The peak VO2 was lower in the diabetics versus the nondiabetics in the non-reduced LVEF cohort with the mean difference (95% confidence interval [95% CI]) of − 0.93 (− 1.82 to − 0.04) mL/kg/min and in the reduced LVEF cohort with the mean difference of − 1.05 (− 1.96 to − 0.15) mL/kg/min, after adjustment for age-squared, gender, anemia, renal function, LVEF, and log B-type natriuretic peptide (BNP). This evidence concerns the gene NPPB and anemia.