Physical Activity Intensity and Suspected Dementia in Older Japanese Adults: A Dose-Response Analysis Based on an 8-Year Longitudinal Study.

Abstract

Moderate- to vigorous-intensity physical activity (PA) may reduce the risk of dementia; however, few studies have examined the effects of PA intensity on dementia risk. To prospectively examine the dose-response relationship of PA intensity with the incidence of suspected dementia in community-dwelling older adults. We conducted a baseline mail survey with an 8-year follow-up of 3,722 older adults in Japan. We assessed PA levels using the International Physical Activity Questionnaire short form and calculated the amount of time per week spent performing moderate- and vigorous-intensity PA (VPA). Information regarding suspected dementia was obtained from the city database during the follow-up period. Cox proportional-hazard models with age as time scale, and delayed entry and restricted cubic spline regression as variables were used to estimate risk of developing suspected dementia, excluding cases occurring < 1 year after baseline evaluation. The cumulative incidence of suspected dementia during the follow-up period was 12.7%. Compared with those who did not practice moderate-intensity PA (MPA), those who practiced≥300 min (hazard ratio, 0.73; 95% confidence interval 0.56-0.95) of MPA showed a lower risk of developing suspected dementia. Furthermore, when the dose-response relationship was examined, the hazard of developing suspected dementia decreased almost linearly with MPA. A significantly lower hazard was observed from 815 minutes/week. There was no significant association between VPA and suspected dementia. This study suggested that MPA is often practiced in older adults and this PA intensity has a sufficiently favorable effect on dementia prevention.