Estrogen Use Linked to Increased Dementia Risks: Study

Researchers called for more studies to explore whether there is a causal link between side effects of hormone replacement therapy and dementia.

Women taking estrogen-only hormone replacement therapy (HRT) during menopause face a higher risk of suffering from dementia later in life, according to the findings of a new study.

In a report published this month in the Journal of the American Medical Association (JAMA), researchers warn that women are nearly 50% more likely to develop dementia later in life after using estrogen-only therapy, specifically estradiol, the synthetic version of estrogen.

Women in menopause are often prescribed hormone therapies, like estradiol and progesterone, to help alleviate symptoms of menopause. Symptoms can range from hot flashes, fatigue, osteoporosis, vaginal dryness, night sweats, and decreased muscle mass.

HRT Dementia Risks

In this latest study, researchers set out to determine if the findings of an older study, indicating estrogen therapy increased a woman’s risk of dementia, were relevant in modern clinical settings when hormone therapy is given under specific conditions, including initiating the therapy near menopause and for short durations to help with vasomotor symptoms, also known as hot flashes and night sweats.

Danish researchers conducted a case-controlled study that included data on nearly 30,000 women from the National Danish registers, and focused on women who had a hysterectomy and received hormone therapy from 1995 to 2018. The average age at hysterectomy was 43 years old. A total of 541 women who developed dementia were matched with 2,700 control participants.

According to the findings, estrogen-only therapy, compared to never using hormone therapy, increased a person’s risk of dementia by 49% if they used hormone therapy for 5 years or less. If they used hormone therapy for more than 5 years, their risk increased to 62%.

Taking a higher estradiol dose also increased a person’s risk of dementia, researchers determined. Using oral estradiol formulations increased the risk by 62%, whereas using a transdermal version, or the estrogen skin patch, increased the risk by 39%.

Among estrogen-only users, 94% of participants were using estradiol. Most of them, 81%, took oral estradiol compared to 19% of users who used transdermal patches.

“Estrogen-only use was associated with increased dementia rate even in women exposed near menopause, confirming findings from the large randomized clinical trial, but in a more contemporary population reflecting actual use,” the researchers concluded.

However, they said more studies are needed to determine if there is a causal relationship between hormone therapy and dementia later in life, or if it simply highlights a predisposition among women needing therapy.