Autonomic control of heart period and QT interval variability during the aging process

Aging is associated with autonomic nervous system (ANS) impairment. Heart period variability (HPV) analysis suggested a decrease of the parasympathetic modulation and an increase of the sympathetic one with age. In addition, the variability of the time interval between Q-wave onset and T-wave end (QTV) has been used to evaluate the sympathetic modulation directed to ventricles. The aim of this study is to evaluate the age-related changes in QTV and compare them with those of HPV. We studied 111 male subjects divided into five groups according to the age ranges: 20-29; 30-39; 40-49; 50-59; 60-69. We assessed the ANS modulation directed to the sinus node and to the ventricles at rest in supine position (REST) and during active standing (STAND) via time and frequency domain HPV and QTV indexes. Lower values of σ2 HP and HFaHP, and higher values of σ2 QT and LFaQT at REST were observed specially in the last two decades compared to the youngest one. STAND reduced further the HP values and increased further these QT values. Our findings showed that both HPV and QTV are age-dependent, with the most significant QTV alterations occurring in the late bins of age. Spectral analyses of HPV and QTV suggest a reduced vagal and increased sympathetic modulations with age.