['Diabetes (D) and heart failure (HF) are associated with abnormal heart rate variability (HRV). It is unclear whether the HRV effect of having both is cumulative.', 'Pretreatment HRV (traditional, nonlinear, and heart rate [HR] turbulence) in 80 D versus 74 non-D (ND) systolic HF patients was compared by New York Heart Association II versus III among patients entered into an HF drug evaluation study.', 'Age-adjusted HR was lower in class II D versus class III and most HRV including HR turbulence was better in class II ND versus all others, with few differences between class II D and class III ND and D patients.'] Does new York Heart Association functional class influence the impact of diabetes on cardiac autonomic function?