Accelerometer-measured multidimensional physical activity patterns and physical functional decline: a prospective national cohort study of aging

BACKGROUND: Physical activity (PA) is crucial for maintaining physical function in older adults, but relationships between multidimensional PA patterns and functional decline remain unclear. This study examined associations between accelerometer-measured PA patterns and physical function decline in older adults. METHODS: We conducted a prospective cohort study with 1-year follow-up using data from 586 community-dwelling participants aged ≥65 years in the National Health and Aging Trends Study (2021-2022). Wrist-worn accelerometers measured 4 PA dimensions: cumulative (total activity counts), peak (maximum intensity), temporal (active and sedentary minutes), and fragmentation. Physical function decline was defined as any decrease in Short Physical Performance Battery score at follow-up. Multivariable logistic regression examined associations between PA dimensions and physical function changes. RESULTS: Higher total activity counts (odds ratio [OR]: 0.71, 95% CI; 0.59-0.85), minutes spent active (OR: 0.75, 95% CI; 0.63-0.89), and maximum intensity (OR: 0.67, 95% CI; 0.55-0.83) were associated with lower odds of functional decline, while activity fragmentation showed the opposite relationship (OR: 1.23, 95% CI; 1.03-1.47). Dose-response analyses demonstrated continuous linear relationships. Compared to the lowest activity levels (10th percentile), participants at the 90th percentile showed substantially lower risk: total activity counts (OR: 0.50, 95% CI; 0.29-0.88), active minutes (OR: 0.58, 95% CI; 0.37-0.95), and maximum intensity (OR: 0.54, 95% CI; 0.32-0.75), while activity fragmentation showed progressive risk increase (OR: 1.37, 95% CI; 0.83-2.21). Domain-specific analyses showed consistent patterns. CONCLUSIONS: Multidimensional PA patterns have distinct relationships with functional decline in older adults. Findings support tailored PA recommendations and potential for targeted interventions.