Postmenopausal hormone therapy and Alzheimer's disease risk: interaction with age.
Level 4 - case-series / case-control
Case-control study assessing hormone therapy exposure and Alzheimer's disease risk
PubMed 15608005 · doi:10.1136/jnnp.2003.024927
What was done
Researchers conducted an observational case-control study examining the association between estrogen-containing hormone therapy used for more than 6 months and Alzheimer's disease risk. The study included 971 postmenopausal women (426 Alzheimer's disease patients and 545 non-demented relatives as controls). Analyses evaluated the interaction between age and hormone therapy use on Alzheimer's risk.
What was found
A significant interaction between age and hormone therapy use on Alzheimer's disease risk was observed (p = 0.03). In stratified analyses, a significant protective association was found only in the youngest age tertile (50-63 years; odds ratio = 0.35, 95% confidence interval = 0.19 to 0.66). The abstract reports no numerical risk estimates for the older age tertiles.
Why it matters
This study provides observational evidence for the timing hypothesis, suggesting that estrogen-containing hormone therapy used during early postmenopause or in younger women may reduce Alzheimer's disease risk, in contrast to randomized trial findings showing harm in older women.
Limits
The study is observational and retrospective, preventing causal inference and leaving results vulnerable to recall bias and healthy-user confounding. Using relatives as controls may introduce selection bias. Specific hormone formulations, doses, regimens, and numerical findings for older age tertiles are not reported in the abstract.
Cited by
- supports Late initiation of hormone replacement therapy may increase Alzheimer's disease risk, while early initiation may potentially only benefit women with the APOE4 allele.