[1] Univ Cincinnati, Dept Neurol, James J & Joan A Gardner Family Ctr Parkinsons Di, Cincinnati, OH USA
[2] Univ Iowa, Coll Publ Hlth, Dept Biostat, Iowa City, IA USA
[3] Univ Penn, Dept Neurol, Perelman Sch Med, Philadelphia, PA 19104 USA
[4] Univ Penn, Dept Psychiat, Perelman Sch Med, Philadelphia, PA 19104 USA
[5] Philadelphia VA Med Ctr, Dept Vet Affairs, Philadelphia, PA USA