title: Risk of Parkinson's disease among first-degree relatives: A community-based study.
abstract: OBJECTIVE
  To determine the relative risk (RR) and cumulative incidence of idiopathic Parkinson's disease (PD) in first-degree relatives of PD patients compared with relatives of controls from the same geographic region.
  
  
  METHODS
  A family history questionnaire was used to obtain information on all first-degree relatives of cases and controls. A subset of these first-degree relative was also examined. A Cox proportional hazards model with double-censoring techniques for missing information was used to model the RR for PD, adjusting for gender, ethnicity, and relationship to proband.
  
  
  RESULTS
  A total of 1,458 first-degree relatives of 233 PD patients were 2.3 times as likely (95% CI = 1.3 to 4.0) as 7,834 relatives of 1,172 controls to develop PD. The cumulative incidence of PD to age 75 among first-degree relatives of PD patients was 2% compared with 1% among first-degree relatives of controls. The risk in male first-degree relatives was higher than in female relatives (RR = 2.0, 95% CI = 1.1 to 3.4) and the risk in relatives of Caucasians was higher than in African-Americans and Hispanics (RR = 2.4, 95% CI = 1.4 to 4.1). Risk for siblings and parents of probands was similar.
  
  
  CONCLUSIONS
  Susceptibility to PD is increased in first-degree relatives of both sporadic and familial cases. The pattern of inheritance and the relationship between genetic and environmental risk factors warrant further study.
authors.affiliation: Gertrude H. Sergievsky Center, College of Physicians and Surgeons, New York, New York, USA.
authors.forename: K
authors.initials: K
authors.lastname: Marder
authors.forename: M X
authors.initials: MX
authors.lastname: Tang
authors.forename: H
authors.initials: H
authors.lastname: Mejia
authors.forename: B
authors.initials: B
authors.lastname: Alfaro
authors.forename: L
authors.initials: L
authors.lastname: Côté
authors.forename: E
authors.initials: E
authors.lastname: Louis
authors.forename: J
authors.initials: J
authors.lastname: Groves
authors.forename: R
authors.initials: R
authors.lastname: Mayeux
mesh_terms: D000368:Aged; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010300:Parkinson Disease / Q000235:genetics*; D012307:Risk Factors; D011795:Surveys and Questionnaires