Can I take it that Alzheimers is practically unheard of in India and other countries where curry is consumed in great quantities?
Not necessarily. The beneficial chemicals aren't easily absorbed by the body.
Not unheard of but apparently much muted:
"ScienceDaily (Jan. 13, 2005) — A dietary staple of India, where Alzheimer's disease rates are reportedly among the world's lowest, holds potential as a weapon in the fight against the disease.
The new UCLA-Veterans Affairs study involving genetically altered mice suggests that curcumin, the yellow pigment in curry spice, inhibits the accumulation of destructive beta amyloids in the brains of Alzheimer's patients and also breaks up existing plaques."
http://www.sciencedaily.com/releases/2005/01/050111170458.htm