NPPB and anemia: After the adjustment for age-squared, gender, anemia, renal function, LVEF, and log BNP, the peak VO2 was lower in the diabetics compared to the nondiabetics among the patients with LVEF ≥ 40%, with the mean difference (95% CI) of − 0.93 (− 1.82 to − 0.04) mL/kg/min; the peak VO2 was also lower in the diabetics compared to the nondiabetics among the patients with LVEF < 40%, with the mean difference of − 1.05 (− 1.96 to − 0.15) mL/kg/min.