Reference values of indices of spontaneous baroreceptor reflex sensitivity

Spontaneous baroreceptor reflex sensitivity (BRS) is a well established met hod for determining baroreflex function, which can be used to assess the po tential impact on survival after myocardial infarction, to detect autonomic dysfunction in diabetic patients and in human essential hypertension. The assessment of impaired spontaneous baroreflex function in individual patien ts contains important clinical information, but age-dependent reference val ues are still lacking. In the present study we evaluated spontaneous BRS in healthy human controls to determine reference values as a function of age. Two hundred and sixty-two healthy volunteers divided into six age groups ( I: <20 years, f = 11, m = 9, II: 20-29 years, f = 42, m = 37, III: 30-39 ye ars, f = 23, m = 37, IV: 40-49 years, f = 27, m 25 V: 50-59 years, f = 19, m = 17, VI: 60-69 years, f = 5, m = 13). Electrocardiograms (ECG) and finge r arterial BP were measured with each subject in the supine position (sup, 7 min) and during deep breathing (dB, 6/min, 15 cycles). BRS was assessed u sing the sequence technique and the alpha coefficients as obtained from a p ower spectrum density estimate. Due to the normal logarithmic distribution of the BRS, the limits for impaired baroreflex function at rest were define d from logarithmic data. The limits for the BRS at rest (P = .025) were cal culated as (-0.0283 x age) + 2.5198 for the sequence technique. We did not find significant differences in BRS among the female and male healthy volun teers. Our analysis of the six age groups showed the expected significant d ecrease in BRS, which was most prominent at the transition from group III ( <40 years) to group IV (<50 years). BRS at rest and during deep breathing a s well as sequential and spectral BRS indices did differ significantly. The results underline the necessity of reference values to evaluate impaired b aroreflex function in individual patients. Am J Hypertens 2000; 13:268-275 (C) 2000 American Journal of Hypertension, Ltd.