Factors associated with baroreflex sensitivity: association with morning blood pressure

Baroreflex sensitivity (BRS) is a primary mechanism for acute and chronic control of blood pressure (BP). However, there are few data showing the relationship between BRS and ambulatory BP (ABP). We assessed the hypothesis that BRS specifically contributes to some specific parameters of ABP in never-treated hypertensive/normotensive subjects. We studied 128 subjects (mean age: 54.5+/-13 years, 60% male) consisting of 92 untreated hypertensive and 36 normotensive subjects. Radial tonometric BP and simultaneous RR interval were recorded for 10 min, and the Valsalva maneuver was performed 3 times for each subject. BRS was calculated in two ways: the spontaneous-BRS by the spectral method, and the Valsalva-BRS by the slope method, using commercial software. ABP monitoring was performed on the same day as the BRS test. Of 128 subjects, we obtained BRS from 111 subjects with the Valsalva method and 123 subjects with the spontaneous method. Univariate analyses showed that the Valsalva-BRS was negatively correlated only with morning systolic BP (r=-0.21, p=0.03). Multivariable analyses showed that the Valsalva-BRS (ms/mmHg) was independently associated with the morning systolic BP (beta=-0.26, p=0.022), even after adjusting for age, sex, body mass index, presence of diabetes, duration of hypertension, clinic systolic BP and pulse rates. The spontaneous-BRS estimates were inversely correlated with clinic pulse rates in the same model. In conclusion, impaired BRS evaluated by the Valsalva method was associated with high morning BP level, independent of other confounders. Morning hypertension might be partly mediated by impaired BRS.