HRT for treating the menopause does not increase the risk of dementia for most women, a study says.
Experts said the findings should be reassuring to women that HRT is safe for relief of hot flushes and other symptoms.
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HRT works by replacing the hormones that deplete during the menopause, including oestrogen, progesterone and testosterone.
Some smaller studies have suggested there might be a beneficial use for the drug to stem “age related brain decline”.
But another Finnish study linked some types of HRT to an increased risk of Alzheimer’s – the most common form of dementia.
Researchers have been able to answer this question with the support of nearly a million women.
Researchers from Oxford, Southampton, and Nottingham examined 118,000 people 55 years and older who were diagnosed with dementia during 1998 to 2020.
The data was derived from UK GP surgeries and compared to nearly half a million other women without dementia.
One in three women had used HRT for over three years.
Overall, no increased risks of developing dementia were seen in menopausal women taking HRT, The authors stated.
“This finding was consistent across different types of hormones, doses, applications, and time of hormone therapy initiation,” the authors said.
However, the types of hormones and their duration had different results.
Some women were found to have a “slightly” increased risk of developing Alzheimer’s – but only if they had been using HRT for a long time.
Women taking oestrogen-progestogen therapy for between five and nine years had an 11 per cent increased risk.
According to the BMJ study, those who have been taking the medication for over a decade were at a higher risk.
Women take a mixture of oestrogen (in the form of tablets or skin patches) and progesterone (in the form of implants, patches, and pills).
Prof Kevin McConway, Emeritus Professor of Applied Statistics at The Open University, who was not involved in the study, said the increase in risk “isn’t very large”.
He said: “We can’t even be sure that, in the case of increased risk of Alzheimer’s in women who took oestrogen-progesterone therapy for a long time, it was the therapy that caused the increased risk.
“It could have been some other factor that happens to be associated with taking that therapy.”
Dr Sara Imarisio, Head of Research at Alzheimer’s Research UK, said the “small risk” was “equivalent of up to seven extra dementia cases per 10,000 person years”.
Oestrogen-only therapy, which is usually taken only by women without a womb, appeared to be protective.
Women aged 80 and under were at a 15% lower risk of developing dementia if they had received treatment for at most 10 years.
A decrease of 1.1 percent in dementia risk was associated with each year of treatment.
An observational study can link two factors, but it cannot prove if one is the cause.
Dr. Imarisio stated: “Women who are in need of hormone therapy shouldn’t be alarmed by these results. Anybody concerned about the effect of this treatment should consult their doctor.
“Studies like this, that look for patterns in medical records can be extremely useful for identifying factors linked with Alzheimer’s risk, but they can’t tell us the root cause of that link.”
In a linked opinion piece, experts said the study should provide “reassurance” for women prescribed the drug.
Professor Pauline Maki, from the University of Illinois, and Professor JoAnn Manson, from Harvard Medical School, wrote: “An improved understanding of the risks and benefits of hormone therapy is needed to promote evidence based management of menopausal symptoms in women.”
HRT is safe and effective.
Both doctors and women hesitate to use it. This means that many women could be benefited from it.
Although the reasons for this are complex, they mostly stem from misinformation about its risks and a lack mandatory training for GPs on menopause.
Doctors say that HRT has many benefits for women younger than 60.
However, each woman will be offered a different treatment depending on her medical history, age, and family history.
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