A 65-year-old American woman has a 16% chance of developing Alzheimer’s. Alzheimer’s odds of a man at that same age are 9%. This blatantly unfair statistic means that nearly two-thirds of those who suffer from Alzheimer’s disease (AD) in the US are women.
For decades, scientists studying Alzheimer’s have accepted an intuitive, “common sense” explanation of the different rates at which men and women incur that brain and mind-destroying condition.
Alzheimer’s is generally encountered late in life. Because American women significantly outlive their male counterparts, the perceived wisdom goes something like this: Women spend more time being old than men do, so they naturally get AD more frequently. In other words, most men die before they lose their minds (despite evidence to the contrary).
Does a woman’s reproductive history affect her risk for Alzheimer’s?
Several new studies were introduced at the recent 2018 Alzheimer’s Association International Conference in Chicago. The results of this research point toward pregnancy and its associated conditions to explain why more women than men suffer from Alzheimer’s. Briefly put, all this new research collectively indicates that pregnancy, and the tsunami waves of estrogen and progesterone that ebb and flow throughout pregnancy, play a role in developing AD.
As if pregnancy wasn’t hard enough, now Alzheimer’s, too?
A reduced span of fertility (shortened by late menstruation and/or early menopause) and multiple miscarriages are each now linked to a higher risk of developing Alzheimer’s. One startling conclusion is that going through menopause prior to age 45 may increase the odds of incurring Alzheimer’s by up to 28%.
Conversely, a longer span of fertility (i.e. early menstruation and/or going through menopause later in life), and completing multiple pregnancies, each appears to help prevent or delay Alzheimer’s.
Paula Gilsanz is a staff scientist at Kaiser Permanente and a co-author of one of the new studies. She notes, “one hypothesized reason is that it is cumulative exposure to estrogen across the life course which may protect against the disease.”
Another attention grabber is the finding that each miscarriage carries with it an 8% higher risk of late-life dementia. However, Rachel Whitmer, the Kaiser study’s other author, warned against blaming miscarriages per se for causing Alzheimer’s. She pointed out that “whatever caused the miscarriages themselves could have more directly put women at risk for AD.”
The immune system lets down its guard when a woman becomes pregnant
An alternative line of inquiry at the conference was presented by a UCLA research project. It focused on 133 women between the ages of 70 and 100 who lived in southern England. Half had Alzheimer’s. This study, like the Kaiser research, seems to indicate that the more time women spend being pregnant, the less risk they have of ultimately incurring AD. But the results of this study go even further.
More immunity against Alzheimer’s is acquired during the first trimester of pregnancy than during the last trimester
Here’s an explanation for this observed phenomenon. The human immune system is a marvelous defensive infrastructure. It includes an amazing array of physiological armaments, such as white cells. They stand ever alert to identify, attack, and destroy alien invaders, like germs and viruses.
When a woman’s pregnancy first begins, her internal defensive systems must necessarily lower their guard. If all those weapons stayed at full alert, they might well misidentify the fetus as an external invasive danger and attempt to destroy it before it completely takes over its host. (Many pregnant women share that very same fear.)
A woman’s autoimmune system is therefore dramatically diminished during the first trimester of pregnancy. And these changes in a woman’s immune system persist to some degree throughout the rest of her life.
So the UCLA study shows that a woman acquires more immunity against Alzheimer’s during the first trimester of a pregnancy (when the immune system lowers its guard) than she does during the third trimester (when the major estrogen surges occur). This indicates that autoimmune changes may be more responsible for preventing late-life AD than are the estrogen surges.
The fact that a diminished autoimmune system in the first trimester may later help to ward off Alzheimer’s lends credence to the theory that Alzheimer’s itself has autoimmune characteristics.
New discoveries about Alzheimer’s lead to more new questions than answers
The authors of these new studies emphasize that their conclusions are really more speculative than conclusive. Much more research is necessary before we reach anything approaching effective prevention and/or treatment of AD. But I find the results of these studies to be exciting news. Let me know what you think! Thaïs
About Dr. Thais Aliabadi
As one of the nation’s leading OB-GYNs, Dr. Thaïs Aliabadi offers the very best in gynecological and obstetric care. Together with her warm professional team, Dr. Aliabadi supports women through all phases of life. She fosters a special one-on-one relationship between patient and doctor. We invite you to establish care with Dr. Aliabadi. Please click here to make an appointment or call us at (844) 863-6700.
Read the full article at latimes.com.
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