Self-reported cardiorespiratory fitness: prediction and classification of risk of cardiovascular disease mortality and longevity--a prospective investigation in the Copenhagen City Heart Study

Abstract

Background: The predictive value and improved risk classification of self-reported cardiorespiratory fitness (SRCF), when added to traditional risk factors on cardiovascular disease (CVD) and longevity, are unknown.

Methods and results: A total of 3843 males and 5093 females from the Copenhagen City Heart Study without CVD in 1991-1994 were analyzed using multivariate Cox hazards regression to assess the predictive value and survival benefit for CVD and all-cause mortality from SRCF. The category-free net reclassification improvement from SRCF was calculated at 15-year follow-up on CVD and all-cause mortality. Overall, 1693 individuals died from CVD. In the fully adjusted Cox model, those reporting the same (hazard ratio [HR], 1.17; 95% confidence interval [CI], 1.04 to 1.32) and lower (HR, 1.91; 95% CI, 1.62 to 2.24) SRCF than peers had an increased risk of CVD mortality, compared with individuals with higher SRCF. Compared with individuals with higher SRCF, those with the same and lower SRCF had 1.8 (95% CI, 1.0 to 2.5) and 5.1 (95% CI, 4.1 to 6.2) years lower life expectancy, respectively. Individuals with lower SRCF had a significantly increased risk of CVD mortality, compared with individuals with higher SRCF, within each strata of leisure time physical activity and self-rated health, and SRCF significantly predicted CVD mortality independently of self-rated health and walking pace. A net reclassification improvement of 30.5% (95% CI, 22.1% to 38.9%) for CVD mortality was found when adding SRCF to traditional risk factors. Comparable findings were found for all-cause mortality.

Conclusions: SRCF has independent predictive value, is related to a considerable survival benefit, and improves risk classification when added to traditional risk factors of CVD and all-cause mortality. SRCF might prove useful in improved risk stratification in primary prevention.

Keywords: cardiovascular mortality; net reclassification improvement; self‐reported fitness.

© 2015 The Authors. Published on behalf of the American Heart Association, Inc., by Wiley Blackwell.

Figures

Figure 1.

Self‐reported cardiorespiratory fitness (Cox regression HRs with 95% CIs) from 1991 to 1994 as predictor of cardiovascular disease mortality and all‐cause mortality with median follow‐up of 17.9 years among males and females without a history of cardiovascular disorders in the Copenhagen City Heart Study (n=8936). Survival benefits were calculated by integrating the Cox regression model‐adjusted mean survival Makuch‐Ghali curves for each of the groups “higher than peers,” “same as peers,” and “lower than peers” self‐reported cardiorespiratory fitness. *P<0.05; **P<0.01; ***P<0.001. BMI indicates body mass index; BP, blood pressure; CI, confidence interval; HR, hazard ratio.