Taking hormone replacement therapy during the menopause does not increase the risk of dementia, a major study suggests.
However, staying on such treatments long-term was found to be linked to a slight increase in Alzheimer’s, according to the Oxford University research, published in the BMJ.
Evidence about links between HRT and conditions such as Alzheimer’s disease has been conflicting. Some studies have suggested it could have a protective effect, while others have suggested it raises the risks.
The new study by the Universities of Oxford, Southampton and Nottingham published in BMJ is one of the largest, involving more than 600,000 women. It found that being on HRT for up to five years did not increase the risk of dementia.
Researchers said women should find the results reassuring, providing more clarity about the risks.
Risks of prolonged treatment
However, the study found that staying on oestrogen-progesterone therapy for five to nine years increased the risk of Alzheimer’s disease by 11 per cent, while staying on it for more than a decade increased the risk by 19 per cent.
Another less common type of HRT was associated with a lower risk of dementia.
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 a decade, with a 1.1 per cent decrease in risk for each year of treatment.
How to dementia-proof your menopause
Every year, around 1.5 million women experience troubling post-menopausal symptoms, including hot flushes, night sweats, sleep problems and emotional problems. Of those, around 150,000 are prescribed HRT, in the form of tablets, gels, creams or patches.
The medication works by boosting levels of the hormones oestrogen and progesterone, which are lower among women during the menopausal period.
Many women use the therapy for less than five years, with long-term use linked to breast and womb cancer, but medical guidelines do not set out any minimum or maximum period of use.
Around one in 10 women aged 80 and over will develop dementia.
What are the early signs of dementia?
Researchers compared 118,501 women aged 55 and older diagnosed with dementia between 1998 and 2020 with 497,416 women of the same age without the condition.
In each of the groups, 14 per cent of women used HRT for more than three years.
"This large observational study found no overall association between use of menopausal hormone therapy and risk of developing dementia," the authors concluded.
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 drug for "vasomotor symptoms", such as hot flushes and night sweats.
They said hormone therapy should not be prescribed in order to prevent dementia.
Women ‘should not be put off HRT by risks’
Dr Sara Imarisio, from Alzheimer’s Research UK, said the increased risks found for those taking HRT for five years or more was “small”, the equivalent of up to seven extra dementia cases per 10,000 person years.
“Hormone therapy provides important benefits to many women, helping to combat the symptoms that menopause can bring. Women who require hormone therapy should not be put off by these results, and anyone concerned about the effects of this treatment should speak to their doctor,” she said.
Dr Haitham Hamoda, the spokesperson for the Royal College of Obstetricians and Gynaecologists, and the chair of the British Menopause Society, said too many women were “suffering in silence” during the menopause, which could affect different women very differently.
He said: “Symptoms can vary and be extremely debilitating, significantly impacting on their physical and psychological health, career, social life and relationships. The findings from this research should be helpful to both women and doctors.”