Cardiorespiratory fitness (CRF) is associated with reduced mortality and chronic disease risk, but its relationship with broader healthy aging outcomes remains less defined. A longitudinal cohort study published in the Journal of the American College of Cardiology evaluated associations between midlife CRF and subsequent health span, disease burden, and lifespan among adults who remained free of major chronic disease until 65 years. 

The analysis included 24,576 participants (25% women) from the Cooper Center Longitudinal Study (CCLS) between 1971 and 2017, linked to Medicare claims data from 1999 to 2019. CRF was quantified using maximal treadmill testing before 65 years of age. 

Outcomes included onset of 11 major chronic conditions identified via the Medicare Chronic Conditions Data Warehouse, analyzed as composite, grouped (cardiovascular [CV], cardiovascular-kidney-metabolic [CKM], and cancer), and individual conditions. Illness-death models estimated transitions between health, disease, and death across CRF categories (low, moderate, high).

Compared with low-fit individuals, high-fit men demonstrated a 2% (95% confidence interval [CI]: 1%–2%) longer health span, 9% (95% CI: 1%–17%) fewer chronic conditions, and a 3% (95% CI: 2%–4%) longer lifespan, with comparable patterns observed in women. 

Higher CRF was also associated with delayed onset of CV, CKM, and cancer conditions and fewer diseases within each category. On average, onset of chronic conditions occurred at least 1.5 years later in high-fit individuals. Findings were consistent across subgroups stratified by age, sex, smoking status, body mass index, and enrollment period.

Higher midlife CRF was associated with extended health span and reduced disease burden. Delayed disease onset and modest lifespan gains were observed across fitness levels.