OBJECTIVE: To assess the relationships between serum dehydroepiandrosterone sulfate (DHEA-S) levels and heart rate variability (HRV) among different age groups. SUBJECTS AND METHODS: Forty-five healthy men were divided into 3 groups: young age (YA; 20-39 yrs; n = 15), middle age (MA; 40-59 yrs; n = 15) and old age (OA; >/= 60 yrs; n = 15). Hemodynamic parameters, linear analyses of HRV and concentrations of cortisol and DHEA-S were measured at rest. RESULTS: The OA group presented a higher resting heart rate (84.3 +/- 4.6 bpm) than the YA group (72.0 +/- 4.4 bpm; p < 0.05). The YA group showed an attenuated variance of HRV (2235.1 +/- 417.9 ms2) compared to the MA (1014.3 +/- 265.2 ms2; p < 0.05) and OA (896.3 +/- 274.1 ms2; p < 0.05) groups, respectively. The parasympathetic modulation of HRV was lower in both the MA (244.2 +/- 58.0 ms2) and OA (172.8 +/- 37.9 ms2) groups in comparison with the YA group (996.0 +/- 255.4 ms2; p < 0.05), while serum DHEA-S levels were significantly lower in both the MA (91.2 +/- 19.6 mg/dL) and OA (54.2 +/- 17.7 mg/dL) groups compared to the YA group (240.0 +/- 50.8 mg/dL; p < 0.05). A positive correlation between lower serum concentrations of DHEA-S and attenuated variance of HRV (r = 0.47, p = 0.031), as well as lower serum concentrations of DHEA-S and decreased parasympathetic modulation of HRV (r = 0.54, p = 0.010), were found. CONCLUSION: The present study demonstrated that the decline of plasma DHEA-S is associated with reduced cardiac autonomic modulation during the aging process.