Combined effects of exercise capacity and coronary atherosclerotic burden on all-cause mortality in asymptomatic Koreans

Background and aims Both exercise capacity and coronary artery calcium score (CACS) are important prognostic factors in cardiovascular outcome. Yet, whether there is a significant interaction between these two factors in influencing clinical outcome is still uncertain. This study investigated the combined effects of exercise capacity and CACS on all-cause mortality in an asymptomatic population. Methods From multicenter registry of health screening, a retrospective cohort of 25,972 asymptomatic subjects, who underwent both CACS and treadmill exercise test, was included in the final dataset for analysis. Outcome was defined as all-cause mortality, which was obtained from national mortality registry. Results The mean age of study subjects was 53.7 ± 7.7 years and 81.5% of them were males. Median follow-up duration was 5.5 (IQR 3.6–7.5) years and 226 (0.9%) cases of all-cause mortality occurred. In multivariate Cox's proportional hazard model with interaction term, exercise capacity ≥10 METs (HR 0.684, 95% CI 0.483–0.971) and CACS ≥400 (HR 3.328, 95% CI 1.850–5.988) were significant predictors of all-cause mortality. In patients with higher exercise capacity, the effect of high CACS on all-cause mortality was significantly smaller than in those with lower exercise capacity. The HR for all-cause mortality of CACS ≥400, in those with lower exercise capacity, is estimated to be about three times of that in those with higher exercise capacity (HR 3.328 in <10 METs vs. 1.108 in ≥10 METs, p for interaction = 0.024) after adjustment for age, gender, fasting glucose, creatinine, alanine transaminase and albumin. Conclusions The effect of high CACS on all-cause mortality is lessened by good exercise capacity in the asymptomatic population. Good physical fitness may reduce the adverse effect of high coronary atherosclerotic burden.