6074Cardiorespiratory fitness, socioeconomic status and mortality in middle-aged men: a population-based prospective cohort study

Abstract

Abstract Background Although both low socioeconomic status (SES) and poor cardiorespiratory fitness (CRF) are associated with increased chronic disease and a heightened risk of death, it remains unclear whether moderate-to-high levels of CRF confer survival benefits in low SES populations. Purpose The present study evaluated the hypothesis that SES and CRF predict all-cause mortality (ACM), cardiovascular disease (CVD) mortality and sudden cardiac death (SCD), and that moderate-to-high levels of CRF may attenuate the associations between low SES and adverse cardiovascular outcomes. Methods This prospective study was based on a population-based sample of 2,368 men aged 42 to 61 years, who were followed in the Kuopio Ischemic Heart Disease cohort. CRF was directly measured by peak oxygen uptake (VO2peak) during progressive exercise testing to volitional fatigue. SES was characterized using self-reported questionnaires via combined measures of income, education, occupation, occupational prestige, material standard of living, and housing conditions. CRF and SES were divided into tertiles, and 4 combined groups (Fit-high SES, Fit-low SES, Unfit-high SES, and Unfit-low SES) based on the median values of CRF and SES. Results During a 25 year median follow-up (interquartile ranges: 18–27 years), 1116 ACM, 512 CVD mortality and 221 SCD events occurred. After adjusting for potential confounders (age, smoking, alcohol, body mass index, systolic blood pressure, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, glucose, diabetes, hypertensive medication, family history of coronary heart disease, and physical activity), the lowest levels of SES were at significantly increased risk for ACM (hazard ratio (HR) 1.49, 95% Confidence Interval (CI): 1.30–1.71), CVD mortality (HR 1.38, 1.13–1.69) and SCD (HR 1.34, 0.97–1.84). In contrast, higher levels of CRF were associated with lower risks of ACM (HR 0.56, 0.46–0.67), CVD mortality (HR 0.53, 0.40–0.71) and SCD (HR 0.53, 0.34–0.83). In combined associations of SES and CRF with mortality, unfit-low SES had significantly higher risks of ACM (HR 2.12, 1.75–2.57), CVD mortality (HR 2.20, 1.64–2.94) and SCD (HR 2.95, 1.79–4.86), but fit-low SES was not associated with a heightened risk of cardiovascular mortality or SCD (CVD mortality, 1.03, 0.73–1.46; SCD, 1.54, 0.87–2.72) as compared with their fit-high SES counterparts (reference). Conclusion Our findings indicate that both SES and CRF are independently associated with the risk of death; however, moderate-to-high levels of CRF appear to attenuate the risk of CVD mortality and SCD in low SES men. These unique data have important implications for public health interventions designed to enhance survival in underserved population cohorts.