At least two-thirds of Alzheimer’s patients worldwide are women. Now, a new study suggests that hormone replacement therapy (HRT) may help to prevent the disease in women who face an increased risk of developing it.

Previous research has suggested that oestrogen decline during menopause is one of the main causes of the higher prevalence of Alzheimer’s among women. This latest study focused on the APOE4 gene, which is the strongest risk factor for Alzheimer’s disease. In the UK, where the study was carried out, 25% of women are carriers of this gene.

“In addition to living longer, the reason behind the higher female prevalence (of Alzheimer’s) is thought to be related to the effects of menopause and the impact of the APOE4 genetic risk factor being greater in women. We wanted to find out whether HRT could prevent cognitive decline in at-risk APOE4 carriers,” explained lead researcher, Prof Anne-Marie Minihane, of the University of East Anglia.

The study analysed data from almost 1,200 women in 10 different European countries who had been taking part in the European Prevention of Alzheimer’s Dementia initiative – a project that aimed to streamline the testing and development of preventative treatments for Alzheimer’s disease.

The researchers specifically assessed the impact of HRT on women carrying the APOE4 gene.

“We found that HRT use is associated with better memory and larger brain volumes among at-risk APOE4 gene carriers. The associations were particularly evident when HRT was introduced early – during the transition to menopause, known as perimenopause.

“This is really important because there have been very limited drug options for Alzheimer’s disease for 20 years and there is an urgent need for new treatments,” explained Dr Rasha Saleh of the University of East Anglia.

She said that the effects of HRT in this observation study, if confirmed in an intervention trial, “would equate to a brain that is several years younger”.

According to Prof Michael Hornberger of the Unversity of East Anglia, while it is too early to say for sure that HRT reduces dementia risk in women, “our results highlight the potential importance of HRT and personalised medicine in reducing Alzheimer’s risk”.

“The next stage of this research will be to carry out an intervention trial to confirm the impact of starting HRT early on cognition and brain health. It will also be important to analyse which types of HRT are most beneficial,” he said.

This study is published in the journal Alzheimer’s Research and Therapy and can be viewed here.