Sympathetic nerve hyperactivity of essential hypertension is lower in postmenopausal women than men

Abstract

Sympathetic activation has been associated with the development and complications of hypertension. While the prevalence of hypertension and its cardiovascular risks in women are found to be less than in men and tend to become similar to men after the menopause, there have been no data on the level of sympathetic activation in postmenopausal women relative to men. Therefore, we planned to find out whether muscle sympathetic nerve hyperactivity of essential hypertension (EHT) in postmenopausal women is different from that in matched men. We quantified muscle sympathetic nerve activity (MSNA) as mean frequency of single units (s-MSNA) and multiunit bursts (b-MSNA) in 21 postmenopausal women with EHT (W-EHT) relative to 21 matched men with EHT (M-EHT), in comparison to two control groups of 21 normal women (W-NC) and 21 men (M-NC), respectively. The EHT groups had greater MSNA indices than NC groups. W-EHT had lower (Po0.05) s-MSNA (63 ± 22.7 impulses per 100 cardiac beats) than M-EHT (78 ± 11.2 impulses per 100 cardiac beats). W-NC had lower (Po0.05) s-MSNA (53 ± 12.4 impulses per 100 cardiac beats) than M-NC (65±16.3 impulses per 100 cardiac beats). Similar results were obtained for b-MSNA. Postmenopausal women with EHT had lower level of central sympathetic hyperactivity than men. Similarly, normal postmenopausal women had lower MSNA than men. These findings suggest that postmenopausal women continue to have a lower sympathetic nerve activity than men even after the development of EHT, and that this could have implications for genderspecific management of hypertension.

Sympathetic nerve hyperactivity and its effect in postmenopausal women

“…Our findings of greater sympathetic nerve activity in women with EHT have previously been reported [31,37]. Also, our findings of a correlation between age and MSNA indices in the four groups of the present study is consistent with published evidence in women that increased age was associated with increases of MSNA [25,38].…”

“…There have been reported data in women finding that menopause is associated with reduced femoral artery blood flow as well as increased MSNA [27], and in men finding that older age is associated with reduced femoral artery blood flow and increased MSNA [28,29]. However, the MSNA levels and their increase in hypertension in premenopausal and postmenopausal women remain lower relative to matched men [30,31]. With these considerations, it is hypothetically possible that vascular regions supplied by MSNA are subject to greater sympathetic vasoconstrictor effects following the menopause in normotensive women, and that this trend is augmented in women with EHT.…”

“…None had evidence of secondary hypertension, left ventricular hypertrophy, peripheral vascular disease, metabolic syndrome, arrhythmia, neuropathy, or chronic disease that may influence the autonomic nervous system. Seven premenopausal women with and seven without hypertension have been included in previously reported studies [30,31]. In a previous study, it was found that about 16 matched patients are needed to detect a group difference in sympathetic nerve activity of 15% with a power of 0.95 at the 5% level [4].…”

The role of cardiac autonomic function in hypertension and cardiovascular disease

“…Using microneurography to directly quantify the resting mean frequency of muscle sympathetic nerve activity, Hogarth et al [51] recently found a lower level of central sympathetic activity in a group of hypertensive postmenopausal women than in a group of age-matched men. The impact of HR in promoting the development of hypertension, atherosclerosis, and cardiovascular morbidity appears to differ between the sexes.…”

Knowing does not imply understanding

“…Possibly of greater importance, a significant sex difference persisting through menopause was seen as well. 6,7 These findings provided a platform for further investigation at the micro level.…”