Dose–response association between daily step count and health-related outcomes in older adults: a nationwide cross-sectional study in Thailand

BACKGROUND: Daily step count has emerged as a practical and objective metric of physical activity. However, evidence linking step volume to multidimensional health-related outcomes in Asian older adults remains limited. This study aimed to examine the dose-response associations between objectively measured daily step counts and quality of life, knee-specific functional outcomes, and physical performance in community-dwelling older adults, and to identify clinically meaningful step count thresholds. METHODS: This nationwide cross-sectional study included 2,603 Thai adults aged ≥ 60 years recruited using multi-stage probability sampling. Daily step counts were measured using wrist-worn accelerometers over 7 days and categorized into six groups (≤ 3,000 to > 15,000 steps/day). Outcomes included EuroQol 5-Dimension 5-Level (EQ-5D-5 L) utility, EuroQol Visual Analogue Scale (EQ-VAS), Knee Injury and Osteoarthritis Outcome Score (KOOS), Oxford Knee Score (OKS), Timed Up and Go test (TUG), Five Times Sit-to-Stand test (5×STS), gait speed, and leg strength. Multivariable linear regression models adjusted for age, sex, BMI, comorbidity, knee osteoarthritis, and geographic region were used to evaluate independent associations. RESULTS: The mean daily step count was 9,488 ± 5,639 steps per day. All eight outcomes demonstrated significant monotonic dose-response relationships across step count groups (p < 0.001 for trend). After full adjustment, the highest step count group (> 15,000 steps/day) had significantly better outcomes than the lowest (≤ 3,000 steps/day), including shorter TUG time (- 3.7 s), faster gait speed (+ 0.20 m/s), higher KOOS (+ 9.5 points), and higher EQ-5D-5 L utility (+ 0.087) (all p < 0.001), with several differences exceeding established minimal clinically important thresholds. Associations were most pronounced among participants aged > 75 years. CONCLUSIONS: Higher daily step counts are independently associated with better quality of life, knee-specific function, and physical performance among community-dwelling Thai older adults. A target of 6,000-9,000 steps per day appears clinically meaningful and pragmatically attainable. Daily step count may serve as a practical and scalable metric to guide healthy aging strategies in Asian populations.