June 29, 2023 – Women in their 50s and 60s who took hormone replacement therapy were 24% more likely to develop dementia than women who never took HRT, according to a new study.
The longer the women took HRT, the more the risk increased, topping out at a 74% increased likelihood of dementia for women who took the treatment for 12 years or more.
HRT, which involves taking supplemental estrogen and sometimes other synthetic versions of hormones, is mainly used to treat menopause symptoms such as hot flashes. Previous research has shown conflicting results on whether it is protective or harmful, and questions remain about the impacts of a person’s age when they start taking it as well as how long someone takes the treatment.
This latest study was published Wednesday in The BMJ and evaluated data for all women in Denmark ages 50 to 60 years old in the year 2000. The researchers then used national health data registries to determine whether the women developed dementia during the next 18 years. To analyze a woman’s risk, they matched the 5,589 women newly diagnosed with dementia to 55,890 other women of the same age who did not have dementia. This type of study is called a population-based study, and the large, inclusive nature of the study design is considered a strength.
The findings contradict some previous research that did not show an increased risk of cognitive problems.
A critical editorial was published alongside the study and claimed that the design of the research had too many weaknesses for the questions it sought to answer and therefore was unable to prove that taking HRT causes dementia. The editorial was written by Mayo Clinic radiology professor Kejal Kantarci, MD, and by Harvard Medical School professor of medicine JoAnn E. Manson, MD, MPH, DrPH. They suggested future study of HRT risks would be improved by longer follow-up time, randomizing whether women received HRT, and brain imaging.
In the online comment section for the editorial, a letter signed by lead researcher Nelsan Pourhadi, MD, on behalf of all study authors states that they agree their study had limitations, but that its strengths point to the possibility that HRT increases dementia risk.
“Consequently, we call for further research to investigate if the observed association is explained by a causal link, which remains uncertain, but not unlikely,” Pourhadi wrote in the comment.