Background: Multiple studies have demonstrated a strong association between cardiorespiratory fitness and increased morbidity and mortality. However, it is less clear whether cardiovascular fitness is an independent predictor for the development of cardiovascular disease (CVD) in apparently healthy middle-aged adults or merely a marker of associated comorbidities and risk factors.
Methods: We investigated 11607 men and women who were annually screened at the Institute for Medical Screening of the Chaim Sheba Medical Center. All subjects were free of ischemic heart disease, and had completed maximal exercise stress tests (EST) according to the Bruce protocol at their first visit. Fitness was categorized into quintiles (Q) according to EST time duration with Q4 as having excellent fitness. Subjects were divided at baseline into two groups: excellent fitness (>725 seconds, Q4) vs. all other subjects (<725 seconds, Q1-3). The primary endpoint of the current analysis was a composite of symptoms-driven percutaneous coronary intervention and acute coronary syndrome.
Results: Mean age of study patients was 48 ± 10 years and Z4% were men. A total of 446 (4%) events occurred during a mean follow up of 7±3 years. Kaplan Meier survival analysis showed that the cumulative probability of cardiovascular events at 7 years was significantly lower among subjects with excellent fitness (Unadjusted log-rank P < 0.001;Figure1). However, after multivariate adjustment for other known cardiovascular risk factors, including age, gender,obesity, hypercholesteremia, low high density lipoprotein-cholesterol HDL-C, and diabetes mellitus, excellent fitness was no longer significantly associated with reduced risk for cardiovascular events (HR = 0.78 [95% CI 0.58-1.05], p=0.10).
Conclusions: Our findings suggest that the correlation between cardiovascular fitness in apparently healthy middle-aged adults and subsequent cardiovascular risk may be related to the presence of associated risk factors.
