The thing about the "healthy" is it really implies a value judgment. The fact is they haven't been diagnosed - yet - with PD, but healthy is really in the eye of the beholder in many ways.

I do like the "Parkinsonism" - it is more correct philosophically - but then on the other hand the first set of people may have actually received the classification of "Parkinson's " from somebody, so that did in fact happen.