[Evaluation of the activity of the autonomic nervous system in "dipper" and "non dipper" essential hypertensives. Gender differences].

Objectives : 1) To compare the autonomic nervous system activity parameters obtained from a photoplethysmographic recording in dipper and non dipper hypertensives. 2) To look for an interaction between dipper Inon dipper status and gender. Methods : Prospective study involving 245 untreated hypertensives (51 ± 13 years, 146 men, 99 women). All of the patients underwent a 24-hour ambulatory blood pressure measurement (ABPM) as well as an echocardiography for left ventricular mass index determination (LVMI) and a photoplethysmographic recording of blood pressure (BP). Nondippers were defined as those whose nocturnal decrease in systolic BP (SBP) and/or diastolic BP (DBP) was < 10% of daytime BP. Spectral powers were obtained from the photoplethysmographic recording using a fast Fourier transform over the low frequency band (LF) and the high frequency band (HF). Baroreflex sensitivity (BRS) was evaluated by the sequences method. Results: Of the 245 patients. 1S9 were dippers (98 men, 61 women) and 86 were non dippers (48 men and 38 women). Clinic BP was significantly higher in non dippers than in dippers (168 /101 vs 161/98 mmHg; p<0.01 for SBP and p<0.05 for DBP) whereas daytime ABPM and LVMI were not different, whatever the gender. LF spectral powers were significantly lower in non dippers than in dippers for SBP (respectively 25±11% vs 30±13%; p<0.01) for DBP (respectively 35±14% vs 41±15%; p<0.01) and for HR (respectively 34±15% vs 38±15%; p=0.03). They showed a positive correlation with the nocturnal SBP fall (r=0.21. p<0.001 for SBP and DBP spectral powers, r=0.19: p<0.005 for HR spectral power) and with the nocturnal DBP fall, too (r=0.19; p<0.005 for SBP spectral power, r=0.20; p<0.002 for DBP spectral power, r=0.19: p<0.005 for HR spectral power). HF spectral powers tended to be higher in non dippers than in dippers but in a non significative way. BRS was roughly the same in dippers and non dippers (7.5±2.7 vs 7.0± 3.1 ms/mmHg, NS). The interaction between non dipper/dipper status and sex was non significant whatever the LF spectral power. Conclusions: 1) The greater the nocturnal BP fall, the higher the sympathetic activity indexes. 2) This relationship was found both in males and females.