Variety and Duration of Different Sedentary Behaviors,Inflammation, Genetic Susceptibility,and New-Onset Dementia in the Older Population

ObjectivesWe aimed to evaluate the relationship of the variety and duration of different sedentary behaviors (TV-watching, driving, and nonoccupational computer use) with the risk of dementia in older participants, and examine whether inflammation and genetic susceptibility may modify the relationship.DesignA prospective cohort study.Setting and Participants173,829 older participants (≥60 years) without prior dementia in the UK Biobank were enrolled.MethodsA healthy sedentary behavior score was calculated as the number of the 3 major sedentary behaviors with a duration associated with the lowest risk of dementia. The primary outcome was new-onset all-cause dementia.ResultsDuring a median follow-up of 12.4 years, 4965 (2.9%) participants developed new-onset dementia. There were U-shaped associations for TV-watching and driving time, and a reversed J-shaped association for nonoccupational computer use time with new-onset all-cause dementia, with the lowest dementia risk at >0-<2 hours/day for all the 3 sedentary behaviors. Moreover, a higher healthy sedentary behavior score was significantly associated with a lower risk of all-cause dementia (per 1 score increment: hazard ratio 0.78, 95% CI 0.75-0.81), with a stronger inverse association in those with higher levels of high-sensitivity C-reactive protein and monocytes (both P-interactions <.05). Genetic risks of dementia did not significantly modify the association. Similar trends were found for new-onset Alzheimer's disease and vascular dementia.Conclusions and ImplicationsThe associations between the duration of different sedentary behaviors and new-onset dementia were different in the older population. Moreover, the variety of sedentary behavior was inversely associated with new-onset dementia, especially among those with higher levels of inflammation.