The Intersection of Physical Inactivity, Dementia, and Gender: A Population-Based Study of All-Cause Mortality in Middle-Aged and Older Adults in Korea

Background and Objectives: Physical activity and dementia are important determinants of mortality in aging populations, yet their joint association remains insufficiently understood. This study examined the combined association of physical activity and dementia with all-cause mortality in a nationally representative cohort of Korean adults. Materials and Methods: We used data from the Korean Longitudinal Study of Aging (KLoSA), with baseline in 2018 and follow-up through 2022. A total of 6935 participants were included. Physical activity was categorized based on weekly exercise duration using World Health Organization recommendations (Inactive <150 min/week, and ≥150 min/week). Dementia was defined by self-reported physician diagnosis. Cox proportional hazards models were used to estimate hazard ratios (HRs) for mortality, adjusting for relevant covariates. Sex-stratified analyses were conducted as sensitivity analyses. Results: During follow-up, 597 deaths occurred. Participants with both dementia and inactivity had the highest mortality risk. Sufficient physical activity (≥150 min/week) was associated with lower mortality risk overall. In sex-stratified analyses, the protective association of sufficient physical activity appeared more evident among women; however, subgroup findings should be interpreted cautiously due to limited events. Conclusions: Physical inactivity and dementia were jointly associated with increased mortality risk. Maintaining adequate physical activity may be particularly important in cognitively vulnerable populations, although further research is needed to confirm subgroup-specific patterns.