Physical Activity, Fitness, and Coronary Heart Disease

Abstract

Coronary heart disease (CHD) and its clinical complications are preventable through established primary or secondary interventions. Strong and clear evidence indicates that higher levels of self-reported physical activity and measured cardiorespiratory fitness have been observed in epidemiologic studies to be associated with lower incidence CHD. The inverse association exhibits a curvilinear dose-response gradient with the largest differences in CHD risk demonstrated when comparing those in the lowest activity or fitness category with those who are only modestly more active and fit. This general pattern of association is consistent among population subgroups including women and men, older adults, race-ethnic minorities, and those who have increased CHD risk due to the presence of existing morbidity. Available evidence supports promotion of guideline-recommended amounts of physical activity (≈8 MET-h/week in moderate-to-vigorous activities). Individuals achieving this level of physical activity experience, on average, a 14–20% lower risk of CHD as compared to their inactive peers. The cardioprotective benefit of higher levels of cardiorespiratory fitness is somewhat stronger than for self-reported physical activity, perhaps due in part to less measurement error associated with fitness assessment. While no gold standard classification currently exists to classify “recommended cardiorespiratory fitness level,” many observational epidemiologic studies have demonstrated substantially lower CHD risk (e.g., 35–50% lower risk) among adults in the middle two fifths of the age- and sex-standardized distribution of achieved metabolic equivalents during incremental exercise ergometry testing, as compared to those in the lowest fifth of the distribution. The MET values that separate the lowest and middle two fifths of cardiorespiratory fitness distributions are about 7–10 METs in men and 6–8 METs in women, ages 20 to 60 years. Because of the high population prevalence of physical inactivity and low cardiorespiratory fitness, and given the moderate strength of association these phenotypes have with CHD incidence, the fraction of CHD risk attributed to inactivity and low fitness is substantial and rivals that of conventional CHD risk factors such as hypertension, hypercholesterolemia, and smoking. Because improvements in physical activity tend to favorably influence blood lipids, blood pressure, insulin sensitivity, and hemostatic factors as well as cardiorespiratory fitness, next to quitting smoking, increasing and maintaining one’s physical activity level at recommended levels is one of the least expensive and most beneficial approaches to achieving cardiometabolic health and reducing CHD risk available to the public.