Physical Fitness and All-Cause Mortality in Older Adults.

Importance: Regular physical activity promotes healthy aging, yet clinical risk stratification in older adults relies largely on comorbidity burden, often overlooking functional capacity. Objective fitness assessment may serve as a clinically relevant indicator of physiological reserve, but evidence from large cohorts evaluating multiple fitness domains remains limited. Objective: To evaluate associations between objectively measured physical fitness across multiple domains and all-cause mortality in older adults. Design, Setting, and Participants: This nationwide cohort study included community-dwelling adults aged 65 years or older who completed standardized fitness assessments in Taiwan between January 11, 2015, and November 25, 2016. Participant data were linked to National Health Insurance records, with follow-up through December 31, 2022. Statistical analyses were conducted between July 1, 2025, and May 30, 2026. Exposures: Physical fitness was assessed across 4 domains: cardiorespiratory fitness (2-minute step test), muscular strength (30-second arm curl and chair stand tests), flexibility (back scratch and chair sit-and-reach tests), and balance and agility (1-leg stance and 8-foot up-and-go tests). A composite fitness index was constructed by summing sex-specific percentile ranks across all 7 assessments. Main Outcome and Measures: The main outcome was all-cause mortality, ascertained through linkage with the National Health Insurance death registry. Multivariable Cox proportional hazards models estimated adjusted hazard ratios (AHRs), adjusting for sociodemographic factors, comorbidities, and self-reported physical activity. Results: Of 13 423 participants (mean [SD] age, 72.9 [6.1] years; 8394 female [62.5%]), 1631 (12.2%) died during a median (IQR) follow-up of 7.0 (6.7-7.1) years. Compared with the lowest performance quintile, participants in the highest performance quintile had lower all-cause mortality across 4 physical fitness assessments: 8-foot up-and-go (AHR, 0.41 [95% CI, 0.33-0.51]), 1-leg stance (AHR, 0.50 [95% CI, 0.42-0.59]), 30-second chair stand (AHR, 0.55 [95% CI, 0.46-0.65]), and 2-minute step test (AHR, 0.58 [95% CI, 0.49-0.68]). The composite fitness index showed the lowest risk of all-cause mortality (AHR, 0.39 [95% CI, 0.32-0.48]). Conclusions and Relevance: In this cohort study of older adults, objectively measured physical fitness-particularly balance and agility, lower-body strength, and cardiorespiratory fitness-was associated with lower all-cause mortality in a graded manner. These findings suggest that integrating objective fitness assessments into routine practice may refine risk stratification and guide function-oriented interventions in older adults.