California in Los Angeles, and colleagues examined whether there is an association between accelerometer-assessed sedentary behavior and incident dementia in a retrospective study involving 49,841 adults aged 60 years or older who were followed for a mean of 6.72 years.

The researchers found that 414 individuals were diagnosed with incident all-cause dementia during follow-up. There was a significant nonlinear association between time spent in sedentary behavior and incident dementia in fully adjusted models. The hazard ratios for dementia were 1.08, 1.63, and 3.21 for 10, 12, and 15 hours per day, respectively, relative to a median of 9.27 hours/day. Per 1,000 person-years, the adjusted incidence rate of dementia was 7.49, 8.06, 12.00, and 22.74 for 9.27, 10, 12, and 15 hours/day, respectively.

Mean daily sedentary bout length and maximum daily sedentary bout length were significantly associated with a higher risk for incident dementia, but after adjustment for time spent in sedentary behavior, the associations were no longer significant. The number of sedentary bouts per day was not associated with the risk for incident dementia.

“More time spent in sedentary behaviors was significantly associated with higher incidence of all-cause dementia,” the authors write. “Future research is needed to determine whether the association between sedentary behavior and risk of dementia is causal.”

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