Summary: Sex hormones are central to brain health and help explain sex-based differences in dementia risk and other neurological conditions.
Source: AHA
Medical science has moved far beyond the old notion of “bikini medicine,” when women’s health was treated as largely limited to reproductive organs.
In recent decades researchers have documented many ways that men’s and women’s bodies respond differently to the same diseases. As awareness grew that heart disease presents differently by sex, scientists have increasingly focused on the brain—and they are finding clear sex-based differences in how the brain ages and how neurological disease develops.
“We are not talking about entirely different brains,” said Lisa Mosconi, director of the Women’s Brain Initiative at Weill Cornell Medicine in New York. “The key is that male and female brains age differently.”
Those differences matter. Women account for about two-thirds of Alzheimer’s disease diagnoses, are twice as likely to experience major depression, are three times more likely to be diagnosed with autoimmune conditions that affect the brain such as multiple sclerosis, and are four times more likely to have migraines. Women also have higher mortality from stroke.
Many factors contribute to these disparities, but sex hormones—testosterone in men and estrogen in women—play a leading role. Hormones act like conductors for many brain processes and help determine whether cognitive function is preserved or declines.
“We often think of sex hormones only in relation to reproduction,” Mosconi said. “But they are also critical for maintaining brain health.”
Estradiol, the dominant form of estrogen produced during a woman’s reproductive years, appears especially important. Dr. Kejal Kantarci, director of the Women’s Health Research Center and a radiology professor at Mayo Clinic in Rochester, Minnesota, notes that longer lifetime exposure to estradiol may provide protective benefits for the brain.
In a 2020 study published in Brain Communications, researchers observed that women with longer reproductive spans—measured from the onset of menstruation to menopause—showed slower progression of certain forms of multiple sclerosis. That study also found that a higher number of pregnancies, which temporarily raise estrogen levels, was associated with less severe disease progression.
Conversely, the abrupt decline in estradiol that accompanies menopause can coincide with measurable changes in the brain. Some of these changes may begin in midlife and only become clinically apparent decades later. Mosconi’s imaging research suggests that amyloid plaques, protein buildups associated with Alzheimer’s disease, can start accumulating during the menopausal transition even when cognitive symptoms have not yet emerged. She has also observed shrinkage in memory-related brain regions during this period.
“We rarely frame Alzheimer’s as a disease that begins in midlife,” Mosconi said. “But for many women, the biologic processes that lead to later dementia start around the time of menopause.”
Other midlife shifts linked to loss of estradiol include increased anxiety, depression and the emergence or worsening of autoimmune conditions. For women who are genetically or biologically predisposed to these disorders, the menopausal transition can act as a trigger.
Mosconi’s metabolic imaging work indicates that average brain energy production declines by roughly 20% or more during menopause, a drop not seen in men of the same age. That difference may reflect the relatively rapid and early reduction in female sex hormones compared with the slower hormonal changes men experience.
But more estrogen isn’t always better, Kantarci said. “You can’t just say estrogens are good for you. It’s not that simple.”
Timing appears to be a crucial factor. Earlier clinical trials in older postmenopausal women (age 65 and up) suggested hormone therapy could increase the risk of dementia. However, more recent work indicates that starting estrogen therapy closer to menopause—within a few years of its onset—may offer cognitive protection. Observational data also link longer natural exposure to estrogen with better cognitive outcomes later in life.
Kantarci’s research supports the idea of a “critical window” around the menopausal transition. In her studies, women who received estradiol via a patch in their 50s showed reduced brain shrinkage years later, particularly in frontal brain regions involved in decision-making and attention, compared with women given placebo.
Her team is continuing to follow participants to determine whether hormone therapy during the menopausal transition produces lasting cognitive benefits or risks.
At the same time, experts caution that hormones are only part of the picture. Social and life-course factors—women’s longer lifespans, their greater likelihood to serve as caregivers, and higher rates of certain mental health conditions—also influence cognitive risk. “Caregiving and the stresses it brings may compound biological vulnerability,” Kantarci noted. “The issue is multifaceted and circular: biology, social roles and health all interact.”
Understanding how sex hormones shape brain aging could improve prevention strategies and timing for interventions. Recognizing midlife as a pivotal period for women’s brain health may help clinicians and patients make more informed decisions about monitoring, lifestyle changes and, where appropriate, hormone therapies tailored to individual risk profiles.
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Source: AHA
Contact: Press Office – AHA
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