The results of the largest study of its kind have found that the age at which menstruation begins and when menstruation stops may influence the risk of developing dementia later in life.
The analysis included health information from 273,260 female UK Biobank participants and found that, relatively speaking, those who start their periods earlier and reach menopause at an older age are more likely to This suggests that the brain is aging in a healthy manner.
Specifically, researchers at University College London found that people who menstruated for 34 to 37 years had a 28 percent lower risk of dementia than those who had a shorter “reproductive period.” did.
This correlation appears to depend both on when menstruation began and when it stopped, either naturally or through reproductive surgery.
In humans, estradiol most powerful A member of the estrogen family of hormones.that level There are ups and downs throughout life.peaks during reproductive age and declines with menopause.
Current research uses menstruation as a proxy for these hormone levels. Participants who started menstruating at age 15 or older were shown to have a 12% increased risk of dementia. Meanwhile, 24% of women experienced menopause after age 50. Diminished Dementia risk.
Hormone replacement therapy, which replaces estrogen after menopause, does not seem to affect results. This association was consistent between people with and without genetic risk factors for dementia.
“Based on the results of this study, estrogen may play a role in protecting women from developing dementia,” the UCL team said. conclusion.
If that’s true, it might help explain why over 60% of people Women are more likely to develop this neurocognitive disorder. In fact, as far as scientists know, gender is the biggest predictor of developing dementia, apart from age.
Nevertheless, the influence of sex hormones on female brain aging is poorly understood. Until now, most brain research has been conducted on male brains.
only 2 percent Only 0.5 percent of published neuroimaging studies bother to mention hormonal factors. more than half Such studies have found statistically significant associations between sex steroids and brain changes in women.
For example, researchers studied the postmortem brains of women who died of Alzheimer’s disease, the most common form of dementia. measured Estrogen levels are relatively low.
tracking animal research found that the mammalian brain, particularly areas associated with learning and memory, are highly sensitive to estrogen.Several Results for rodents Estradiol improves neural connections in the hippocampus, probably reduce Protein plaque buildup associated with Alzheimer’s disease.
However, similar studies using human brains have found contradictory results.
In 2021, study A study of 99 middle-aged women found that longer reproductive years and more years of exposure to estradiol were associated with increased amounts of gray matter in the brain. teeth reduction The amount is high in Alzheimer’s disease patients.
But in 2020; analysis Among 16,854 women, the higher their lifetime exposure to sex hormones, the more more Obvious signs of brain aging.
To shed light on these mixed results, UCL researchers carried out the largest analysis to date to their knowledge. Their findings suggest that cumulative lifetime exposure to estrogen is closely associated with healthy brain aging.
One of their more worrying findings was that people who had genital surgery had an 8% increased risk of dementia.
Thankfully, it appears that this risk may be significantly improved if the surgery is performed later in life (when patients are in their 40s or 50s rather than in their 20s or 30s).
However, the UCL authors say many of these surgeries are unnecessary and are being done too young.According to some estimates, about 90 percent A high percentage of hysterectomies are performed for benign conditions, with 54% of women in the United States who have a hysterectomy have both ovaries removed. More than a third of the women in this group were under the age of 44.
“When women undergo surgery for these benign conditions, their exposure to estrogen decreases rapidly during perimenopause, accelerating changes in the nervous system.” explain Researcher at UCL.
”[R]In clinical practice, genital surgery should be considered as an increased risk of dementia. ”
Although the current analysis provides the most robust observations to date, it can only reveal associations at the population level.
More research is needed to determine how estrogen directly affects brain aging and what can be done about it. Other sex hormones, such as progesterone, may even be affected. It plays an overlooked protective role.
Although the current study did not show improved cognitive health outcomes for people who received hormone replacement therapy, in the past some researchers have theorized It’s not just whether these treatments are given that matters for brain health, but the timing.
More research is needed to understand why women develop dementia at higher rates than men and how the risk can be reduced.
Experts say it’s essential to prioritize research into women’s brains in the future if we want to truly understand cognitive decline.
This study American Journal of Geriatric Psychiatry.
