[1] Inst Salud Carlos III, Natl Ctr Epidemiol, Area Epidemiol Aplicada, Dept Appl Epidemiol, Madrid 28029, Spain
[2] Univ Barcelona, Parkinsons Dis & Movement Disorders Unit, Dept Neurol, Inst Clin Malalties Sistema Nervios,Hosp Clin, Barcelona, Spain
[3] Univ Barcelona, Parkinsons Dis & Movement Disorders Unit, Dept Neurosurg, Inst Clin Malalties Sistema Nervios,Hosp Clin, Barcelona, Spain