Questionnaire-derived physical activity, sleep, and cognition in older adults with and without subjective memory decline

Subjective memory decline (SMD) is a risk marker for later cognitive impairment. Physical activity is a modifiable lifestyle factor, but its associations with sleep, physical function, and cognition in community-dwelling older adults with and without SMD remain unclear. This short-term longitudinal study included 208 adults aged ≥ 60 years from the Inner Mongolia Elderly Health Comprehensive Assessment. Baseline habitual physical activity was assessed using a study-specific, interviewer-administered questionnaire covering activity frequency, duration, and intensity during a typical week in the preceding month. Moderate-to-vigorous physical activity (MVPA) and sedentary time were derived from questionnaire responses. Global cognitive function was assessed using the Montreal Cognitive Assessment (MoCA) at baseline and follow-up. Associations were examined using hierarchical multivariable linear regression and linear mixed-effects models. Exploratory mediation analyses assessed sleep quality and physical performance. Higher baseline MVPA was independently associated with better MoCA performance after full adjustment (β = 0.15 MoCA points per 1000 MET-min/week; 95% CI: 0.03–0.27; P = 0.012). Exploratory analyses of MoCA subdomain scores (executive function, attention, memory, language, and visuospatial function) showed the strongest associations with executive function and attention; these two associations remained significant after false-discovery-rate correction. Over follow-up of up to 6 months (median, 3.2 months), higher baseline MVPA was associated with a smaller short-term monthly decrease in MoCA (Time × MVPA interaction: β = 0.004 MoCA points/month per 1000 MET-min/week; P = 0.026). Sleep quality and physical performance partly explained the cross-sectional MVPA-cognition association in exploratory analyses. Similar association patterns were observed by SMD status, although subgroup findings should be interpreted cautiously. Questionnaire-derived MVPA was associated with better baseline cognition and a modestly smaller short-term decrease in repeated MoCA scores in older adults with and without SMD. The short observation window does not support inference about long-term cognitive protection. Longer studies using objective activity monitoring are warranted.