Why is it often the case that these drugs are tested only on those in the earliest stages of the disease? Since we do not know how rapidly the disease will progress in an individual until that progression is followed for a year or two, what are the researchers comparing (in the earliest stage of PD) the rate of progression to? Also, if they want to see if it can reverse PD, they need participants who have some real, measurable progression. You cannot see is someone is getting better if they are almost normal already. The drug is already on the market, so why not test it on people in various stages?

Ann