Changes in physical fitness and all-cause mortality. A prospective study of healthy and unhealthy men.
Level 3 - non-randomized controlled study
Prospective observational cohort study tracking fitness changes across two time points and subsequent mortality
What was done
A prospective cohort study evaluated 9,777 men attending a preventive medicine clinic who completed two clinical evaluations (mean interval: 4.9 years). Cardiorespiratory fitness was objectively measured at both examinations using maximal exercise treadmill tests alongside health status assessments. Participants were followed for an average of 5.1 years after the second examination to assess all-cause mortality (n = 223) and cardiovascular disease mortality (n = 87).
What was found
Age-adjusted all-cause mortality rates per 10,000 man-years were: - Unfit at both examinations: 122.0 - Improved from unfit to fit: 67.7 - Fit at both examinations: 39.6 Men who improved from unfit to fit achieved a 44% reduction in mortality risk (95% CI, 25% to 59%) compared with men who remained persistently unfit, an association that persisted after adjusting for age, baseline health status, and other risk factors. Each 1-minute increase in maximal treadmill time between examinations was associated with a 7.9% reduction in mortality risk (P = .001). Similar patterns were observed for cardiovascular disease mortality and when stratified by baseline health status.
Why it matters
This study provides evidence that cardiorespiratory fitness is a modifiable risk factor, demonstrating that improving fitness in adulthood confers substantial survival benefits rather than fitness being solely a fixed genetic trait.
Limits
The study was conducted exclusively in men attending a single preventive medicine clinic, limiting generalizability to women and broader socioeconomic populations. As an observational study, residual confounding and reverse causation cannot be fully ruled out despite statistical adjustments. Total event counts were modest (223 all-cause and 87 cardiovascular deaths).
Cited by
- context Research by Jonathan Myers and the Cooper Clinic shows that individuals who improve their fitness over time gain a survival advantage equivalent to those who maintained high fitness, whereas those who lose fitness lose that advantage.