Long term use of oral hormone therapy is associated with a slightly increased risk of Alzheimer’s disease in postmenopausal women, an observational study shows.
Writing in The BMJ the authors caution that the absolute risk is small, with 9-18 additional cases per 10,000 women aged 70 to 80 per year. However they advise that physicians inform women of the potential risk with prolonged use.
The study compared data on hormone therapy use by 84,739 postmenopausal women diagnosed with Alzheimer’s from 1999 to 2013 with the same number of postmenopausal women with no diagnosis.
Results showed that 83,688 women (98.8%) received an Alzheimer’s diagnosis at age 60 or older, while 47,239 women (55.7%) were aged over 80 at diagnosis. And 11,805 women (74.9%) had been taking hormone therapy for longer than 10 years.
In absolute terms, the researchers said nine to 18 excess diagnoses of the disease per year will be detected in 10,000 women aged 70-80 (incidence 105 per 10,000 women years in this age group), especially in those who had used hormone therapy for over 10 years.
The risk did not differ notably between users of oestrogen-only tablets (odds ratio 1.09 (95% confidence interval, 1.05 to 1.14) and users of combined oestrogen-progestogen tablets (OR 1.17 (1.13 to 1.21)). The exclusive use of vaginal oestradiol did not affect the risk of the disease (OR 0.99, 0.96, to 1.01).
“Hormone therapy users should be informed for a possible risk of the disease with prolonged use of Alzheimer’s disease, even though the absolute risk elevations are small,” the researchers concluded.
An accompanying editorial said the findings should not influence clinical decision making regarding the use of hormone therapy for symptom management.
“For women in early menopause with bothersome vasomotor symptoms, no compelling evidence exists of cognitive concern from randomised trials and instead there is reassurance about cognitive safety… concerns about longer term use of oestrogen plus progestin on cognitive outcomes remain,” the editorialists said.