Prediction of 30-Year Risk for Cardiovascular Mortality by Fitness and Risk Factor Levels
The Cooper Center Longitudinal Study
Background—Fitness and traditional risk factors have well-known associations with cardiovascular disease (CVD) death in both short-term (10 years) and across the remaining lifespan. However, currently available short-term and long-term risk prediction tools do not incorporate measured fitness.
Methods and Results—We included 16 533 participants from the Cooper Center Longitudinal Study (CCLS) without prior CVD. Fitness was measured using the Balke protocol. Sex-specific fitness levels were derived from the Balke treadmill times and categorized into low, intermediate, and high fit according to age- and sex-specific treadmill times. Sex-specific 30-year risk estimates for CVD death adjusted for competing risk of non-CVD death were estimated using the cause-specific hazards model and included age, body mass index, systolic blood pressure, fitness, diabetes mellitus, total cholesterol, and smoking. During a median follow-up period of 28 years, there were 1123 CVD deaths. The 30-year risk estimates for CVD mortality derived from the cause-specific hazards model demonstrated overall good calibration (Nam-D’Agostino χ2 [men, P=0.286; women, P=0.664] and discrimination (c statistic; men, 0.81 [0.80–0.82] and women, 0.86 [0.82–0.91]). Across all risk factor strata, the presence of low fitness was associated with a greater 30-year risk for CVD death.
Conclusions—Fitness represents an important additional covariate in 30-year risk prediction functions that may serve as a useful tool in clinical practice.
- Received June 19, 2013.
- Accepted April 28, 2014.
- © 2014 American Heart Association, Inc.