A study by US researchers has linked hormone replacement therapy (HRT) in women to both an increased and a decreased risk of Alzheimerâ€™s disease, depending on the type of hormones used and the timing of the therapy. The study, which suggests there could be a â€˜critical windowâ€™ in which HRT may have a protective effect, is published on Wednesday 24 October in the journal Neurology online.
Previous research into the possible effects of HRT has shown mixed results, with observational studies linking it to a reduced risk of Alzheimerâ€™s, but clinical trials showing the therapy can increase the risk of the disease. The researchers set out to investigate whether the risk of Alzheimerâ€™s varied depending on the timing of hormone therapy.
The team looked at data on 1,768 women who took part in the Cache County Study, a long-term study investigating potential risk factors for dementia. Of these women, 1,105 (62.5%) had used HRT.
Analysis of the data showed that women who began HRT within five years of menopause were 30% less likely to develop Alzheimerâ€™s than those who had no HRT. However, the results also showed that after the age of 65, women who began a combined therapy of oestrogen and progestin were slightly more likely to develop the disease than those on oestrogen alone.
The researchers suggest there may be a critical window of time in which HRT may offer some protection against Alzheimerâ€™s, and argue that further research is needed to investigate this theory.
Dr Simon Ridley, Head of Research at Alzheimerâ€™s Research UK, said:
â€œPrevious research into HRT has shown mixed results, but this useful study suggests the timing of hormone use may be critical for either raising or reducing the risk of Alzheimerâ€™s. More work is needed to understand this link and help women make informed decisions about whether to start HRT, and these findings could be important for guiding future research in this area. Any medication may carry a number of potential benefits and drawbacks, and anyone who is concerned about hormone replacement therapy should speak to their GP.
â€œHalf a million people in the UK are affected by Alzheimerâ€™s disease, the most common cause of dementia, and with a rapidly ageing population that number is expected to rise dramatically. If we could delay the onset of Alzheimerâ€™s by five years we could halve the number of people who die with the disease, but for that to happen, research is crucial.â€
This material has been published with the kind permission of Alzheimer Research UK.
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