In the first minute, the grade is set at 0% followed by 2% in the second minute and an increase of 1% for every minute thereafter. In this protocol, treadmill speed is set initially at 88 m/min. Body mass index was calculated from measured height and weight.Īs reported previously, 3, 4 fitness was measured in the CCLS by a maximal treadmill exercise test using a Balke protocol. Participants completed a comprehensive clinical examination which included a self-reported personal and family history, standardized medical examination by a physician, fasting blood levels of total cholesterol, triglycerides, and glucose, as well as a maximal treadmill exercise test. In this study, we merged the Cooper Center Longitudinal Study with individual claims data from the Center for Medicare and Medicaid Statistics, allowing for the assessment of the correlation between midlife fitness and the long-term risk for heart failure and acute myocardial infarction.ĭetails of the clinical examination and the study cohort have been published previously. Therefore, we hypothesized that lower levels of fitness in healthy, middle-aged adults would be more strongly associated with heart failure hospitalization than with hospitalization for acute myocardial infarction. 17, 20 While much of the focus on the mechanisms of benefit of exercise and fitness have focused on prevention of atherosclerosis and its complications, the specific effects of exercise on cardiac structure and function suggest that low fitness might be particularly important for long-term heart failure risk. 18, 19 In addition, lifelong exercise training appears to limit age-related cardiac stiffening, resulting in a more compliant left ventricle in older age and possibly reducing the risk of heart failure with preserved ejection fraction. 11, 12 Although higher fitness is associated with lower levels subclinical atherosclerosis, 13- 15 exercise also has measurable, biological effects on cardiovascular structure and function 16, 17 that are highly responsive to short-term changes in exercise. The mechanism through which low fitness associates with adverse cardiovascular outcomes across the lifespan likely reflects in part the subsequent development of traditional risk factors such as diabetes and hypertension. 9 However, the association between fitness and non-fatal cardiovascular events is not well understood, 8, 10 reflecting the lack of data on non-fatal cardiovascular events among established cohorts with objectively measured fitness levels. 3- 8 This association persists across the lifespan, with a single measurement of fitness in mid-life strongly associated with the lifetime risk for cardiovascular mortality decades later. 1, 2 Fitness is strongly associated with lower cardiovascular disease mortality, with multiple studies demonstrating a consistent, inverse association between fitness and mortality even after adjustment for traditional risk factor burden. Higher cardiorespiratory fitness (fitness) is a reflection of habitual physical activity in adults. After multivariable adjustment for baseline age, blood pressure, diabetes, body mass index, smoking status and total cholesterol, a 1 unit greater fitness level in metabolic equivalents (METs) achieved in midlife was associated with approximately a 20% lower risk for heart failure hospitalization after age 65 but just a 10% lower risk for acute myocardial infarction in men and no association in women. 4.2%) and hospitalization for myocardial infarction (9.7% vs. Compared to high fitness (Q4-5), low fitness (Q1) was associated with a higher rate of heart failure hospitalization (14.3% vs. After 133,514 person-years of Medicare follow-up, we observed 1,051 hospitalizations for heart failure and 832 hospitalizations for acute myocardial infarction. Associations between midlife fitness and hospitalizations for heart failure and acute myocardial infarction after age 65 were assessed by applying a proportional hazards model to the multivariate failure time data. Fitness was also estimated in metabolic equivalents according to treadmill time. Fitness was categorized into age- and sex-specific quintiles (Q) according to Balke protocol treadmill time with Q1 as low fitness. Linking individual participant data from the Cooper Center Longitudinal Study with Medicare claims files, we studied 20,642 participants (21% women) with fitness measured at mean age 49 years and who survived to receive Medicare coverage from 1999 to 2009.
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