Joint Effect of Subjective Memory Impairment and Physical Inactivity on Cognitive Impairment: A 2-Year Follow-Up Study Among the Elderly in a Korean Population-Based Cohort Study.

AIM: Subjective memory impairment and insufficient physical activity (IPA) are individual risk factors for dementia. This study investigated the interactive effects of severe subjective memory impairment (SSMI) and IPA on cognitive impairment in older adults in a Korean population-based cohort. METHODS: This prospective cohort study included 703 community-dwelling adults aged ≥ 60 years. Cognitive impairment was assessed using the Mini Mental Status Examination for Dementia Screening. The SSMI was assessed using the Subjective Memory Complaints Questionnaire-Global and IPA was examined using the Swedish Mammography Cohort Physical Activity Questionnaire. We calculated the Relative Excess Risk due to Interaction (RERI) to estimate the magnitude of the additive interaction. We also estimated the attributable proportion (AP), which estimates the amount of overall risk that can be explained by the variable. RESULTS: We categorized into four groups based on the presence or absence of SSMI and IPA: S-I- (no SSMI, no IPA), S-I+ (no SSMI, with IPA), S+I- (with SSMI, no IPA), and S+I+ (with SSMI, with IPA). At the 2-year follow-up, the excess risk of cognitive impairment due to the interaction between SSMI and IPA was 123% (RERI), representing 38% (AP) of the total risk (RERI = 1.23, 95% CI: 0.07-4.72; AP = 0.38, 95% CI: 0.07-0.69). CONCLUSION: The interaction effect of SSMI and IPA was greater than the individual effects of each factor in cognitive impairment. These findings suggest the importance of targeting older adults with both SSMI and IPA for effective dementia prevention strategies.