AGE AND GENDER DEPENDENCY OF BAROREFLEX SENSITIVITY IN HEALTHY-SUBJECTS

We evaluated the correlates of baroreflex sensitivity (BRS) in healthy subjects. The study consisted of 117 healthy, normal-weight, nonsmoki ng male and female subjects aged 23-77 yr. Baroreflex control of heart rate was measured by using the phenylephrine bolus-injection techniqu e. Frequency- and time-domain analysis of heart rate variability and a n exercise test were performed. Plasma norepinephrine, epinephrine, in sulin, and arginine vasopressin concentrations and plasma renin activi ty were measured. In the univariate analysis, BRS correlated with age (r = -0.65, P < 0.001), diastolic blood pressure (r = -0.47, P-e 0.001 ), exercise capacity (r = 0.60, P < 0.001), and the high-frequency com ponent of heart rate variability (r = 0.64, P < 0.001). There was also a significant correlation between BRS and plasma norepinephrine conce ntration (r = -0.22, P < 0.05) and plasma renin activity (r = 0.32, P < 0.001). According to the multivariate analysts, age and gender were the most important physiological correlates of BRS. They accounted for 52% of interindividual BRS variation. In addition, diastolic blood pr essure and high-frequency component of heart rate variability were sig nificant independent correlates of BRS. BRS was significantly higher i n men than in women(15.0 +/- 1.2 vs. 10.2 +/- 1.1 ms/mmHg, respectivel y; P < 0.01). Twenty-four percent of women >40 vr old and 18% of men > 60 yr old had markedly depressed sits (<3 ms/mmHg). We conclude that p hysiological factors, particularly age and gender, have significant im pact on BRS in healthy subjects. In addition, we demonstrate that BRS values that have been proposed to be useful in identifying postinfarct ion patients at high risk of sudden death are frequently found in heal thy subjects.