Autonomic nervous function in essential hypertension in the elderly - Evaluation by power spectral analysis of heart rate variability

Autonomic nervous function in elderly essential hypertensive patients was investigated by power spectral analysis of heart rate variability. Fifty-seven essential hypertensive patients participated in this study. They were divided into two groups: the middle-aged group (age less than or equal to 59 years, n = 30) and the elderly group (age greater than or equal to 60 years, n = 27), All examinations were performed during hospitalization. Power spectral analysis of R-R interval was performed from Holter electrocardiogram every 10 min by the maximum entropy method to obtain the low frequency band (LFB; 0.04 to 0.15 Hz), which is an index of both sympathetic and parasympathetic nervous activity, and the high frequency band (HFB; 0.15 to 0.4 Hz), which reflects parasympathetic nervous activity. Twenty-four-hour blood pressure measurement was performed by the cuff-oscillometric method to evaluate the nocturnal decrease in blood pressure. Nondipper patients were defined as those whose nocturnal decrease in systolic blood pressure was < 10% of daytime blood pressure. Both LFB and HFB were significantly lower in elderly hypertensive patients than in middle-aged patients (P < .001 and P < .05, respectivey). Elderly nondipper patients had further reduced power spectral densities throughout the day. Both LFB and HFB showed a negative correlation with age. However, the age-related decline of power densities was more prominent in dipper patients and was not statistically significant in nondipper patients. These findings indicate that the nondipper phenomenon is superimposed on age-related attenuation of autonomic nervous function in essential hypertension.