Women taking HRT are more likely to be diagnosed with dementia.
Those using the drug containing both oestrogen and progestin hormones were 24% more likely to go on to be diagnosed with the debilitating condition.
Use of progestin-only and oestrogen-only forms of HRT was not associated with any increased risk. Scientists insist the worrying finding among 60,000 Danish women aged 50 to 60 does not prove HRT increases the risk of dementia but say this now requires additional research.
Some experts suspect this may be because women suffering memory problems caused by dementia are more likely to be prescribed HRT in the years before their diagnosis.
Lead author Nelsan Pourhadi, of Copenhagen University Hospital, said: “Further studies are warranted to determine whether these findings represent an actual effect of menopausal HRT on dementia risk, or whether they reflect an underlying predisposition in women in need of these treatments.”
The dementia risk appeared to increase the longer a woman took progestin-oestrogen HRT, at 21% for one year or fewer, to 74% for more than 12 years of use.
The background risk of dementia in women who did not receive HRT was 10% and the risk in those who did have it was about 12.5%.
Dr Amanda Heslegrave, of the UK Dementia Research Institute, said: “This research may cause alarm for women taking HRT, but it highlights just how much we still don’t know about the effects of hormones on women’s brain health.”
