Autonomic nervous system activity in dipper and non-dipper essential hypertensive patients. What about sex differences?

Objectives To compare the autonomic nervous system activity indexes obtaine d from photoplethysmography in dipper and non-dipper hypertensive patients and to seek a potential influence of sex on the relation between autonomic nervous system and the nocturnal decrease in blood pressure. Methods We studied 245 hypertensive patients, who underwent 24 h ambulatory blood pressure monitoring (ABPM), photoplethysmographic blood pressure rec ording, and echocardiography, Non-dipping patients were defined as those wh ose nocturnal decrease in systolic blood pressure (SBP), diastolic blood pr essure (DBP), or both was less than 10% of the daytime blood pressure. Spec tral powers of SBP, DBP and heart rate were obtained from photoplethysmogra phic recordings over three main frequency bands: very low frequency (0.005- 0.05 Hz), low frequency (0.05-0.14 Hz) and high frequency (0.14-0.40 Hz). Results Because their ABPM were normal (less than 135/85 mmHg; n = 33), of poor quality (n = 22) or performed at a period too far from the photoplethy smographic recording (n = 17), 66 patients were excluded from the analysis. The remaining 179 patients comprised 117 dippers and 62 non-dippers. The g roups did not differ regarding clinical and echocardiographic characteristi cs, irrespective of sex. Low-frequency spectral powers were significantly l ower in non-dippers than in dippers, whatever the signal, whereas high-freq uency spectral powers did not differ significantly between the groups. The nocturnal decrease in blood pressure increased with increasing low-frequenc y spectral powers, but was negatively correlated with high-frequency spectr al powers. Multivariate linear regression analysis identified low-frequency spectral power of SEP and clinic DBP as independent factors determining th e decrease in blood pressure. After adjustment for all significant covariat es, the odds of being a non-dipper did not differ between men and women. Conclusion A non-dipper profile seemed to be associated, in both men and wo men, with lower low-frequency spectral powers compared with those in dipper s, suggesting impaired sympathetic arterial modulation. J Hypertens 1999, 1 7:1805-1811 (C) Lippincott Williams & Wilkins.