> Nearly two-thirds of Americans with Alzheimer’s disease (AD) are women, but the reasons why women are more vulnerable are still not fully understood. Scientists have long theorized that the loss of estrogen after menopause may reduce the brain’s natural protection against memory loss and neurodegeneration.

The part that makes no sense for me is men ending with smaller rates of dementia, given they had much less estrogen to begin with. Men have less incidence of dementia. Men also have much lager incidence of baldness. Did somebody already study if baldness and dementia are inversely correlated? I don't know, perhaps sunlight exposure in the scalp have neuroprotective effects?

Given the prevalence of baldness, and the downside of the condition for sexual attractiveness of its bearers, I suspect we will still discover some strong unexpected upside to explain why this trait was selected for regardless.

> baldness, and the downside of the condition for sexual attractiveness of its bearers

Just a guess, and I highly doubt there are any reliable statistics on this, but perhaps balding men are less likely to be tempted to abandon their family unit, thereby making it more likely that their children will thrive and carry on their genes?

I base this theory on my own experience, which is that I went completely bald in my early thirties and haven't had a second look from a woman ever since. Even if I were the sort to want to cheat on my wife, there wouldn't be any takers![0]

[0] I'm not claiming that bald men are necessarily sexually unattractive. I just know that it didn't work for me, looks-wise.

Men have significant estrogen:

Men: roughly 10–40 pg/mL Women (not at ovulation): roughly 30–40 pg/mL

At Ovulation, women spike. Hence, libido changes. If you know, you know.