Our knowledge regarding the benefits and risks of systemic menopausal hormone therapy (HT) has continued to evolve since the 2002 publication of the initial findings of the Women’s Health Initiative (WHI). In late 2017, the US Preventive Services Task Force (USPSTF) issued its recommendation against the use of menopausal HT for the prevention of chronic conditions. In this Menopause Update, Dr. JoAnn Manson, Dr. JoAnn Pinkerton, and I detail why we do not support the Task Force’s recommendation. In a sidebar discussion, Dr. Manson also reviews the results of 2 WHI HT trials, published in September 2017, that analyzed mortality in trial participants over an 18-year follow-up.
In addition, I summarize an observational study that assessed the association of HT and Alzheimer disease (AD) as well as a clinical trial that compared the impact of oral versus transdermal estrogen on sexuality in recently menopausal women.
What's the impact of long-term use of systemic HT on Alzheimer disease risk?
Imtiaz B, Tuppurainen M, Rikkonen T, et al. Postmenopausal hormone therapy and Alzheimer disease: a prospective cohort study. Neurology. 2017;88(11):1062-1068.
Data from the WHI HT randomized trials have clarified that initiation of oral HT among women aged 65 and older increases the risk of cognitive decline. By contrast, an analysis of younger WHI participants found that oral HT had no impact on cognitive function. Recently, Imtiaz and colleagues conducted a prospective cohort study of postmenopausal HT and AD in women residing in a Finnish county, with 25 years of follow-up. A diagnosis of AD was based on administrative health records and use of medications prescribed specifically to treat dementia. Use of systemic HT was identified via self-report. Overall, among more than 8,000 women followed, 227 cases of AD (mean age, 72 years) were identified.
In an analysis that controlled for factors including age, body mass index, alcohol use, smoking, physical activity, occupation status, and parity, up to 5 years of HT use was not associated with a risk of being diagnosed with AD. Five to 10 years of HT use was associated with a hazard ratio (HR) of 0.89, an 11% risk reduction that did not achieve statistical significance. By contrast, more than 10 years' use of systemic HT was associated with an HR of 0.53, a statistically significant 47% reduction in risk of AD.1
Other studies found conflicting results
Three large randomized trials found that HT initiated early in menopause and continued for less than 7 years had no impact on cognitive function.2-4 The Cache County (Utah) long-term prospective cohort study, however, found that HT started early in menopause and continued for 10 years or longer was associated with a significant reduction in risk of AD.5
Of note are results from the 2017 report of 18-year cumulative mortality among WHI participants (see the box on page 30). In that study, mortality from AD and other dementia was lower among participants who were randomly assigned to treatment with estrogen alone versus placebo (HR, 0.74; 95% confidence interval [CI], 0.59-0.94). With estrogen-progestin therapy, the HR was 0.93 (95% CI, 0.77-1.11), and the pooled HR for the 2 trials was 0.85 (95% CI, 0.74-0.98).6
The North American Menopause Society (NAMS) HT position statement recommends that prevention of dementia should not be considered an indication for HT use since definitive data are not available.7 The statement indicates also that estrogen therapy may have positive cognitive benefits when initiated immediately after early surgical menopause and taken until the average age of menopause to prevent health risks seen with early loss of hormones.
Definitive data from long-term randomized clinical trials are not likely to become available. Observational trials continue to have methodologic issues, such as "healthy user bias," but the studies are reassuring that initiating HT close to menopause does not increase the risk of dementia. The long-term Finnish study by Imtiaz and colleagues and the Cache County study provide tentative observational data support for a "critical window" hypothesis, leaving open the possibility that initiating systemic HT soon after menopause onset and continuing it long term may reduce the risk of AD. Discussion is needed on individual patient characteristics, potential benefits and risks, and ongoing assessment over time.