title: Active and passive smoking and risk of narcolepsy in people with HLA DQB1*0602: a population-based case-control study.
abstract: BACKGROUND
  We examined the risk of narcolepsy associated with active and passive smoking among genetically susceptible individuals.
  
  
  METHODS
  We conducted a population-based case-control study in King County, Wash., USA. Between 2001 and 2005, we enrolled 67 cases through physicians and public outreach, and 95 controls through random-digit dialing. Subjects were aged between 18 and 50 years and positive for HLA DQB1*0602. All subjects were administered in-person interviews about their history of active and passive smoking.
  
  
  RESULTS
  We observed an increased risk of narcolepsy associated with having lived with two or more household smokers (odds ratio, OR = 5.1; 95% confidence interval, CI: 1.6, 12.1); with a grandparent or a sibling who smoked (OR = 3.0; 95% CI: 1.1, 8.3); with a non-family household member who smoked (OR = 3.7; 95% CI: 1.6, 8.6); and with an unrelated smoker for 1-2 years (OR = 3.1; 95% CI: 1.0, 9.0). The risk of narcolepsy was not associated with exposure to smoke at work or with active smoking before age 21 or before age of narcolepsy onset.
  
  
  CONCLUSIONS
  Passive smoking may be a risk factor for narcolepsy in subjects with HLA DQB1*0602. Future studies could help clarify whether passive smoking is an important etiologic component of narcolepsy among genetically susceptible individuals.
authors.affiliation: Neuroepidemiology Group, School of Public Health and Community Medicine, University of Washington, Seattle, WA, USA. thanhton@u.washington.edu
authors.forename: Thanh G N
authors.initials: TG
authors.lastname: Ton
authors.forename: W T
authors.initials: WT
authors.lastname: Longstreth
authors.forename: Thomas
authors.initials: T
authors.lastname: Koepsell
mesh_terms: D000293:Adolescent; D000328:Adult; D016022:Case-Control Studies; D005260:Female; D020022:Genetic Predisposition to Disease; D006683:HLA-DQ Antigens / Q000235:genetics*; D059866:HLA-DQ beta-Chains; D006801:Humans; D008297:Male; D008562:Membrane Glycoproteins / Q000235:genetics*; D008875:Middle Aged; D009290:Narcolepsy / Q000453:epidemiology / Q000209:etiology* / Q000235:genetics*; D011153:Population; D012307:Risk Factors; D012907:Smoking / Q000009:adverse effects* / Q000453:epidemiology / Q000235:genetics*; D014028:Tobacco Smoke Pollution / Q000009:adverse effects* / Q000706:statistics & numerical data; D055815:Young Adult
chemical_list: D006683:HLA-DQ Antigens; D059866:HLA-DQ beta-Chains; C069051:HLA-DQB1 antigen; D008562:Membrane Glycoproteins; D014028:Tobacco Smoke Pollution