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

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.

Assessment of Heart Rate Variability in Early Post-menopausal Women

“…[7] In a study by Neufeld et al [20] RMSSD was significantly higher in postmenopausal women, which could be due to difference in BMI or regular physical activity in their subjects (which is not mentioned), as physically active postmenopausal women are reported to have higher vagal tone compared to sedentary and less active postmenopausal women. [21] Our result is similar to reports of Neves VF and Ribeiro TF, [7,22] where significant decrease in RMSSD was observed in postmenopausal women. Thus, there was vagal withdrawal after menopause.…”

“…These findings were in conformity with the earlier study which showed similar results in postmenopausal group without estrogen therapy when compared to premenopausal group. [22] So, our study demonstrated a shift of autonomic functions in postmenopausal women, who tend to move towards sympathetic over activity and vagal withdrawal compared to premenopausal women. Further in this study, there was considerable decrease in vagal indices in postmenopausal women which is known to increase the risk of cardiovascular disease.…”

Aging, Heart Rate Variability and Metabolic Impact of Obesity

“…In contrast to this, in our investigation MHO women had higher HFnorm and lower LF/HF and LFnorm compared to MHO men, while in MUO subjects there were no sex differences in HRV markers (not shown in tables). Tendency of HRV decrease in female is connected to lowering of the estrogen level in menopause 14 . Unlike women, men do not experience sudden decline in sex hormones during aging 15 .…”

Existe influência do nível de atividade física habitual na capacidade aeróbia e variabilidade da frequência cardíaca em mulheres na fase da pós menopausa?

“…Além disto, já se sabe que o número de passos diários tendem a diminuir com o avançar da idade 8 , bem como VO 2 max sobretudo para o sexo feminino 30 . Deste modo, os prejuízos do envelhecimento associados a diminuição do NAFH representam grandes problemas para saúde das mulheres, notoriamente na fase da pós menopausa, como aumento da pressão arterial, aumento do estresse oxidativo, diminuição da massa óssea e muscular, aumento de risco de câncer, queda de cabelo, diminuição de libido, diminuição do gasto calórico, aumento da ansiedade e risco de depressão, aumento no ganho de peso e deficiência de estrogênio 31 acarretando em alteração no sistema barorreflexor da FC 32 .…”