Autonomic modulation of heart rate of young and postmenopausal women undergoing estrogen therapy

Author(s)

V.F.C. Neves ^[1] ; M.F. Silva de Sá ^[2] ; L. Gallo Jr. ^[3] ; A.M. Catai ^[4] ; L.E.B. Martins ^[5] ; J.C. Crescêncio ^[6] ; N.M. Perpétuo ^[7] ; E. Silva

Affiliation

^[1] Universidade Federal de São Carlos. Departamento de Fisioterapia. Laboratório de Fisioterapia Cardiovascular - Brasil

^[2] Universidade de São Paulo. Faculdade de Medicina de Ribeirão Preto. Departamento de Ginecologia e Obstetrícia

^[3] Universidade de São Paulo. Faculdade de Medicina de Ribeirão Preto. Hospital das Clínicas - Brasil

^[4] Universidade Federal de São Carlos. Departamento de Fisioterapia. Laboratório de Fisioterapia Cardiovascular - Brasil

^[5] Universidade Estadual de Campinas. Faculdade de Educação Física. Laboratório de Fisiologia do Exercício - Brasil

^[6] Universidade de São Paulo. Faculdade de Medicina de Ribeirão Preto. Hospital das Clínicas - Brasil

^[7] Universidade Metodista de Piracicaba. Faculdade de Ciências da Saúde. Laboratório de Pesquisa em Fisioterapia Cardiovascular e de Provas Funcionais - Brasil

• Document type: Journal article
• Source: Brazilian Journal of Medical and Biological Research; v. 40, n. 4, p. 491-499, 2007-02-07.

Abstract

The aim of the present study was to determine whether estrogen therapy (ET) reduces alterations of the autonomic control of heart rate (HR) due to hypoestrogenism and aging. Thirteen young (24 ± 2.6 years), 10 postmenopausal (53 ± 4.6 years) undergoing ET (PM-ET), and 14 postmenopausal (56 ± 2.6 years) women not undergoing ET (PM) were studied. ET consisted of 0.625 mg/day conjugated equine estrogen. HR was recorded continuously for 8 min at rest in the supine and sitting positions. HR variability (HRV) was analyzed by time (SDNN and rMSSD indices) and frequency domain methods. Power spectral components are reported as normalized units (nu) at low (LF) and high (HF) frequencies, and as LF/HF ratio. Intergroup comparisons: SDNN index was higher in young (median: supine, 47 ms; sitting, 42 ms) than in PM-ET (33; 29 ms) and PM (31; 29 ms) women (P < 0.05). PM showed lower HFnu, higher LFnu and higher LF/HF ratio (supine: 44, 56, 1.29; sitting: 38, 62, 1.60) than the young group in the supine position (61, 39, 0.63) and the PM-ET group in the sitting position (57, 43, 0.75; P < 0.05). Intragroup comparisons: HR was lower in the supine than in the sitting position for all groups (P < 0.05). The HRV decrease from the supine to the sitting position was significant only in the young group. These results suggest that HRV decreases during aging. ET seems to attenuate this process, promoting a reduction in sympathetic activity on the heart and contributing to the cardioprotective effect of estrogen hormones. (AU)