P2-149: physical exercise in mid-life versus late life may have a differential impact on the outcome of incident mild cognitive impairment: the mayo clinic study of aging

Physical exercise is associated with possible benefits for neurocognitive health. However, there is a lack of prospective cohort studies that examined the association between timing of engagement in physical exercise in cognitively normal persons and the outcome of incident mild cognitive impairment (MCI) in late life. We conducted a prospective cohort study derived from the population-based Mayo Clinic Study of Aging. The participants were 1,830 cognitively normal persons at baseline. They underwent neurological evaluation, risk factors ascertainment, and neuropsychological testing. Additionally, physical exercise in mid-life and late life were measured by using a validated survey with ordinal responses. An expert consensus panel classified participants as being cognitively normal or having new onset MCI after reviewing neurological, cognitive, and other pertinent data and according to published criteria. We calculated hazard ratios (HR) and 95% confidence intervals (95% CI) using Cox proportional hazards model, after adjusting for age, sex, and education. The cohort was followed forward in time for a median of 3.2 years to the outcomes of incident MCI or censoring variables. Of 1,830 cognitively normal persons at baseline, 389 developed incident MCI at follow-up. Light (HR = 0.58; 95% CI, 0.43-0.79) as well as vigorous (HR = 0.78; 95% CI, 0.63-0.97) mid-life physical exercise were associated with decreased risk of incident MCI. However, the association with moderate mid-life physical exercise (HR = 0.85; 95% CI, 0.67-1.09) was marginally significant. With regard to physical exercise in late life, we observed that light (HR = 0.75; 95% CI, 0.58-0.97) and moderate (HR = 0.81; 95% CI, 0.66-0.99) but not vigorous (HR = 0.90; 95% CI, 0.66-1.25) physical exercise were associated with decreased risk of incident MCI. Light physical exercise in mid-life and late life were associated with decreased risk of incident MCI. Additionally, vigorous mid-life as well as moderate late life physical exercise were associated with decreased risk of incident MCI. These findings indicate that (1) most elderly individuals may not engage in vigorous physical exercise in late life and that (2) the intensity of physical exercise in mid-life versus late life may have a differential impact on the outcome of incident MCI.