Short-term and cyclical use of estrogen and progestin therapy for menopausal symptoms is linked to an increased risk of dementia, results of a large observational study show.
(AD) 20 years later, compared with those who didn’t use HT. The risk was present even in women who used HT for brief periods at menopause onset.
However, both the investigators and experts not involved in the research caution that further studies are needed to explore whether the increased risk of dementia stems from HT use or whether women in need of HT have other underlying dementia risk factors.
“We cannot guarantee that our findings illustrate a causal relationship or if they represent underlying disposition to dementia in women in need of [HT],” lead investigator Nelsan Pourhadi, MD, from the Danish Dementia Research Centre at Copenhagen University Hospital Rigshospitalet, told this news organization.
Still, he added, the findings supported evidence from the Women’s Health Initiative Memory Study (WHIMS), the largest randomized trial on menopausal hormone therapy and dementia.
The findings were published online in BMJ.
Conflicting findings
Before WHIMS was published in 2003, HT was widely prescribed to relieve menopausal symptoms. However, WHIMS, which included more than 4,000 women aged 65 years or older, revealed that HT was associated with a twofold increased risk of dementia.
Studies published since then have yielded mixed results, adding to the controversy surrounding the safety of HT.
To discover whether age of initiation or length of duration of HT affects health outcomes, Dr. Pourhadi and his team undertook the observational study.
Between 2000 and 2018, the researchers tracked more than 60,000 Danish women aged 50-60 years using diagnosis and prescription information from Denmark’s National Registry of Patients.
The registry records showed that nearly 5,600 women developed dementia and 56,000 did not develop dementia. Of the 5,600 women with dementia, 1,460 had a diagnosis of AD.
Nearly 18,000 participants in the study sample received HT – 1,790 (29%) in the dementia group and 16,150 (32%) in the control group. Half started treatment before age 53 years and half stopped within 4 years. Roughly 90% used oral medications, which included a combination of estrogen and progestin.
The median age at which participants started HT was 53 years for both cases and controls, and the median duration of use was 4 years.
Longer use equals greater risk
Compared with those who did not use HT, those who used estrogen-progestin therapy had a 24% increased risk of developing all-cause dementia (hazard ratio, 1.24; 95% confidence interval, 1.17-1.44).
The increased dementia risk was similar between continuous (estrogen and progestin taken daily) and cyclic (daily estrogen with progestin taken 10-14 days a month) treatment regimens.
Longer durations of HT use were associated with increased risk, ranging from a 21% increased risk (HR, 1.21; 95% CI, 1.09-1.35) for those who used it for 1 year or less to a 74% increased risk (HR, 1.74; 95% CI, 1.45-2.10) for use lasting 12 years or more.
Women who started HT between the age of 45 and 50 had a 26% increased risk of developing all-cause dementia (HR, 1.26; 95% CI, 1.13-1.41) while women who initiated HT between age 51 and 60 had a 21% greater risk (HR, 1.21; 95% CI, 1.12-1.29).
Progestin-only or vaginal-estrogen-only therapy was not associated with the development of dementia.
The investigators noted that because this is an observational study, “further studies are warranted to explore if the observed association in this study between menopausal hormone therapy use and increased risk of dementia illustrates a causal effect.”