Percentage of Age-Predicted Cardiorespiratory Fitness Is Inversely Associated with Cardiovascular Disease Mortality: A Prospective Cohort Study

Abstract

Introduction: Percentage of age-predicted cardiorespiratory fitness (% age-predicted CRF) is a potentially useful cardiopulmonary exercise testing (CPX) parameter, but there are limited data on its prognostic relevance for adverse cardiovascular disease (CVD) outcomes. We aimed to assess the association of % age-predicted CRF with CVD mortality and the extent to which % age-predicted CRF measurements could improve the prediction of CVD mortality. Methods: Peak oxygen uptake, used as the measure of CRF, was directly assessed in 2,276 men who underwent CPX. The age-predicted CRF estimated from a regression equation for age was transformed to % age-predicted CRF with the following formula: (achieved CRF/age-predicted CRF) × 100. Hazard ratios (HRs) (95% confidence intervals [CIs]) and measures of risk discrimination for CVD mortality were calculated. Results: During a median follow-up of 28.5 years, 643 fatal CVDs were recorded. The relationship between % age-predicted CRF and CVD mortality was dose response in nature. In analysis adjusted for conventional risk factors, one standard deviation increase in % age-predicted CRF was associated with a reduced risk of CVD mortality (HR 0.61; 95% CI: 0.56–0.67), which was minimally attenuated on further adjustment for several other confounders (HR 0.71; 95% CI: 0.64–0.78). Addition of % age-predicted CRF to a CVD mortality risk prediction model containing established risk factors significantly improved risk discrimination and reclassification. Conclusion: Percentage of age-predicted CRF is inversely and independently associated with CVD mortality in a graded fashion and significantly improves the prediction and classification of the long-term risk for CVD mortality beyond established risk factors.