SPORT MEDICINE JOURNAL CLUB Fitness and Cardiovascular Events in Asymptomatic Men and Women

Objective: To investigate the relation between cardiorespiratory fitness (CRF) and nonfatal cardiovascular disease (CVD) events in asymptomatic men and women. Design: Cohort study with a mean follow-up period of ~10 years. Setting: Community study (Aerobics Center Longitudinal Study) of persons attending the Cooper Clinic, Dallas, Texas. Participants: Men (n = 20,728) and women (n = 5909) who attended a baseline examination during 1971–2001, were 18–83 years of age, free of known CVD, had normal resting electrocardiograms, completed an exercise stress test to$85% of age-predicted maximal heart rate, and who returned $1 mail-back health survey in 1982, 1999, and 2004 were included in the study. Assessment of risk factors: The baseline clinical examination included measurement of body mass index, blood pressure, serum lipids and glucose, and information on lifestyle factors and personal and family health history. CRF was measured as the duration of a symptomlimited maximal treadmill exercise test to volitional exhaustion. Low, moderate, and high CRF were defined by the lowest 20%, the middle 40%, and the upper 40% of the age and sex-specific distribution of the sample. Abnormal electrocardiogram responses were noted. Main outcome measures: The primary outcome measure was all physiciandiagnosed CVD events (myocardial infarction, stroke, or a coronary revascularization procedure), reported on the follow-up questionnaires, in relation to baseline CRF. Baseline health histories and mortality rates between responders and nonresponders were compared and found to be similar (aggregate response rate, ~65%). Main results: During 215,984 manyears of exposure 1512 CVD events (489 myocardial infarctions, 290 strokes, and 733 revascularizations) occurred and during 60,158 woman-years of exposure 159 CVD events (53 myocardial infarctions, 62 strokes, and 44 revascularizations) occurred. Overall, persons who developed CVD were older, had lower CRF, and had a greater prevalence of major CVD risk factors. Rates of CVD per 10,000 person-years, adjusted for age and year of examination, among men were 107.9, 75.2, and 50.3 for low, moderate, and high CFR groups (P for trend, , 0.001). After adjustment for all other CVD risk factors, and compared with the low CRF group, hazard ratios (HR) were 0.89 (95% CI, 0.78–1.02) and 0.75 (CI, 0.64–0.87) for the moderate and high CRF groups (P for trend, 0.001). Rates of CVD for women were 41.9, 27.7, and 20.8 for the low to high CRF groups (P for trend, 0.002). Among women, fully adjusted HR were 0.83 (CI, 0.54–1.28) and 0.78 (CI, 0.49–1.23) for the moderate and high CRF groups (P for trend, 0.30). Among men, when coronary heart disease (myocardial infarction and revascularization), myocardial infarction alone, and stroke were considered separately, HR remained lower for the moderate and high CRF groups (P for trends, #0.04) whereas, among women, although rates for each event were highest in the low CRF group, no statistical associations were found in the adjusted HR between CVD categories and CRF (P for trend, $0.40). Men who reported sedentariness (no leisure-time physical activity in the previous 3 mo) had a higher rate per 10,000 person-years of total CVD events than those who did not (rate, 78.4 vs. 64.8; P , 0.001), but among women an inverse association was not found (sedentary CVD rate, 22.3 vs active, 28.5; P = 0.20). Adjustment for sedentary/active status did not modify the trends for an inverse association between CRF and CVD events. Conclusions: Greater cardiorespiratory fitness predicted a lower risk of a nonfatal cardiovascular disease event in the following 10 years. The association was stronger in men than in women.