title: Clinical heterogeneity in newly diagnosed Parkinson's disease.
abstract: OBJECTIVE
  To determine clinical heterogeneity in newly diagnosed Parkinson's disease using cluster analysis and to describe the subgroups in terms of impairment, disability, perceived quality of life, and use of dopaminergic therapy.
  
  
  METHODS
  We conducted a k-means cluster analysis in a prospective hospital based cohort of 133 patients with newly diagnosed Parkinson's disease. Variables selected for the cluster analysis were age of disease onset, age at the moment of examination, rate of disease progression, levodopa responsive PD symptoms and levodopa non-responsive PD symptoms, cognition (mini-mental state examination) and emotional functioning (hospital anxiety depression scale). In addition, the homogeneous subgroups identified were clinically validated using descriptive statistics.
  
  
  RESULTS
  Cluster analysis with a two-cluster solution identified a younger and older age group. The three-cluster solution identified an intermediate group with respect to age. In both cluster solutions the older the onset group, the higher the progression rate and the level of motor impairments. The intermediate older onset group in the three cluster solution was characterized by more anxiety and depressive symptoms. Increasing age at disease onset was significantly associated with higher Hoehn and Yahr stages, level of disability and lower perceived quality of life.
  
  
  CONCLUSIONS
  We hypothesize there are three distinct subgroups in patients with newly diagnosed PD: a younger onset group, an intermediate older onset group with more anxiety and depressive symptoms and an oldest onset group with more motor impairment and higher rate of progression.
authors.affiliation: Dept. of Neurology and Clinical Neurophysiology, Academic Medical Center, Amsterdam, The Netherlands. b.post@amc.uva.nl
authors.forename: Bart
authors.initials: B
authors.lastname: Post
authors.forename: Johannes D
authors.initials: JD
authors.lastname: Speelman
authors.forename: Rob J
authors.initials: RJ
authors.lastname: de Haan
mesh_terms: D000328:Adult; D017677:Age Distribution; D017668:Age of Onset; D000368:Aged; D000369:Aged, 80 and over; D001008:Anxiety Disorders / Q000175:diagnosis* / Q000453:epidemiology; D016000:Cluster Analysis; D015331:Cohort Studies; D015897:Comorbidity; D003866:Depressive Disorder / Q000175:diagnosis* / Q000453:epidemiology; D004185:Disability Evaluation; D018450:Disease Progression; D005260:Female; D006801:Humans; D007113:Immunity, Innate; D007980:Levodopa / Q000627:therapeutic use; D008297:Male; D008875:Middle Aged; D009069:Movement Disorders / Q000175:diagnosis* / Q000453:epidemiology / Q000503:physiopathology; D009426:Netherlands / Q000453:epidemiology; D009483:Neuropsychological Tests; D010300:Parkinson Disease / Q000175:diagnosis* / Q000453:epidemiology / Q000503:physiopathology; D011446:Prospective Studies; D011788:Quality of Life
chemical_list: D007980:Levodopa