Drugs commonly given to menopausal women are not linked to an increased risk of developing dementia, a study suggests.
Hormone replacement therapy treatments are prescribed to relieve symptoms of menopause such as hot flushes, night sweats and mood swings.
The medication works by replacing the hormones that are lower in women during menopause.
A small number of previous studies have had inconsistent findings when it comes to HRT use and dementia.
Some laboratory studies and small trials have suggested there might be a beneficial use HRT to stem “age-related brain decline”, while another study linked a certain type of hormone therapy to an increased risk of Alzheimer’s.
Researchers from the universities of Nottingham, Oxford and Southampton set out to conduct a large trial involving more than 118,000 women aged 55 and over who had dementia diagnosed between 1998 and 2020.
Their information, drawn from UK GP surgery data, was compared to almost half a million women who did not have dementia.
In each of the groups, 14 per cent of women used HRT for more than three years.
Overall, no increased risks of developing dementia associated with menopausal hormone therapy were seen, the authors said.
But there were different findings among some sub-groups within the study.
Long-term users of a specific treatment were found to have a “slightly” increased risk of developing Alzheimer’s, according to the study, published in the BMJ.
Women taking oestrogen-progestogen therapy for between five and nine years had an 11 per cent increased risk, and those taking the medication for more than a decade were deemed to have 19 per cent more risk.
But oestrogen-only therapy was linked to 15 per cent decreased odds of dementia overall among women younger than 80 who received treatment for at least 10 years, with a 1.1 per cent decrease in risk for each year of treatment.
“This large observational study found no overall association between use of menopausal hormone therapy and risk of developing dementia,” the authors said.
“This finding was consistent across different types of hormones, doses, applications, and time of hormone therapy initiation.
“We found a decreased risk of dementia for cases and controls younger than 80 years at diagnosis who had been taking oestrogen-only therapy for 10 years or more.
“A subgroup analysis of cases with a diagnosis of Alzheimer’s disease showed a small increase in risk associated with oestrogen-progestogen therapy.
"This rose with each year of exposure, reaching average risk increase of 11 per cent for between five and nine years of use and 19 per cent for 10 years or more.”
In a linked opinion piece, Prof Pauline Maki, from the University of Illinois, and Prof JoAnn Manson, from Harvard Medical School, said the study should provide reassurance for women prescribed the therapy for “vasomotor symptoms”, namely hot flushes and night sweats.
“An improved understanding of the risks and benefits of hormone therapy is needed to promote evidence-based management of menopausal symptoms in women,” they wrote.
“Overall, these observations do not change the recommendation that menopausal hormone therapy should not be used to prevent dementia.
"At the same time, it is helpful for providers to put dementia findings in context for patients.
“The primary indication for hormone therapy continues to be the treatment of vasomotor symptoms, and the current study should provide reassurance for women and their providers when treatment is prescribed for that reason.”