Determinants of Maximal Oxygen Consumption in Cardiac Rehabilitation Patients: The Role of Sex

Objectives: We aimed to assess sex differences in benefits from cardiac rehabilitation and the impact of comorbidities. Methods: We analyzed 3239 individuals with cardiovascular diseases (81.2% males) who participated in a three-week cardiac rehabilitation program at Bad Schallerbach center (Upper Austria). Training success was measured by maximal oxygen consumption (VO2 max). Sex-specific differences in baseline characteristics were assessed using t-tests/chi2 tests. Associations between covariates and the outcome were evaluated with baseline-adjusted univariate analysis of variance/linear regression models. Covariates significant at α = 0.05 were included in a multivariable linear regression model, which was refined by backward selection based on the best Akaike information criterion. The final model was used to test the relationship between sex and the outcome. Results: The mean age and BMI were 63.9 years and 27.5 kg/m2 for males and 67.2 years and 27.4 kg/m2 for females. Males had higher baseline VO2 max compared to females (26.18 mL/min/kg vs. 23.55 mL/min/kg, p < 0.001), and a greater change in VO2 max after rehabilitation was seen in males compared to females (3.64 mL/min/kg vs. 2.77 mL/min/kg, p < 0.001). Female sex was associated with a 1.4-point-lower change in VO2 max after adjustment for comorbidities, sex, and training intensity (β coefficients = −1.409; CI 95% −0.410, −0.104; p < 0.001). Heart valve surgery (β coefficients = −0.90; CI 95% −1.444, −0.366; p < 0.001) and diabetes mellitus (β coefficients = −1.207; CI 95% −1.926, −0.488; p < 0.0001) were associated with lower changes in VO2 max in both sexes. Conclusions: Our findings suggest that females and individuals with specific comorbidities benefit less from cardiac rehabilitation and support the creation of personalized rehabilitation programs.