Association of Cardiorespiratory Fitness With Coronary Heart Disease in Asymptomatic Men

Abstract

Objective: To examine the association of cardiorespiratory fitness (CRF) with risk of coronary heart disease (CHD) while controlling for an individual's Framingham Risk Score (FRS)-predicted CHD risk.

Patients and methods: The study included 29,854 men from the Aerobics Center Longitudinal Study, who received a baseline examination from January 1, 1979, to December 31, 2002. Coronary heart disease events included self-reported myocardial infarction or revascularization or CHD death. Multivariable survival analysis investigated the association between CRF, FRS, and CHD. Cardiorespiratory fitness was analyzed as both a continuous and a categorical variable. The population was stratified by "low" and "moderate or high" risk of CHD to test for differences in the FRS stratified by CRF.

Results: Compared with men without incident CHD, men with incident CHD were older (mean age, 51.6 years vs 44.6 years), had lower average maximally achieved fitness (10.9 metabolic equivalent of tasks vs 12.0 metabolic equivalent of tasks [METs]), and were more likely to have moderate or high 10-year CHD risk (P<.001). Cardiorespiratory fitness, defined as maximal METs, exhibited a 20% lower risk of CHD (hazard ratio, 0.80; 95% CI, 0.77-0.83) for each 1-unit MET increase. Among men in the low CRF strata, individuals with moderate or high 10-year CHD risk, according to the FRS, had a higher CHD risk (hazard ratio, 6.55; 95% CI, 3.64-11.82) than men with low CHD risk according to the FRS.

Conclusion: Clinicians should promote physical activity to improve CRF so as to reduce CHD risk, even to patients with otherwise low CHD risk.

FIGURE 1

Study flow and Aerobic Center Longitudinal Study (ACLS) inclusion criteria depicting final sample size and coronary heart disease (CHD) event frequency. BMI = body mass index; FRS = Framingham Risk Score.

FIGURE 2

Adjusted hazard ratios (95% CIs) for the relationship between moderate or high 10-year coronary heart disease risk (as classified by the Framingham Risk Score) and coronary heart disease, stratified by low, moderate, and high cardiorespiratory fitness. Low 10-year coronary heart disease risk served as the reference group. ^aAdjusted for baseline examination year