Why hasn't natural selection eliminated Alzheimer's?
The Alzheimer's Disease-Associated Amyloid beta-Protein Is an Antimicrobial Peptide
[See comment below for an earlier paper making this suggestion.]
Life-long protection against brain infections, in exchange for increased risk of dementia at an age few of our ancestors reached? Sounds like a reasonable tradeoff to me. Except that now we may have better options:
"it raises the possibility of preventing amyloidosis from initiating by pre-emptive targeting of pathogens/insults that stimulate the brain's innate immune system."
All we need is a good noninvasive way to detect brain infections early, so we can treat them with nonAlzheimer's-inducing antibiotics before amyloid beta-protein gets into the act.