Summary: Reproductive spans of less than 34 years were linked to an increased risk of developing dementia in women. In those who had hysterectomies, the associated Alzheimer’s risk was elevated by 8%.
Source: Alzheimer’s Research UK
A team of US-based researchers has found that a shorter reproductive window is associated with a higher dementia risk. They also found a higher risk of dementia in women who had undergone a hysterectomy. The findings are published in the scientific journal, Neurology.
Dr. Rosa Sancho, Head of Research from Alzheimer’s Research UK, said “Two thirds of people with dementia are women and while some of this difference is explained by women living longer, research has also implicated hormones like oestrogen. The start of periods and menopause are significant events in a woman’s life and it’s important to understand how these biological changes might affect long-term brain health.
“This large study links shorter reproductive period, and hysterectomy, to an increased dementia risk but it cannot tell us why the factors are associated.”
While researchers propose that shorter exposure to oestrogen throughout life could impact brain health, the study did not measure levels of the hormone directly or look at other factors that could influence oestrogen levels.
“Alzheimer’s Research UK is currently funding research at the University of Cambridge to further explore why women may have a greater risk of dementia than men. This research is helpful in giving greater clarity on a complex area of human biology, which has seen mixed results in previous studies.
“Alzheimer’s disease is caused by a complex mix of age, genetics and lifestyle factors – some of which are in our control to change and others aren’t. The best current evidence suggests that not smoking, only drinking within the recommended limits, staying mentally and physically active, eating a balanced diet, and keeping blood pressure and cholesterol levels in check can all help to keep our brains healthy as we age.”
Alzheimer’s Research UK
Rosa Sancho – Alzheimer’s Research UK
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Original Research: Closed access
“Reproductive period and risk of dementia in a diverse cohort of health care members”. Paola Gilsanz, Catherine Lee, Maria M. Corrada, Claudia H. Kawas, Charles P. Quesenberry, Rachel A. Whitmer. Neurology. doi:10.1212/WNL.0000000000007326
Reproductive period and risk of dementia in a diverse cohort of health care members
Objective Women have >50% greater lifetime risk of dementia than men but the role of female-specific endocrine milieu is not well-understood. This study evaluates associations between indicators of estrogen exposure from women’s reproductive period and dementia risk in a large diverse population.
Methods We evaluated 15,754 female members (29.9% nonwhite) of Kaiser Permanente with clinical examinations and health survey data from 1964 to 1973 and were members as of January 1, 1996. In midlife (mean age 51.1 years), women reported age at menarche and menopause and hysterectomy status. Reproductive span was calculated as menopause age minus menarche age. Dementia diagnoses were abstracted from January 1, 1996 to September 30, 2017 medical records (mean age at start of dementia follow-up 76.5 years). Cox proportional hazard models evaluated associations between aspects of reproductive span and dementia risk adjusting for demographics and life course health indicators.
Results Forty-two percent of women developed dementia. Compared to menarche at age 13.0 (mean menarche age), menarche at ≥16 was associated with 23% greater dementia risk (adjusted hazard ratio [HR] 1.23; 95% confidence interval [CI] 1.01–1.50) adjusting for demographics and life course health indicators. Natural menopause at age <47.4 (mean menopause age) was associated with 19% elevated dementia risk (HR 1.19; 95% CI 1.07–1.31). Reproductive spans <34.4 years (mean duration) were associated with 20% elevated dementia risk (HR 1.20; 95% CI 1.08–1.32). Hysterectomies were associated with 8% elevated dementia risk (HR 1.08; 95% CI 1.01–1.16).
Conclusion In this large prospective cohort study, endocrine events signaling less estradiol exposure (i.e., later age at menarche, younger age at menopause, shorter reproductive span, and hysterectomies) were associated with elevated risk of dementia.