title: Cognition in non-demented Parkinson's disease vs essential tremor: A population-based study.
abstract: OBJECTIVE
  Patients with Parkinson's disease (PD) and essential tremor (ET) have a higher risk of cognitive impairment than age-matched controls. Only a few small studies (11-18 subjects per group) have directly compared the cognitive profile of these conditions. Our aim was to compare the cognitive profile of patients with these two conditions to each other and to healthy individuals in a population-based study of non-demented participants.
  
  
  METHODS
  This investigation was part of the NEDICES study, a survey of the elderly in which 2438 dementia-free participants underwent a short neuropsychological battery. We used nonparametric techniques to evaluate whether there are differences and/or a gradient of impairment across the groups (PD, ET, and controls). Also, we performed a head-to-head comparison of ET and PD, adjusting for age and education.
  
  
  RESULTS
  Patients with PD (N=46) and ET (N=180) had poorer cognition than controls (N=2212). An impaired gradient of performance was evident. PD scored lower than ET, and then each of these lower than controls, in memory (P<.05) and verbal fluency (P<.001) tasks. When we compared PD and ET, the former had lower scores in verbal fluency (P<.05), whereas the later had a poorer cognitive processing speed (P<.05).
  
  
  CONCLUSIONS
  This large population-based study demonstrates that both conditions influence cognitive performance, that a continuum exists from normal controls to ET to PD (most severe), and that although deficits are in many of the same cognitive domains, the affected cognitive domains do not overlap completely.
authors.affiliation: The Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, MA, USA.|Department of Neurology, University Hospital "12 de Octubre", Madrid, Spain.|Department of Medicine, Faculty of Medicine, Complutense University, Madrid, Spain.|Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Madrid, Spain.|Centro Integral en Neurociencias HM CINAC, HM Hospitales, Madrid, Spain.
authors.forename: Á
authors.identifier: http://orcid.org/0000-0003-2461-2485
authors.initials: Á
authors.lastname: Sánchez-Ferro
authors.affiliation: Department of Neurology, University Hospital "12 de Octubre", Madrid, Spain.|Department of Medicine, Faculty of Medicine, Complutense University, Madrid, Spain.|Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Madrid, Spain.
authors.forename: J
authors.initials: J
authors.lastname: Benito-León
authors.affiliation: Department of Neurology, Yale School of Medicine, Yale University, New Haven, CT, USA.|Department of Chronic Disease Epidemiology, Yale School of Medicine, New Haven, CT, USA.|Center for Neuroepidemiology and Clinical Neurological Research, Yale School of Medicine, New Haven, CT, USA.
authors.forename: E D
authors.initials: ED
authors.lastname: Louis
authors.affiliation: Department of Basic Psychology, Psychobiology and Methodology of Behavioral Science, University of Salamanca, Salamanca, Spain.
authors.forename: I
authors.initials: I
authors.lastname: Contador
authors.affiliation: Department of Neurology, University Hospital "12 de Octubre", Madrid, Spain.|Department of Medicine, Faculty of Medicine, Complutense University, Madrid, Spain.|Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Madrid, Spain.
authors.forename: J
authors.initials: J
authors.lastname: Hernández-Gallego
authors.affiliation: Department of Neurology, University Hospital "12 de Octubre", Madrid, Spain.
authors.forename: V
authors.initials: V
authors.lastname: Puertas-Martín
authors.affiliation: Department of Neurology, University Hospital "12 de Octubre", Madrid, Spain.|Department of Medicine, Faculty of Medicine, Complutense University, Madrid, Spain.|Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Madrid, Spain.
authors.forename: F
authors.initials: F
authors.lastname: Bermejo-Pareja
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D003071:Cognition / Q000502:physiology*; D060825:Cognitive Dysfunction / Q000150:complications / Q000523:psychology*; D020329:Essential Tremor / Q000150:complications / Q000523:psychology*; D005260:Female; D006801:Humans; D008297:Male; D008568:Memory / Q000502:physiology; D008875:Middle Aged; D009483:Neuropsychological Tests; D010300:Parkinson Disease / Q000150:complications / Q000523:psychology*
keywords: epidemiology; movement disorders; neurobehavioral manifestations; neuropsychological profile; neuropsychology