Endothelial function in postmenopausal women with nighttime systolic hypertension.

Cardiovascular morbidity increases with age but on average women are 10 years older than men when they develop cardiovascular disease.1 Consequently, the majority of cardiovascular events in women occur during their postmenopausal years. Cardiovascular risk is multifactorial but estrogen decline may also contribute to greater cardiovascular disease among postmenopausal women. Postmenopausal women have reduced endothelial function compared to premenopausal women2,3 and estrogen supplementation has been found to improve endothelial function in some postmenopausal women.4 These findings suggest that estrogen withdrawal associated with menopause may, in part, adversely affect vascular function. The menopausal transition is also associated with an increasing prevalence of hypertension becoming equivalent to and then surpassing that of men after 65 years of age.1 Postmenopausal women with hypertension have reduced endothelial function in comparison to postmenopausal women with normotension.5 Taken together these findings suggest that menopause and hypertension negatively affect endothelial function. Unlike menopause hypertension is a major modifiable cardiovascular risk factor. Among all blood pressure (BP) parameters, nighttime systolic blood pressure (SBP) is the most predictive of adverse cardiovascular events in both hypertensive cohorts and general populations.6-9 Interestingly, as nighttime SBP levels rise, the relationship between BP and cardiovascular risk increases more rapidly in women than men.10,11 The reasons for the prognostic significance of nighttime SBP are not completely known, but may involve impaired endothelial function. Functional changes to the endothelium are considered to emerge early in the atherosclerotic disease process.12 Endothelial function can be assessed noninvasively via ultrasound measurement of brachial artery vasodilator responses to hyperemic blood flow (flow-mediated dilation; FMD).13 Endothelial dysfunction, quantified as reduced FMD, is a predictor of cardiovascular events in general populations,14,15 cardiac and hypertensive patients,16,17 and postmenopausal women.18 Although higher office BP,19-22 home BP,19 24-hour ambulatory BP (ABP),23,24 and BP nondipping,25,26 are associated with greater endothelial dysfunction less is known regarding the relationship between nocturnal hypertension and endothelial function. There is some evidence of an inverse association between FMD and nighttime SBP in patients with hypertension or coronary heart disease.27,28 However, these previous studies included few women and no studies evaluated the relationship between nighttime SBP and FMD in postmenopausal women. Given that postmenopausal women are at higher risk of cardiovascular disease and the relationship between nighttime SBP and cardiovascular risk increases more drastically for woman than men the objectives of this study were: (1) to evaluate whether nighttime SBP was associated with endothelial function (FMD) and; (2) to evaluate the hypothesis that endothelial function in postmenopausal women with nighttime hypertension (nighttime SBP≥120mm Hg) is impaired relative to postmenopausal women with normal nighttime SBP (<120mm Hg).