Women are twice as likely as men to get Alzheimer's during their lifetime. New research sheds light on the reasons why and what you can do about it.
In pre-menopause, your brain energy is high. But in perimenopause – the transition time to menopause that generally hit in the mid to late 40’s – your brain’s ability to metabolize glucose slows down by 20-30% or more.
Your brain uses glucose as fuel to make new connections between neurons. Glucose is a type of sugar that you get from the foods you eat.
Estrogen plays a key role in this process. It regulates how your brain uses glucose as energy, and since the brain needs the energy to generate synapses between neurons, the enormous drop in estrogen levels during menopause has a distinctly negative impact on the brain. This explains why up to 60% of women transitioning to menopause experience memory problems.
But new research shows that – while these memory problems are both normal and temporary – the underlying drop in estrogen makes women’s brains more vulnerable to future damage.
Menopause does not cause Alzheimer's. It is more a window of vulnerability - especially for women with underlying risks
One reason is that because of plunging estrogen levels, the brain can’t use glucose as fuel like it used to and so it has to find new sources of energy.
One possible energy source for your brain is ketone bodies. These come from the brain’s white matter, including the myelin sheaths that protect neurons. Essentially, the brain can start to eat itself for fuel.
When estrogen levels drop, so does the brain’s ability to protect itself against toxins and infectious agents. This is because low levels of estrogen reduce the effectiveness of the blood-brain barrier, which prevents harmful substances in the blood from passing into the brain. Because the blood-brain barrier is impaired, the body responds by triggering an intense immune response to try and protect the brain from toxins and infectious agents that start slipping through. Part of this immune response includes the release of certain proteins that are believed to be behind the familiar plaques and tangles that are hallmarks of Alzheimer’s-affected brains.
All of this – reduced glucose metabolism, self-cannibalization, and long-term activation of the immune system – means that the brain of a woman in her 40s and 50s is actually aging much faster than the brain of a man of the same age…all because of plunging estrogen levels and naturally low levels of testosterone, which is believed to be neuroprotective.
So now for the obvious question: is hormone therapy the answer? Should menopausal women undergo hormone therapy to protect against Alzheimer’s? Unfortunately, the jury is still out on this. Some studies show hormone therapy protects women against dementia, other studies show hormone therapy sharply increases the risk of dementia. There are just too many variables and completely inconsistent results from study to study, to know which is the right answer.
More than 100 million women worldwide take birth-control pills, which suppress ovarian hormones, yet shockingly little is known about their long-term effects on dementia risk
What is clear, however, is that menopause and its related estrogen depletion changes the ecology of the entire body. The most important choice that women can make in the years leading to menopause is to make sure their metabolic health is in tip-top shape. Studies show that metabolic health equals cognitive health, for better or worse.
What is good metabolic health? It means having ideal levels of blood sugar, triglycerides, HDL cholesterol, blood pressure, and waist circumference…without using medications.
A big reason is that women who have poor metabolic health are generally pre-diabetic or diabetic, meaning they have reduced insulin sensitivity. Insulin-resistance compounds the risks created by plunging estrogen levels.
This is because insulin – like estrogen – is a key player in the brain’s ability to metabolize glucose. Insulin helps glucose enter brain cells for use as energy, and when brain cells become resistant to insulin, they continue to absorb glucose but fail to respond to it. This is a double whammy on the brain.
Poor or insufficient sleep – another hallmark of menopause - disrupts insulin sensitivity and therefore the brain’s housekeeping processes. This allows tau and beta-amyloid proteins to build up rather than be flushed out each night, which further disrupts insulin sensitivity, which further impairs sleep which further disrupts the brain’s housekeeping process, and so on.
Chronic stress is another big risk for menopausal women. Experiencing stressors lasting a month or more when we are in our 40s and 50s makes us more likely to have Alzheimer’s later in life.
Women take care of others; we put ourselves last. But we can't keep putting off health.
The bottom line is, menopause is a risky time for the female brain. Plunging estrogen levels kick off a chain of events that change the ecology of the entire body. The only clear evidence of how to protect yourself and your brain as you move through this transition is by maintaining good metabolic health, getting enough sleep, and effectively managing stress.
To learn more, pick up a copy of the May 2020 issue of Scientific American and read the future of medicine special report. In it, Jena Pincott offers up the latest research on the Alzheimer’s-menopause connection, some of which I have covered here today.