title: The frequency and validity of self-reported diagnosis of Parkinson's Disease in the UK elderly: MRC CFAS cohort.
abstract: BACKGROUND
  Estimates of the incidence and prevalence of chronic diseases can be made using established cohort studies but these estimates may have lower reliability if based purely on self-reported diagnosis.
  
  
  METHODS
  The MRC Cognitive Function & Ageing Study (MRC CFAS) has collected longitudinal data from a population-based random sample of 13004 individuals over the age of 65 years from 5 centres within the UK. Participants were asked at baseline and after a two-year follow-up whether they had received a diagnosis of Parkinson's disease. Our aim was to make estimates of the incidence and prevalence of PD using self-reporting, and then investigate the validity of self-reported diagnosis using other data sources where available, namely death certification and neuropathological examination.
  
  
  RESULTS
  The self-reported prevalence of Parkinson's disease (PD) amongst these individuals increases with age from 0.7% (95%CI 0.5-0.9) for 65-75, 1.4% (95%CI 1.0-1.7) for 75-85, and 1.6% (95%CI 1.0-2.3) for 85+ age groups respectively. The overall incidence of self reported PD in this cohort was 200/100,000 per year (95%CI 144-278). Only 40% of the deceased individuals reporting prevalent PD and 35% of those reporting incident PD had diagnoses of PD recorded on their death certificates. Neuropathological examination of individuals reporting PD also showed typical PD changes in only 40%, with the remainder showing basal ganglia pathologies causing parkinsonism rather than true PD pathology.
  
  
  CONCLUSIONS
  Self-reporting of PD status may be used as a screening tool to identify patients for epidemiological study, but inevitably identifies a heterogeneous group of movement disorders patients. Within this group, age, male sex, a family history of PD and reduced cigarette smoking appear to act as independent risk factors for self-reported PD.
authors.affiliation: Cambridge Centre for Brain Repair, University of Cambridge, Forvie Site, Robinson Way, Cambridge, CB2 2PY, UK. tf210@medschl.cam.ac.uk
authors.forename: Thomas
authors.initials: T
authors.lastname: Foltynie
authors.forename: Fiona E
authors.initials: FE
authors.lastname: Matthews
authors.forename: Lianna
authors.initials: L
authors.lastname: Ishihara
authors.forename: Carol
authors.initials: C
authors.lastname: Brayne
mesh_terms: D017677:Age Distribution; D000368:Aged; D000369:Aged, 80 and over; D015331:Cohort Studies; D005260:Female; D006801:Humans; D015994:Incidence; D008297:Male; D010300:Parkinson Disease / Q000175:diagnosis* / Q000453:epidemiology* / Q000523:psychology; D015995:Prevalence; D015203:Reproducibility of Results; D012650:Self Disclosure; D006113:United Kingdom