Summary: Longer reproductive periods—used as an indicator of prolonged exposure to a woman’s own estrogen—were associated with higher levels of Alzheimer’s disease biomarkers in cerebrospinal fluid in a long-term observational study.
Source: NAMS
Background: Estrogen has long been investigated for its potential influence on a woman’s risk of developing Alzheimer’s disease (AD). Rather than measuring circulating hormone levels at a single time point, researchers in this study examined reproductive lifespan—the interval between menarche and natural menopause—as a practical marker of lifetime endogenous estrogen exposure, and evaluated its relationship to cerebrospinal fluid (CSF) markers linked to preclinical AD.
The study’s findings are published in the journal Menopause.
Alzheimer’s disease accounts for roughly 60% to 70% of all dementia diagnoses, making it the most common form of dementia. Approximately two-thirds of people diagnosed with AD are women. While greater longevity in women partly explains this disparity—age is the strongest known risk factor for AD—researchers continue to explore biological and reproductive factors that may contribute to sex differences in disease risk.
Previous investigations into estrogen and cognitive decline have produced mixed results. Some studies have reported links between both higher and lower blood estradiol levels and dementia risk, while others found no clear association. Research on menopausal hormone therapy has likewise shown conflicting outcomes, with some reports suggesting increased dementia risk and others suggesting protection. Associations between shorter or longer reproductive periods and cognitive decline have also been inconsistent.
Despite the volume of prior work, relatively few studies have evaluated whether indicators of lifetime estrogen exposure correspond to established AD biomarkers measured directly in cerebrospinal fluid—the clear fluid that bathes the brain and spinal cord and can reflect early pathological changes associated with Alzheimer’s disease. To address this gap, investigators followed a small cohort of women who experienced natural menopause and were free of dementia, tracking them for 25 years and ultimately analyzing CSF samples for AD-related biomarker profiles.
Key findings: In this long-term, population-based sample, a longer reproductive period—serving as a surrogate for extended endogenous estrogen exposure—was associated with increased levels of cerebrospinal fluid biomarkers that are commonly linked to preclinical Alzheimer’s disease. These biomarker changes appeared in women who did not have clinical dementia, suggesting that reproductive lifespan may relate to early, preclinical biological changes associated with AD.
Interpretation and caveats: The authors emphasize that this was a relatively small study and that its findings should be interpreted with caution. While the observed association suggests a potential link between duration of endogenous estrogen exposure and preclinical CSF markers of Alzheimer’s disease, the directionality and underlying mechanisms remain unclear. The results do not establish causation, and the researchers call for larger, more diverse studies to confirm and extend these observations.
Clinical relevance: If confirmed in larger cohorts, the association between reproductive lifespan and CSF biomarkers could provide additional insight into why women carry a disproportionate share of the AD burden and help refine how reproductive history is considered in risk assessments. However, decisions about hormone therapy or other interventions should continue to rely on established clinical guidance and individualized discussions between patients and their healthcare providers.
The full study is titled “Reproductive period and preclinical cerebrospinal fluid markers for Alzheimer disease: a 25-year study.”
“This small population-based study found an association between the duration of reproductive life span—a surrogate marker for exposure to endogenous estrogen—and cerebrospinal fluid biomarkers of Alzheimer disease in women without dementia,” says Dr. Stephanie Faubion, medical director of NAMS. “Although these findings need confirmation in larger studies, they may represent one piece of the broader explanation for the greater AD burden observed in women, which also relates to differences in longevity and aging patterns between sexes.”
About this Alzheimer’s disease research news
Source: NAMS
Contact: Eileen Petridis – NAMS
Image: The image is in the public domain
Original Research: The findings will be published in Menopause