Women who begin taking hormone replacement therapy (HRT) within five years of the onset of menopause may reduce their risk of developing Alzheimer's disease, a study suggests.
HGH DoctorScientists monitored 1,768 women aged 65 and over for 11 years, taking note of their history of HRT use.
During the study, 176 women developed Alzheimer's disease.
The researchers found that women who started HRT within five years of the onset of menopause had a 30% lower risk of Alzheimer's than those who had not used hormone therapy.
The threat was unchanged among HRT users who began the treatment more than five years after the start of menopause. A higher risk of dementia was seen in women who started combined estrogen and progestin therapy when they were at least 65 years old.
"This has been an area of debate because observational studies have shown a reduced risk of Alzheimer's disease with hormone therapy use, while a randomized controlled trial showed an increased risk," said study leader Dr. Peter Zandi, from Johns Hopkins University in Baltimore, US.
"Our results suggest that there may be a critical window near menopause where hormone therapy may be beneficial. On the other hand, if started later in life, hormone therapy could be associated with an increased risk of developing Alzheimer's disease."
The research is published in the latest online issue of the journal Neurology.
Dr. Victor Henderson, from Stanford University in California, who wrote an accompanying editorial, said: "More research is needed before we can make new clinical recommendations for women and their use of hormone therapy."
Dr. Simon Ridley, from Alzheimer's Research UK, said: "Previous 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 Alzheimer'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 significant for guiding future research in this area.
"Any medication may carry some potential benefits and drawbacks, and anyone concerned about hormone replacement therapy should speak to their GP."