Endocrine events that signal less estradiol exposure — such as shorter reproductive span, younger age at menopause and hysterectomy — appeared to increase dementia risk, study results published in Neurology showed.
"Since women are 50% more likely to develop dementia over their lifetimes than men, it's important to study any risk factors that are specific to women that could eventually lead us to potential points of intervention," Paola Gilsanz, ScD, staff scientist at Kaiser Permanente Division of Research, Oakland, California, said in a press release.
In a large diverse cohort of women followed prospectively since the 1960s, researchers examined the links between indicators of estrogen exposure from women’s reproductive period and dementia risk. Participants included women who completed health surveys and had clinical assessments reporting their age at first menstrual cycle and menopause as well as their hysterectomy status.
Gilsanz and colleagues calculated the number of reproductive years for each participant (menopause age minus menarche age) and used medical records to determine which participants developed dementia later in life. Analysis was adjusted for demographics and life course health indicators.
Of 6,137 women who provided information on age at first period, age at menopause and hysterectomy status, 42% developed dementia. Analysis indicated that women who had their first period at age 16 years or older were at 23% greater risk for dementia than those who had their first period at age 13 years (adjusted HR = 1.23; 95% CI, 1.01-1.5).
Women with reproductive spans of less than 34.4 years were at 20% elevated risk for dementia (HR 1.2 = 95% CI 1.08-1.32), according to the researchers. Analysis also showed that compared to the longest reproductive span (39 to 44 years), spans of 14 to 20 years were linked to a 55% higher risk for dementia (HR = 1.55; 95% CI 1.03–2.32), spans of 21 to 30 years were linked to a 26% higher risk (HR = 1.26; 95% CI 1.08-1.49) and spans of 31 to 34 years were linked to a 26% higher risk (HR = 1.26; 95% CI 1.09-1.47).
Gilsanz and colleagues found that women who went through menopause before age 47.4 years were at 19% greater dementia risk than those who went through menopause at age 47 or later (HR = 1.19; 95% CI 1.07-1.31). Hysterectomies were also associated with an 8% elevated risk for dementia (HR = 1.08; 95% CI 1.01-1.16).
"Estrogen levels can go up and down throughout a woman's lifetime," Gilsanz said in the press release. "Our results show that less exposure to estrogen over the course of a lifetime is linked to an increased risk of dementia. However, while our study was large, we did not have enough data to account for other factors that could affect estrogen levels, like pregnancies, hormone replacement therapy or birth control, so more research is needed." – by Savannah Demko
Disclosure: The authors report no relevant financial disclosures.