CALL FOR PAPERS Sex Differences in Renal and Cardiovascular Function: Physiology and Pathophysiology Effect of aging on the cardiovascular regulatory systems in healthy women

Lavi S, Nevo O, Thaler I, Rosenfeld R, Dayan L, Hirshoren N, Gepstein L, Jacob G. Effect of aging on the cardiovascular regulatory systems in healthy women. Am J Physiol Regul Integr Comp Physiol 292: R788–R793, 2007. First published August 31, 2006; doi:10.1152/ajpregu.00352.2006.—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.