Taking HRT for just a year may raise risk of dementia, warns shock study
Taking hormone replacement therapy (HRT) for just one year may increase your risk of dementia and Alzheimer’s disease, a study suggests.
According to a study of more than 60,000 Danish women, those using HRT were almost a quarter more likely to get the disease later in life.
The odds increased the longer women took the medication to treat menopausal symptoms, including hot flashes, night sweats, mood swings and decreased sex drive.
But experts stressed that the findings were observational, meaning there may also be other factors behind these women’s higher risks.
The topic is controversial and the scientific community is divided on whether HRT can increase one’s chances of developing dementia or actually improve brain health.
Those using HRT were almost a quarter more likely to get the disease later in life, according to a study of over 60,000 Danish women
Reasons for the apparently contradictory findings may be related to the age at which HRT is given, differences in the way HRT is used and different types of HRT used by a person.
To try to fill these knowledge gaps, researchers in Denmark looked at the use of combined estrogen and progestogen therapy (synthetic progestogen) and the development of dementia according to hormone treatment type, duration of use and age of the user.
They identified 5,589 cases of dementia, at an average age of 70, in addition to another 55,890 women of the same age, who did not have dementia between 2000 and 2018, for comparison.
About 1,782 (32 percent) of those diagnosed with dementia received estrogen-progestogen treatment from about age 53 for 3.8 years.
This compared with 16,154 (29 per cent) in the control group, who typically used HRT for 3.6 years.
When other factors such as education, income, high blood pressure, diabetes and thyroid disease were taken into account, women using HRT were 24 percent more likely to develop dementia and Alzheimer’s disease.
This was true even for women treated at age 55 or younger, according to findings published in the BMJ.
The risk increased the longer someone took HRT – starting at 21 percent after 12 months to 74 percent after 12 years or more.
Both daily HRT and another form taken 10-14 days a month were found to have similar results, although the study was unable to distinguish between tablets and other ways of taking hormone therapy, such as patches.
But both progestin-only therapy and vaginal estrogen did not have a higher link with dementia, they found.
The researchers from the University of Copenhagen and the Danish Dementia Research Center were unable to isolate vascular dementia from other forms of dementia, which could provide more insight.
They recognized that women using HRT may already be predisposed to vasomotor symptoms of menopause – such as hot flashes and night sweats – and dementia.
As such, they conclude: ‘Further studies are warranted to determine whether these findings represent a true effect of hormone therapy in menopause on dementia risk, or whether they reflect an underlying predisposition in women who require these treatments.’
Experts from Harvard and the Mayo Clinic in the US said that while there were strengths to the study – including its large size, good data and varied treatments – this type of observational study cannot replace clinical trials.
In a linked editorial they write ‘confounding factors may produce a false signal for a higher risk of dementia in younger women taking hormone therapy for short or long duration’.
“These findings cannot inform shared decision-making about the use of hormone therapy for menopausal symptoms.
Dr. Susan Kohlhaas, from Alzheimer’s Research UK, said understanding whether HRT plays a role in dementia risk has been a priority for the research community, but the findings so far have been ‘inconclusive and contradictory’.
She said: ‘This large, nationwide Danish study has found a link between both short-term and long-term use of HRT and an increased risk of dementia.
“Unfortunately, it’s inconclusive about whether HRT contributes to the risk of dementia, because the study didn’t take into account some of the other known factors, such as social isolation, smoking, or dietary factors like alcohol.”
‘Women need to understand the implications of the decision to take HRT in terms of benefits and risks, and as far as dementia is concerned, at this point we will have to wait for more research to provide clearer answers.
“In the meantime, people should talk to a qualified health care professional if they want to learn more about the known benefits and risks of taking HRT to manage menopausal symptoms.”
In the accompanying editorial, the US researchers said that women with brain fog, hot flashes and sleep disturbances are more likely to seek hormone therapy than those who do not experience these symptoms.
During the early years of this research, hormone treatment was also seen as a strategy to slow cognitive decline and was even prescribed for that purpose.
These women who were prescribed HRT might stay in the health system longer and therefore be more likely to be diagnosed with dementia than women who were left untreated and did not seek medical attention, they said.
Doctors were keen to emphasize that HRT is an effective and safe treatment for most women with menopausal symptoms, adding that any associated risk is ‘small’.
Dr. Anita McGrogan, from the University of Bath, noted that the study was conducted in Denmark, where prescribing practices may be different, adding that more information is needed before these findings are generalized to other populations.
She said other risk factors for dementia – such as smoking, physical activity, obesity – have not been addressed.
She said: ‘Prescribing and availability of HRT in Denmark may be different than in other countries, such as the UK, where we know that prescribing and access to HRT differs and may be related to the ability to seek it out and pay for the treatment.
‘In the paper, those on long-term HRT may have different reasons for this than those on short-term HRT (and a different risk of dementia); similarly, people with more health problems may have greater access to health care providers and the symptoms of dementia may be identified and investigated earlier.’
Dr. Sarah-Naomi James, of Lifelong Health and Aging at University College London, said the study has both “strong” and “fundamental limitations” for such a complex issue.
She said: ‘Sleep or mood changes are common symptoms of menopause and reasons to seek HRT; meanwhile, we are beginning to understand that sleep and mood may play an important role in the manifestation and progression of dementia.
“The best way to understand whether HRT medication itself causes dementia comes from clinical trials, and to date there is not enough evidence to support a direct link to the medication itself, and this new study alone would not support practice.” have to change.’