Spectral analysis of heart rate variability in elderly non-dipper hypertensive patients

To assess by autoregressive model the frequency domain heart rate variability (HRV) during clinostatism and after passive orthostatic load (head-up tilt), 81 hypertensive and normotensive subjects (42 men and 39 women) were subdivided into four groups: 20 adult normotensive subjects (Group 1); 21 elderly normotensive subjects (Group 2); 20 elderly hypertensive subjects with nocturnal blood pressure (BP) falls (Group 3); and 20 elderly hypertensive subjects without nocturnal BP falls (Group 4). They were chosen to assess the influence of aging and arterial hypertension on sympathetic-parasympathetic balance. The age-related decrease observed in nearly all HRV spectral frequency components (normalised units [NUs], high frequency [HF] and low frequency [LF]) was reported in elderly patients in rest conditions. LF indexes resulted in decreases in Group 3 and these data seemed to be emphasised in Group 4. After passive tilt, spectral data were recorded as follows: 25.3 ± 1.8 vs17.8 ± 2.2 HF, Group 2 vs Group 1, P < 0.001; 72.5 ± 0.8 vs 75.6 ± 1.8 LF, P < 0.001, group 2 vs Group 1. Both sympathetic and parasympathetic indexes were lower in Group 3 (44.6 ± 1.1 vs72.5 ± 0.8 LF, P < 0.001, group 3 vs Group 2; 9.9 ± 1.8 vs 25.3 ± 1.8 HF, P < 0.001, group 3 vs Group 2) and data became clearer in Group 4 (8.5 ± 2.1 vs 9.9 ± 1.8 HF, P < 0.001; 40.4 ± 1.5 vs44.6 ± 1.1 LF, Group 4 vs Group 3). The established influence of aging on autonomic nervous system activity appears to be increased by arterial hypertension due to worsening of the sympathetic-parasympathetic response to standardised stimulation. The loss of nocturnal BP declines in arterial hypertension was found to occur in association with a decrease in autonomic nervous system activity.