title: A systematic review of the worldwide prevalence and incidence of Parkinson's disease.
abstract: BACKGROUND
  A number of epidemiologic studies of Parkinson 's disease (PD) have been conducted worldwide over the years. Although every study reported the rise in prevalence and incidence rate of PD with the increasing age, the overall estimates were different across countries. The variation in reported data may partly be contributed by case ascertainment, case finding method, data collection, and most importantly different population structures.
  
  
  OBJECTIVE
  Systematically review prevalence and incidence of PD and find the causes of variation in the results.
  
  
  METHODS
  A literature search was conducted on Medline and EMBASE for studies worldwide investigating the prevalence and incidence of PD and included all adults, English and publication between 1965 and January 2010. The primary search of both databases yielded 5,330 results. After screening topics and abstracts, 168 relevant abstracts were tagged and saved for more thorough perusal. Ultimately, 40 papers were selected for review after applying the pre-specified inclusion criteria
  
  
  RESULTS
  The worldwide prevalence of PD varies widely. One reason for the variation in prevalence estimates could be due to the differences in survival across countries. The use of epidemiological studies using medical records could be another reason for the variation in disease frequency.
  
  
  CONCLUSIONS
  PD is common in the elderly. A number of descriptive epidemiologic studies have been conducted worldwide. Comparing the incidence and prevalence of Parkinson's disease is difficult.
authors.affiliation: Department of Preventive and Social Medicine, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand. drweerasak@gmail.com
authors.forename: Weerasak
authors.initials: W
authors.lastname: Muangpaisan
authors.forename: Aju
authors.initials: A
authors.lastname: Mathews
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Hori
authors.forename: David
authors.initials: D
authors.lastname: Seidel
mesh_terms: D017677:Age Distribution; D000368:Aged; D000369:Aged, 80 and over; D001208:Asia / Q000453:epidemiology; D003625:Data Collection; D016021:Epidemiologic Studies; D005060:Europe / Q000453:epidemiology; D005260:Female; D006801:Humans; D015994:Incidence; D008297:Male; D010300:Parkinson Disease / Q000145:classification / Q000453:epidemiology* / Q000209:etiology; D015995:Prevalence; D012307:Risk Factors; D017678:Sex Distribution