title: Second-hand smoke, cotinine levels, and risk of circulatory mortality in a large cohort study of never-smokers.
abstract: BACKGROUND
  Exposure to second-hand smoke has been shown to be associated with increased cardiovascular mortality in several, but not all, epidemiologic studies. Our aim was to investigate the risk of circulatory death associated with exposure to second-hand smoke in never-smokers in a very large prospective study, the European Prospective Investigation into Cancer and Nutrition. A secondary aim was to use cotinine levels for cross-validating self-reported second-hand smoke exposure.
  
  
  METHODS
  Cox proportional hazard models were used to investigate the risk of death due to circulatory causes associated with second-hand smoke exposure in 135,233 never-smokers. Exposure to second-hand smoke was assessed through a questionnaire at enrollment and then validated against plasma cotinine measurements in a subsample.
  
  
  RESULTS
  Study participants who reported second-hand smoke exposure at home had higher cotinine levels (median plasma cotinine concentration in exposed = 0.82 microg/L; in those unexposed 0.02 microg/L). Second-hand smoke exposure at home was associated with an increased risk of dying from cardiovascular diseases (hazard ratio [HR] = 1.38 [95% confidence interval = 1.01-1.90]), all circulatory diseases (1.28 [0.98-1.69]), and coronary heart disease (1.31 [0.83-2.08]) after adjustment for age, sex, education, physical activity, and body mass index. Dose-response relationships were observed between exposure to second-hand smoke at home and risk of circulatory death (HR per each additional hour/d = 1.25 [1.04-1.50]). Having a partner who smokes more than 30 cigarettes per day considerably increased the risk of a circulatory death (2.94 [1.11-7.78]). Second-hand smoke exposure at home was not associated with total mortality (1.03 [0.93-1.13]).
  
  
  CONCLUSIONS
  Exposure to second-hand smoke at home (as confirmed by plasma cotinine levels) increases the risk of cardiovascular mortality.
authors.affiliation: Division of Epidemiology, Public Health and Primary Care, Imperial College, London W2 1PG, United Kingdom. v.gallo@imperial.ac.uk
authors.forename: Valentina
authors.initials: V
authors.lastname: Gallo
authors.forename: David
authors.initials: D
authors.lastname: Neasham
authors.forename: Luisa
authors.initials: L
authors.lastname: Airoldi
authors.forename: Pietro
authors.initials: P
authors.lastname: Ferrari
authors.forename: Mazda
authors.initials: M
authors.lastname: Jenab
authors.forename: Paolo
authors.initials: P
authors.lastname: Boffetta
authors.forename: Kim
authors.initials: K
authors.lastname: Overvad
authors.forename: Anne
authors.initials: A
authors.lastname: Tjønneland
authors.forename: Francoise
authors.initials: F
authors.lastname: Clavel-Chapelon
authors.forename: Heiner
authors.initials: H
authors.lastname: Boeing
authors.forename: Valeria
authors.initials: V
authors.lastname: Pala
authors.forename: Domenico
authors.initials: D
authors.lastname: Palli
authors.forename: Salvatore
authors.initials: S
authors.lastname: Panico
authors.forename: Rosario
authors.initials: R
authors.lastname: Tumino
authors.forename: Larraitz
authors.initials: L
authors.lastname: Arriola
authors.forename: Eiliv
authors.initials: E
authors.lastname: Lund
authors.forename: Bas
authors.initials: B
authors.lastname: Bueno-De-Mesquita
authors.forename: Petra H
authors.initials: PH
authors.lastname: Peeters
authors.forename: Olle
authors.initials: O
authors.lastname: Melander
authors.forename: Goran
authors.initials: G
authors.lastname: Hallmans
authors.forename: Elio
authors.initials: E
authors.lastname: Riboli
authors.forename: Rodolfo
authors.initials: R
authors.lastname: Saracci
authors.forename: Paolo
authors.initials: P
authors.lastname: Vineis
mesh_terms: D000367:Age Factors; D002318:Cardiovascular Diseases / Q000209:etiology / Q000401:mortality*; D015331:Cohort Studies; D016001:Confidence Intervals; D003327:Coronary Disease / Q000209:etiology / Q000401:mortality; D003367:Cotinine / Q000097:blood*; D004305:Dose-Response Relationship, Drug; D005060:Europe / Q000453:epidemiology; D005191:Family Characteristics; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D016016:Proportional Hazards Models; D012307:Risk Factors; D012737:Sex Factors; D014028:Tobacco Smoke Pollution / Q000009:adverse effects* / Q000706:statistics & numerical data
chemical_list: D014028:Tobacco Smoke Pollution; D003367:Cotinine