Simple tests of balance, strength, mobility, and endurance may offer clinicians an objective window into physiological reserve and help identify older adults at greater risk of death.
Study: Physical Fitness and All-Cause Mortality in Older Adults. Image Credit: Dusan Petkovic / Shutterstock
A recent JAMA Network Open study examined how objectively measured physical fitness relates to all-cause mortality in older adults.
Functional Capacity as an Indicator of Mortality Risk
Regular physical activity is fundamental to healthy aging, lowering the risk of cardiovascular disease, functional decline, and premature mortality. Despite this, current strategies for clinical risk stratification in older adults remain limited. Prognostic models that focus on comorbidities and disease-specific factors often fail to adequately assess risk in the broader older population, especially those in early or preclinical stages of decline.
Epidemiologic studies typically rely on self-reported physical activity, which is susceptible to recall bias and inaccuracies. While some research has examined a variety of activity types, these complex profiles are not easily translated into clinical practice, where practical, objective, and reproducible risk indicators are essential.
Objective physical fitness assessments offer a complementary approach, reflecting cumulative physiological adaptation to activity, illness, and aging. Performance-based measures, such as cardiorespiratory fitness, muscular strength, balance, and mobility, are associated with mortality and major clinical outcomes, even after accounting for self-reported activity. These assessments provide a direct evaluation of physiological reserve, potentially supporting more refined risk stratification. However, evidence is limited regarding whether these associations are consistent across different fitness domains, sexes, and non-Western populations.
Although functional assessments complement established models of frailty and sarcopenia, they represent a broader, continuous measure of functional capacity. Few studies have evaluated multiple fitness domains or composite indices within the same older cohort, and clinically actionable dose-response relationships remain poorly defined. Addressing these gaps requires comprehensive research to clarify the potential of multidomain physical fitness assessment to refine risk stratification across diverse aging populations.
Objective Fitness Assessment for Enhanced Risk Stratification in Older Adults
The current study obtained relevant data from Taiwan’s National Physical Fitness Survey Database (NPFSD) and the National Health Insurance Research Database (NHIRD), linked via encrypted identifiers in accordance with national deidentification standards. 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. The analytic cohort excluded adults older than 90 years and individuals with multiple conditions likely to substantially limit fitness performance or with serious illnesses covered by Taiwan's Catastrophic Illness Certificate.
Physical fitness was assessed using standardized protocols across four domains: cardiorespiratory fitness (2-minute step test), muscular fitness (30-second arm curl and chair stand tests), flexibility (back scratch and chair sit-and-reach tests), and balance/agility (1-leg stance and 8-foot up-and-go tests).
Outcomes focused on all-cause mortality through December 31, 2022, were identified from the NHIRD death registry. Covariates included demographic, socioeconomic, geographic, and health-related factors from both databases.
Fitness measures were categorized into sex-specific quintiles (Q1: lowest performance [reference]; Q5: highest), and associations with mortality were examined using age-adjusted and multivariable Cox proportional hazards models, as well as restricted cubic spline analyses to assess dose-response relationships.
Higher Fitness Levels Associated With Greater Survival
Among 13,423 participants followed for a median of 7 years, the majority were women (62.5%) with a median age of 72. Approximately one-third reported regular physical activity, and the median body mass index (BMI) was 24.6. Hypertension, hyperlipidemia, diabetes, coronary heart disease, and chronic kidney disease were the most prevalent comorbidities.
Participants who died during follow-up were more often male, older, less physically active, socioeconomically disadvantaged, living alone, residing in less urbanized areas, and had a greater burden of comorbidities than survivors.
Survivors consistently outperformed those who died on all seven physical fitness assessments. Men generally scored higher on cardiorespiratory fitness, lower-body strength, and balance and agility, while women demonstrated greater flexibility.
Cumulative mortality rose steadily as fitness declined across all assessments. The composite fitness index showed the most pronounced separation in mortality across fitness levels, with the lowest performers facing the highest mortality. Across all fitness measures, higher physical fitness was consistently associated with reduced all-cause mortality hazard.
The composite fitness index showed the steepest mortality gradient; those in the highest fitness group had an adjusted mortality hazard about 61% lower than those in the lowest group. Balance, agility, lower-body strength, and cardiorespiratory fitness showed the strongest inverse associations with mortality, while upper-body strength and flexibility were less strongly linked to survival.
Sex-specific analyses showed that balance and agility had the strongest associations with lower mortality in men, followed by cardiorespiratory fitness, whereas lower-body strength, balance, and agility showed similarly strong associations in women. Cardiorespiratory fitness was also consistently associated with lower mortality in both sexes. Dose-response analyses further suggested that, for several fitness measures, differences in mortality were greatest at poorer performance levels, with associations tending to plateau as performance improved. Most of the mortality difference in the composite index was concentrated between the lowest-performing group and the higher-fitness groups.
Clinical Implications of Physical Fitness
Higher physical fitness in older adults is strongly associated with lower all-cause mortality. Regular assessment of fitness, including balance, strength, and endurance, may help identify individuals at higher risk and inform more targeted health interventions. By making fitness evaluation a routine part of care, clinicians may gain additional information about functional reserve beyond that provided by conventional disease-based assessments.
However, the findings do not establish that improving fitness itself reduces mortality. The observational design leaves the possibility of residual confounding and reverse causation; fitness was measured only once; smoking status was unavailable; and participants who completed the tests may have been healthier and more mobile than the broader older population. The study also did not formally test whether fitness measures improve prognostic accuracy over existing risk models.
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