The Prognostic Impact of Cardiorespiratory Fitness on Mortality in Diabetes Patients With and Without Left Ventricular Hypertrophy

BACKGROUND: Left ventricular hypertrophy (LVH) and type 2 diabetes mellitus (T2DM) are both independent risk factors for mortality. Cardiorespiratory fitness (CRF) is inversely associated with mortality and independently predicts lower mortality risk in T2DM. However, the relationship between CRF, LVH, and mortality risk in T2DM has not been well characterized and was the focus of this study. METHODS: A total of 866 individuals with T2DM (mean age 61.6 ± 9.9 years) underwent both a standardized exercise stress test and an echocardiographic evaluation. We then established two fitness categories based on peak CRF (i.e., metabolic equivalents (METs)). Individuals with a peak MET level below the median (<6 METs) were considered Low-Fit, and those with a peak MET level at or above the median (≥6 METs) were classified as fit. Left ventricular mass (LVM) was calculated using a standardized formula and indexed to body size to obtain the LVM index. To assess the interaction between fitness and LVH, we established four groups based on fitness status and the presence or absence of LVH: Low-Fit/No LVH (n = 225); Low-Fit/LVH (n = 236); Fit/No LVH (n = 218); and Fit/LVH (n = 187). The Low-Fit/No LVH group served as the reference category for all survival analyses. RESULTS: Over a total of 24 years of follow-up (median 8.9 years), 346 deaths occurred, corresponding to an annual mortality rate of 4.3% in the entire cohort. In the Cox proportional hazards analysis, models adjusted for age, body mass index (BMI), hypertension, smoking, and medication use, revealed a 20% higher mortality risk in the Low-Fit/LVH group (hazard ratio (HR): 1.20; 95% confidence interval (CI): 0.93-1.56; p = 0.15). In contrast, mortality risk was 41% lower in the Fit/No LVH individuals (HR: 0.59; 95% CI: 0.42-0.82; p = 0.002) and 43% lower in the Fit/LVH individuals (HR: 0.57; 95% CI: 0.40-0.81; p = 0.002). CONCLUSIONS: Low-Fit individuals with LVH showed a trend toward higher mortality risk. This risk was significantly mitigated in individuals with moderate fitness regardless of LVH status.