Determinants of spontaneous baroreflex sensitivity in a healthy working population

Baroreflex sensitivity (BRS) by the spontaneous sequence technique has been widely used as a cardiac autonomic index for a variety of pathological con ditions. However, little information is available on determinants of the va riability of spontaneous BRS and on age-related reference values of this me asurement in a healthy population. We evaluated BRS as the slope of spontan eous changes in systolic blood pressure (BP) and pulse interval from 10 min utes BP (Finapres) and ECG recordings in 1134 healthy volunteers 18 to 60 y ears of age. Measurement of BRS could be obtained in 90% of subjects. Those with unmeasurable spontaneous BRS had a slightly lower heart rate but were otherwise not different from the rest of the population. BRS was inversely related to age (InBRS, 3.24-0.03 x age; r(2)=0.23; P<0.0001) in both gende rs. In addition, univariate analysis revealed a significant inverse correla tion between BRS and heart rate, body mass index, and BP, Sedentary lifesty le and regular alcohol consumption were also associated with lower BRS. How ever, only age, heart rate, systolic and diastolic BP, body mass index, smo king, and gender were independent predictors of BRS in a multivariate model , accounting for 47% of the variance of BRS. The present study provides ref erence values for spontaneous BRS in a healthy white population. Only appro ximately half of the variability of BRS could be explained by anthropometri c variables and common risk factors, which suggests that a significant prop ortion of interindividual differences may reflect genetic heterogeneity.