.... is a "group" of people, somewhere on this planet that live relatively stress free, and are "proven" relatively stress free, I dunno, maybe an ethnic group or a subset of wealthy people or some group of people (i can't really see who would qualify as life is tough for just about everybody, imho), and the occurrence of PD determined in this group and compared to a "very stressed" group of people. THis would be interesting.
BTW- I guess you have to be a horse to get a stem cell cure these days , did ya'll see that in the news?