The Women’s Health Initiative (WHI) was launched in the early 1990s to study women’s health regarding cardiovascular and other diseases, cancer, and menopausal care. When the WHI’s published its research on hormone replacement therapy (HRT) in 2002, it was the largest of its kind. And indeed, the results were groundbreaking—in the worst way possible.
The research reported that HRT increased the risk of cancer, dementia, and other diseases in menopausal women. Scientists said the risks outweighed the benefits, and with that, HRT became taboo. Even after other researchers pointed out the study’s many flaws, the stigma has persisted for decades.
Finally, 20 years later, the North American Menopause Society updated its guidelines to correct the error. Here’s what you need to know (and what you need to unlearn).
What Did The WHI Get Wrong?
Despite the WHI’s noble intentions, the results of the 2002 paper were inaccurate for several reasons.
1. Participants Were Past Menopause Age
According to a 2006 critique by Dr. James H. Clark published in Nuclear Receptor Signaling, one predominant issue was the age of the study’s participants. Of the tens of thousands of women who participated in the study, most were “12-15 years past the onset of menopause,” Clark wrote.
“Thus, these women were without their pre-menopausal levels of estrogen and progesterone long enough to bring about changes in various bodily functions, which are the precursors of disease.”
The bottom line: the women enrolled were not representative of the population of women who would typically be starting on an HRT regimen.
2. Participants Were Overwhelmingly Already At Risk
Dr. Peter Attia discusses the study on his YouTube channel, in which he calls the WHI study “the biggest screw-up of the entire medical field in the last 25 years.”
Attia explains the time constraints for the study prevented scientists from using younger women, who they would have had to follow for longer than older women to determine menopause (and HRT’s) effects on the body later in life.
But Attia says the participants weren’t just older; they were sicker, too. “Something like 30, 40 percent of these women were smokers. The prevalence of obesity, diabetes was enormous. [The researchers] disproportionately picked the most unhealthy population they could.”
3. Relative Risk Vs. Absolute Risk
Moreover, Clark argues that the WHI blew the corresponding disease incidence rates out of proportion. Rather than using absolute risks, which provide a clearer picture of a population’s overall risk level, the study emphasized relative risks.
Relative risk ratios focus on smaller groups and thus create larger risk percentages. The media latched onto these bigger (and scarier) numbers, inaccurately suggesting that the correlation between HRT and various diseases was greater than it actually was.
As Dr. Louann Brizendine explained to Suggest editor Kristen Phillpkoski, the WHI study set research in women’s hormone therapy back 20 years. “One of the things that happened is they stopped teaching [about it] in medical schools.”
“Even OBGYNs,” Brizendine continued, “many of them say they aren’t prepared to do hormone therapy for women. They didn’t get any more than one lecture during their residency in hormone therapy.”
The AARP reported that only 20% of OBGYN residency programs provide any menopausal training at all. Those who do receive about four hours of menopause training during medical school. Philip M. Sarrel, professor emeritus of gynecology at the Yale School of Medicine told AARP, “doctors are not helpful. They haven’t had training, and they’re not up to date.”
The Facts: HRT Is Safe And Effective For Most Women
Luckily, it looks like that might be starting to change. A 2022 study published in Cancer found that HRT significantly reduced all-cause mortality and cardiovascular disease when initiated in women younger than 60 and/or at or near menopause.
As Texas-based OBGYN Dr. Mary Claire Haver outlines on her YouTube channel, these findings suggest HRT can prevent or reduce the symptoms of many diseases women encounter during midlife including cardiovascular disease, osteoporosis, Alzheimer’s, and sexual and vaginal disorders.
Based on these findings, the North American Menopause Society has changed its guidelines regarding HRT. “Hormone therapy remains the most effective treatment for vasomotor symptoms [hot flashes, night sweats, etc.] and the genitourinary syndrome of menopause and has been shown to prevent bone loss and fracture,” the NAMS said.
“For women younger than 60 years or who are within 10 years of menopause onset and have no contraindications, the benefit-risk ratio is favorable for treatment of bothersome VMS and prevention of bone loss. For women who initiate hormone therapy more than 10 years from menopause onset or older than 60, the benefit-risk ratio appears less favorable because of the greater absolute risks of coronary heart disease, stroke, venous thromboembolism, and dementia.”
So, while the NAMS statement acknowledges some findings of the WHI study, it puts them in the correct context. For most women younger than 60 or near menopause onset, HRT is a safe, effective, and in some cases, life-saving treatment.
What About Breast Cancer?
While the NAMS statement suggests HRT is an effective treatment for most women, this does not mean all women. Inaccuracies of the WHI aside, there are still correlations between estrogen levels and breast or uterine cancer development.
Using estrogen and progestin (or combined hormone therapy) can reduce the risk of estrogen-related cancers. But the danger is not non-existent. As the American Cancer Society explains, “to put the risk into numbers, if 10,000 women took [HRT] for a year, it would result in up to about eight more cases of breast cancer per year than if they had not taken hormone therapy.”
The ACS also cites a clinical trial called the HABITS study that found breast cancer survivors taking HRT “were much more likely to develop a new or recurrent breast cancer than women who were not taking these hormones. Because of this, doctors generally do not recommend [HRT] if a woman was previously treated for breast cancer.”
So, What Does This Mean For You?
Regardless of the data debunked from 2002, HRT might not be for everyone. But as more accurate menopause information enters the mainstream, it’s likely that many women will discover that they are eligible for hormonal treatments (and that it could have enormous benefits on their overall well-being).
Ultimately, it’s a decision for you and your doctor to make, so it’s critical to find a doctor who observes the most up-to-date and factually accurate menopause guidelines. If you are looking for a new health provider, Dr. Haver and her team have curated a list of recommended physicians across the US, Puerto Rico, Canada, the UK, and South Africa.
Whatever route you choose in your midlife journey, let science—not fear—lead the way.