Effect of aging on the cardiovascular regulatory systems in healthy women

1 J. Recanati Autonomic Dysfunction Center, Medicine A, Departments of 2 Cardiology and 3 Obstetrics and Gynecology, Rambam Medical Center, Faculty of Medicine, Technion-Israel, Institute of Technology, Haifa Israel Submitted 25 May 2006 ; accepted in final form 29 August 2006 Aging, independently from the hormonal status, is a major risk factor for cardiovascular morbidity in healthy women. Therefore, we studied the effect of healthy aging on the cardiovascular homeostatic mechanisms in premenopausal and postmenopausal women with similar estrogen levels. Twelve healthy postmenopausal women, confirmed by follicular-stimulating hormone (FSH) and luteal hormone (LH) levels, were compared with 14 normally menstruating women during the early follicular phase (young-EF), to avoid as much as possible the effects of estrogen. Systolic BP was 108 ± 1.5 vs. 123 ± 2.5 ( P < 0.001), supine norepinephrine was 260 ± 30 vs. 216 ± 45 and upright 640 ± 100 vs. 395 ± 50 pg/ml ( P = 0.05) in young-EF vs. postmenopausal, respectively. Plasma renin activity and aldosterone remained unchanged. Vagal cardiac tone indices decreased significantly with aging (young-EF vs. postmenopausal): high-frequency (HF) band, root mean square successive differences (rMSSD) and proportion of R-R intervals >50 ms (PNN50%) were 620 ± 140 vs. 270 ± 70 ( P = 0.04), 53 ± 7 vs. 30 ± 3 ( P = 0.02), and 23 ± 5 vs. 10 ± 3 ( P = 0.04), respectively. LF to HF ratio was 0.85 ± 0.17 in young-EF and became 1.5 ± 0.22 in postmenopausal ( P = 0.03). Both arms of the baroreflex, +BRS (29 ± 5 vs. 13.5 ± 2.5, P = 0.01) and –BRS (26 ± 4 vs. 15 ± 1.5, P = 0.02) decreased with aging. Cardiovascular 1 -adrenoreceptor responsiveness significantly increased and -decreased in postmenopausal compared with young EF ( P < 0.001, both). The corrected QT intervals (QTc) were similar, whereas corrected JT intervals (JTc) and JTc to QTc ratio were prolonged in the postmenopausal group. We conclude that in young women, parasympathetic control is the main regulator of the cardiovascular system and in postmenopausal women, sympathetic tone dominates. The transition from parasympathetic to sympathetic control may contribute to the increased cardiovascular morbidity with aging. autonomic nervous system; baroreflex; renin; QT interval Address for reprint requests and other correspondence: G. Jacob, J. Recanati Autonomic Dysfunction Center, Medicine A, Rambam Medical Center, Haifa 31096 Israel (e-mail: g_jacob{at}rambam.health.gov.i