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• A new analysis is easing long-standing fears about menopause hormone therapy and dementia.
• Reviewing data from more than a million women, researchers found MHT neither raises nor lowers dementia risk.
• Experts say that decisions about hormone therapy should focus on symptom relief and quality of life, not fear of cognitive decline.

Menopause hormone therapy is not associated with an increased risk of dementia in postmenopausal women, according to new research.

Menopause hormone therapy (MHT), previously known as hormone replacement therapy (HRT), is used to manage menopause symptoms, but for decades, women have been warned about serious associated risks.

These products carried the FDA’s most stringent boxed, or “black box,” warnings, citing potential complications including cardiovascular disease, cancer, and dementia.

Evidence now suggests that some of these concerns were likely overstated.

In a major about-face, the Food and Drug Administration (FDA) removed its black box warning labels on MHT products in November of last year.

“We are returning to evidence-based medicine and giving women control over their health again,” Health and Human Services Secretary Robert F. Kennedy Jr. said in a statement.

But the strongest signal of that shift may be coming not from regulators, but from the data, or the lack thereof.

In a new meta-analysis commissioned by the World Health Organization (WHO) that included health data from more than a million women, researchers found that MHT neither increased nor decreased dementia risk. The study was recently published in The Lancet Healthy Longevity.

“The World Health Organisation currently provides no guidance on MHT and dementia risk, leaving a critical gap for women, clinicians, and policymakers. Our work will help inform upcoming WHO guidelines on reducing the risk of cognitive decline and dementia,” Melissa Melville, a PhD Candidate and Ageing Researcher in the Department of Clinical Health Psychology at the University College London and first author of the study, told Healthline.

Melville stressed that the work’s importance is twofold: for clinicians, there is an urgent need for higher-quality research; for patients, decisions about MHT should be guided by symptoms and well-established benefits and risks.

Hormone therapy’s controversial, complicated history

The history of MHT is both complex and controversial. The practice began in the 1960s and peaked in the United States in the 1990s.

However, in 2002, results from the Women’s Health Initiative (WHI), the first and only large randomized controlled trial of MHT, suggested that the risks outweighed the benefits.

Participants in the study had an increased risk of breast cancer, stroke, pulmonary embolism, and heart attack. Following the publication of these results, MHT therapy declined by 45%.

A subgroup study known as the Women’s Health Initiative Memory Study (WHIMS) later published findings on dementia and Alzheimer’s disease among women taking MHT. The study reported a substantially increased risk of dementia and overall cognitive decline.

That study alone effectively cemented the perception that MHT increased dementia risk and had a chilling effect on both patient use and subsequent research.

“A lot of other research was halted at that point, which led to only really having this study as our data point for many years. That’s what happens when a landmark paper suggests that we’re doing something potentially unsafe,” said Caroline Just, MD, program lead for women’s neurology and neuro-obstetrics at the Cleveland Clinic. Just wasn’t involved in the study.

Despite its outsized and decades-long impact on women’s health, experts say the WHI’s methodology, and even the types of hormones used, are a far cry from modern practice.

“[The WHI] is not reflective of our practice patterns now, nor the hormone therapy regimens that we use now,” said Karen Adams, MD, Farwell Family Director of the Stanford Program in Menopause & Healthy Aging at Stanford Medicine, who wasn’t involved in the research.

WHIMS remains the only randomized controlled trial to examine hormone therapy and dementia risk. Most other studies have been observational and therefore more susceptible to bias. Of the ten studies reviewed in the new meta-analysis, nine were observational.

Over the years since WHIMS was published, evidence of the association between MHT has been conflicting, with some studies also concluding that it increases the risk of dementia, while others suggest that it may be protective against cognitive decline.

The new review suggests that neither is true.

“When you put all the data together, as is common when something shows one way and other studies show the other way, the effects cancel out. So, there was no convincing difference in terms of protection or increased risk from menopause hormone therapy,” Just said.

“The depth of this review is extremely reassuring to people who prescribe menopause hormone therapy.” Just told Healthline.

Adams emphasized the limitations of current evidence.

“We just don’t have good studies,” she told Healthline, “The best thing we can say right now based on the data that we have is that hormone therapy probably does not increase the risk of dementia, but it probably doesn’t prevent it either.”

Women’s dementia risk and how to improve it

Women are disproportionately affected by dementia, even after accounting for their longer life expectancy. Almost two-thirds of Americans living with Alzheimer’s disease, the most common cause of dementia, are women.

Given that disparity, it is understandable to be concerned about ways to reduce this risk. For now, the available evidence suggests that MHT is not one of those risk factors.

The apparently neutral effects of MHT on dementia risk suggest one clear takeaway for patients: decisions about using the therapy should be guided by symptom relief and quality-of-life considerations — not fear.

“Dementia should not drive MHT decisions,” Melville said.

For women under 60 or within 10 years of their last menstrual period, there is a “window of opportunity” to start MHT, Adams said.

“To the best of our knowledge, if you start at the right time, you can continue indefinitely without significant risk,” she added.

There are also a number of well-established lifestyle habits to reduce dementia risk for women of all ages. These include:

• being active
• eating a heart-healthy diet (like the Mediterranean diet)
• not smoking
• maintaining healthy blood pressure and cholesterol
• keeping socially active
• prioritizing sleep

“Many cases of dementia are likely modifiable, meaning there’s something that the patients can do to alter or reduce their risk that is not genetic,” Just said.