[1] Cent Hosp, Dept Neurol, Bremerhaven, Germany
[2] Hosp San Pio X, ICP, Parkinson Inst, Milan, Italy
[3] Carlos III Inst Hlth, Natl Ctr Epidemiol, Area Appl Epidemiol, Madrid, Spain
[4] Carlos III Inst Hlth, CIBERNED, Madrid, Spain
[5] Kings Coll London, Natl Parkinson Fdn Ctr Excellence, London WC2R 2LS, England
[6] Inst Psychiat, London, England