When preliminary results of the Women's Health Initiative clinical trial were published in 2003, they upended menopause care in the U.S. The study linked hormone therapy — a form of treatment for menopause symptoms — with serious health conditions such as stroke, heart disease and breast cancer. As a result of the findings, hormone therapy has largely been shunned by women and doctors.
But follow-up analyses of the study a decade later found that the original conclusion was inaccurate, given that it included women who were 65 and up who already had a greater risk of heart attack, stroke, blood clots and more. It also didn't factor in the age when the women started hormone therapy and, as a result, the original study findings were considered flawed.
Last week, a new follow-up to the WHI study by the original authors was published in JAMA — and it concluded that it's safe to take hormone therapy for menopause. Here's the thing: While the researchers say that hormone therapy is safe for treating hot flashes, night sweats and other symptoms of menopause, they also say the data doesn't support using the treatment to lower the risk of heart disease, stroke or dementia — even though several other studies have found that hormone therapy can help prevent these serious conditions.
While some menopause experts are excited about the updated study results, some are disappointed by the latest conclusions. Here's why.
What did the new study find?
The follow-up analysis looked at data from more than 68,000 women enrolled in clinical trials between 1993 and 1998, following them for up to 20 years.
The researchers found that hormone therapy in the form of estrogen or a combination of estrogen and progestin had different outcomes in regard to several conditions, including heart disease, stroke, cancer and dementia.
The researchers noted that women younger than age 60 with low to average risk for cardiovascular disease and breast cancer may have more health benefits than risks in taking hormone therapy during early menopause to treat symptoms, such as hot flashes and night sweats.
"For postmenopausal women, the WHI randomized clinical trials do not support menopausal hormone therapy to prevent cardiovascular disease or other chronic diseases," the researchers concluded. "Menopausal hormone therapy is appropriate to treat bothersome vasomotor symptoms among women in early menopause, without contraindications, who are interested in taking hormone therapy." The conclusion also states that evidence from the trial "does not support routine supplementation with calcium plus vitamin D for menopausal women to prevent fractures or a low-fat diet with increased fruits, vegetables and grains to prevent breast or colorectal cancer."
Lead study author Dr. JoAnn Manson, chief of preventive medicine at Brigham and Women's Hospital, also said in a statement that "the WHI findings should never be used as a reason to deny hormone therapy to women in early menopause with bothersome menopausal symptoms," even though several menopause experts pointed out to Yahoo Life that is exactly how the findings have been used in the past. Manson also added that many women are "good candidates" for the treatment.
What are the benefits of hormone therapy beyond treating hot flashes and night sweats?
Studies conducted since the results of the original WHI trial back in 2003 have found that hormone therapy is safe and effective for women and can lower the risk of developing serious diseases beyond treating menopause symptoms such as hot flashes. For example:
- One study of more than 25,000 women between the ages of 50 and 79 found that taking hormone therapy lowered the risk of developing fractures, regardless of their previous fracture or fall history.
- A JAMA Neurology study published in 2023 analyzed brain scans from 193 women and 99 men who did not have a diagnosis of Alzheimer's or other forms of dementia. The researchers discovered that women who started hormone therapy around the time they began menopause didn't have an increased risk for developing tau proteins in the brain, which are a marker of Alzheimer’s disease.
- And another study published in 2023 found that there was a "statistically significant reduction of cardiovascular disease" by 52% after women took hormone therapy for 10 years compared to those who didn't take hormone therapy.
- A 2020 analysis of data from the WHI published in JAMA showed that women who used estrogen alone had a lower risk of breast cancer than women who received a placebo after an average of seven years of use. And a 2020 analysis published in BMJ found that there were minimal increased risks of breast cancer in people who took hormone therapy, with the lowest risk in people who used estrogen-only therapies.
- Recent research also shows that women over 65 don't have to stop hormone therapy, even though the latest WHI analysis suggests that this is just a treatment to help women get through the initial phase of menopause. The study, which was published in Menopause, the journal of the Menopause Society, analyzed data from 10 million senior women on Medicare and found that there shouldn't be a general rule for women to stop hormone therapy based on their age. The researchers also found that continuing to take hormone therapy after age 65 can be helpful for fending off symptoms of menopause.
What do menopause experts think of the latest study?
There are mixed reactions to this, with some applauding the study, and some saying the latest WHI findings don't go far enough. Others are concerned that the findings suggest there is no long-term health value in continuing to take hormone therapy, despite research showing otherwise.
"It was a rehash of old data that is now irrelevant from a study that was highly flawed," Dr. Lauren Streicher, a clinical professor of obstetrics and gynecology at Northwestern University Feinberg School of Medicine, tells Yahoo Life. "In spite of the fact that according not only to their own data, but many subsequent, better studies, with different hormones, hormone therapy decreases the risk of hip fracture, heart disease, uterine cancer, breast cancer and has a 30% decrease in overall mortality. Yet they insist inexplicably on saying that hormone therapy is only indicated to treat hot flashes."
Streicher also notes that the type of hormones used in the Women's Health Initiative study was "highly problematic, and yet, in this paper they never even mention that alternatives to medroxyprogesterone acetate [a type of progestin] such as micronized progesterone and bazedoxifene [a mixture of estrogens] have totally different safety profiles."
The conclusions and recommendations made in the new paper "contradict their own data, make no sense and are harmful to women," Streicher says.
But Dr. Kelly Casperson, a urologist and co-host of the You Are Not Broken podcast, tells Yahoo Life that she's glad the latest findings clearly state that hormone therapy is safe. She says the findings are "exciting" and "decrease fear through education." She adds, "The floodgates have opened. Watch out, doctors: They're coming in now."
However, Streicher takes issue with the implication from the study that hormone therapy should be stopped after women reach a certain age, which is something that many doctors have historically recommended for patients. She says there is "no reason" to stop hormone therapy "and many benefits to continuing it lifelong."
Women’s health expert Dr. Jessica Shepherd, an ob-gyn in Texas and author of the upcoming book on menopause Generation M, agrees. "Hormone therapy can be taken for longer periods of time than previously thought," she tells Yahoo Life.
When women stop taking hormone therapy, they can have "rapid deterioration of bone density — the thinning and weakening of the bones happens very fast," Casperson says. Women may also experience symptoms such as pain during sex and urinary tract infections, she adds.
"So many women come into my office six months after they stopped hormones and a lot of times, they don't know why they stopped — they were just told to," Casperson says.
Shepherd says it's important for women to know that hormone therapy is safe for most people to take, including during perimenopause, which is the stage before menopause. "It can be taken before actual menopause, which is crucial to longevity," she says.
Casperson encourages women to do their research about hormone therapy so that they can make informed decisions with their health care provider. You can also ask for a referral to a menopause specialist. "Really understand your health care and the decisions that are being made," she says. "This is a huge population of humans who want to feel their best. Women deserve to feel like themselves, and hormones ultimately help them feel their best."