Impact of Cardiorespiratory Fitness on Survival in Men with Low Socioeconomic Status

Aims: Although both low socioeconomic status (SES) and poor cardiorespiratory fitness (CRF) are associated with increased chronic disease and heightened mortality, it remains unclear whether moderate-to-high levels of CRF are associated with survival benefits in low SES populations. This study evaluated the hypothesis that SES and CRF predict all-cause mortality (ACM) and cardiovascular disease (CVD) mortality and that moderate-to-high levels of CRF may attenuate the association between low SES and increased mortality.

Methods: This study included 2,368 men, who were followed in the Kuopio Ischemic Heart Disease Study cohort. CRF was directly measured by peak oxygen uptake during progressive exercise testing. SES was characterized using self-reported questionnaires.

Results: During a 25-year median follow-up, 1116 ACM and 512 CVD mortality events occurred. After adjusting for potential confounders, men with low SES were at increased risks for ACM (hazard ratio [HR] 1.49, 95% Confidence Interval [CI]: 1.30-1.71) and CVD mortality (HR 1.38, 1.13-1.69). Higher levels of CRF were associated with lower risks of ACM (HR 0.54, 0.45-0.64) and CVD mortality (HR 0.53, 0.40-0.69). In joint associations of SES and CRF with mortality, low SES-unfit had significantly higher risks of ACM (HR 2.15, 1.78-2.59) and CVD mortality (HR 1.95, 1.48-2.57), but low SES-fit was not associated with a heightened risk of CVD mortality (1.09, 0.80-1.48) as compared with their high SES-fit counterparts.

Conclusion: Both SES and CRF were independently associated with subsequent mortality; however, moderate-to-high levels of CRF were not associated with an excess risk of CVD mortality in men with low SES.