A study has raised a question that many women would understandably want answered: could hormone replacement therapy (HRT) protect against dementia? The research found that women who had used HRT were less likely to receive a dementia diagnosis during follow-up, particularly if they had undergone surgery involving their reproductive organs. But the results do not establish that HRT caused the difference.
The researchers analysed data from 183,450 postmenopausal women in the UK Biobank, followed for an average of 13.3 years. During that period, 3,948 received a dementia diagnosis, including 1,993 diagnosed with Alzheimer’s disease.
Women who reported using HRT for at least a year, or who were still taking it when they joined the study, had a 10% lower relative risk of dementia than non-users after researchers accounted for factors including age, education, smoking, deprivation, blood pressure and diabetes.
The difference was larger among women the researchers classified as having had “surgical menopause”, meaning surgery involving removal of the womb or ovaries. HRT use was associated with a 26% lower relative risk of dementia in this group. There was no statistically clear association among women who had undergone natural menopause.
However, the surgical group included both women who had undergone a hysterectomy, which removes the womb, and women whose ovaries had been removed. Removing both ovaries causes an abrupt fall in oestrogen, while removing the womb alone does not necessarily affect hormone production in the same way. Grouping these women together makes it harder to determine whether HRT protects against dementia after a sudden loss of oestrogen.
Why the findings need care
Women who take HRT may differ from those who do not in ways that also affect dementia risk. Education, income, general health and access to care can influence both the decision to seek treatment and later health. Researchers can adjust for measurable differences, but observational studies cannot account for everything.
An early study found that women who later chose to take HRT were already healthier and at lower risk of dementia eight years before starting treatment. They tended to have more education, lower blood pressure and diabetes risk, were more active and were less likely to be overweight. These factors are themselves associated with dementia risk.
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The full article is available on The Conversation here.