Women who take hormone replacement therapy (HRT) after menopause are less likely to develop dementia, a landmark study published on Tuesday indicates.
Led by the University of Galway (UG) and drawing on data from a 77-year-old longitudinal study in the United States, the research also shows starting menopause as a younger woman is indicative of a higher risk of dementia.
The study, published in the Journal for Alzheimer’s disease, draws on data from 1,329 cognitively healthy women participating in what is described as “the world’s longest-running longitudinal cohort study”. It analysed the association between reproductive factors and brain ageing.
In the general population, women have a higher risk of dementia than men, with women accounting for almost two-thirds of people living with Alzheimer’s disease.
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The study says: “Greater exposure to oestrogen over the reproductive lifespan was associated with enhanced cognitive performance and larger brain volumes”, while “having more children, higher blood oestrogen levels and being older at the time of menopause were also associated with better cognitive test performance”.
Prof Emer McGrath, lead author and associate professor in medicine at UG, said the study’s purpose was to explore the association between reproductive and hormonal factors across a woman’s lifespan, and risk of brain ageing.
“We looked at neurocognitive and neuroimaging markers from MRI brain scans, as well as cognitive test performance, including tests of memory, reasoning skills and visuospatial skills. We also looked at the future risk of dementia in relation to these reproductive factors.
“We found that entering menopause at an earlier age appears to be associated with an increased risk of dementia, while post-menopause hormone replacement therapy appears to be associated with a lower risk of dementia.
“Although our results suggest positive cognitive benefits of greater lifetime oestrogen exposure, they do require further validation.”
The adults in this study were later participants in the Framingham Heart Study, which began in 1948 in the University of Boston, under the direction of the US National Heart, Lung, and Blood Institute. Its original and ongoing purpose was to identify the common factors or characteristics that contribute to cardiovascular disease in women, though its data has been used for other research such as this.
[ Prof Donal O’Shea: ‘I’ll be advising my girls to go on HRT’Opens in new window ]
In 1971, the study recruited the children of the original Framingham cohort, along with their spouses, to form the Framingham offspring cohort. This group was included in this study.
Prof McGrath said that despite its public health importance, our understanding of sex-related differences in Alzheimer’s disease and related dementias “significantly lags behind that in the cardiovascular field”.
“While longer life expectancy in women may explain some of the higher risk in women, factors including reproductive health and hormonal levels in women may play an important role,” she said.
