No Rick, there is only a limited number ie those with neurological disease who have a dysfunctional BBB. It could be a genetic failing. Then anything that worsens the permeability, eg stress, promotes further deterioration, and anything that closes the permeability slows progrssion, eg curcumin.. I have given long lists of substances which have these effects in my many BBB threads.
I still don't see why research is not done to characterise the level of BBB permeability of PWP and compare them with healthy people. The technology exists to measure it on living people. The permeability increases with age of everyone, it could be used as a diagnostic test for impending PD. There must be a threshold above which the symptons of PD occur.
Ron