For decades, the dominant story has gone something like this: Alzheimer’s is genetic, inevitable, and mostly out of our hands until the brain is already in trouble. That story has encouraged a kind of clinical shrug. And it hasn’t served patients, families, or society particularly well.

1. Melatonin Melatonin isn’t just the “sleep” hormone; it’s also an ancient molecule which acts as a potent antioxidant in the human...