Hormone replacement therapy (HRT) might help to reduce dementia risk for women, especially if they take it during the so-called “menopause transition phase”, according to a study published in the journal Alzheimer’s and Dementia.
About 65% of people with dementia are women, according to Alzheimer’s Research UK. Some think this could be because men have shorter life expectancies on average, especially as old age is the number one risk factor for the condition.
But Alzheimer’s Research UK said longer life expectancy alone doesn’t explain this disparity.
Studies have previously suggested that hormonal changes, especially menopause and perimenopause, might be contributing factors here.
HRT is often prescribed to help replace hormones lost during this life stage, thus reducing the severity of symptoms like hot flushes.
The age you start HRT might matter
In this study, researchers looked at health data from over 180,000 UK Biobank participants. Overall, older women who’d taken HRT for a year or more were 10% less likely to go on to develop dementia, and 16% less likely to develop Alzheimer’s disease, the most common form of the condition, than those who’d never taken it.
But these benefits weren’t shared equally. Those who’d gone through early menopause because they’d had their womb or both ovaries removed saw 26% less dementia risk after taking HRT than those in the same position who didn’t try the therapy.
There was also a 16-19% risk reduction among women who carried an “Alzheimer’s gene” and those who started their periods late or menopause early (so had a lower-than-average lifetime exposure to oestrogen).
Women who didn’t meet these criteria appeared to see neither much benefit in this regard nor any harm from taking HRT.
The paper also said that starting between 46 and 56 years old, or the ‘menopause transition phase’, appeared to be most strongly linked to long-term brain health benefits.
Study leader Professor Anne-Marie Minihane, from Norwich Medical School, said: “I think [this research] does add to the evidence that the benefits of HRT seem to outweigh the risks – and the importance of starting early... We found that [the] age of initiation of HRT seemed to be really important.”
Research about HRT and dementia is conflicted
Alzheimer’s Society said “it is not clear whether hormone replacement therapy (HRT) reduces dementia risk or not” – some studies found it might help, while others seemed to show it could even increase risk.
But speaking to the Science Media Centre, University College London’s Professor Aimee Spector, director of the Menopause Mind Lab, who was not involved in this study, said the results “are promising” as they analysed data from the UK Biobank using large samples.
She added: “The novelty of their findings was timing of HRT initiation, with those who started HRT between the ages of 46-56 conferring the greatest benefit. This supports the ‘window of opportunity’ hypothesis, suggesting that HRT use during the menopause transition phase, where symptoms are typically more problematic, is important.”
Still, she pointed out that those who take HRT might typically face fewer other dementia risk factors – like lower levels of education and greater poverty – than those who don’t, and agreed with the study authors that further randomised controlled trials are needed.
After all, this study only showed a correlation and not a causal relationship, meaning we can’t say for sure that HRT was definitely the cause of differing dementia risks.
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