title: Is it exposure to cigarette smoke or to smokers which increases the risk of meningococcal disease in teenagers?
abstract: BACKGROUND
  Passive smoking appears to increase the risk of meningococcal disease (MD) in adolescents. Whether this effect is attributable to exposure to cigarette smoke or contact with smokers is unknown.
  
  
  METHODS
  We conducted a prospective population-based case-control study with age, sex matched-controls in 1:1 matching. Participants were 15-19 year old with MD recruited at hospital admission in six regions (65% of the population of England) from January 1999 through June 2000, and their matched controls. Data on potential risk factors were gathered by confidential interview, including seven passive smoking variables. Factor analysis was performed to assess the dimensionality of the passive smoking exposure variables. The data were analysed with univariate and multivariate conditional logistic regression.
  
  
  RESULTS
  144 case-control pairs were recruited (51% male; median age 17.6). Factor analysis identified two independent factors representing passive smoking (P < 0.01), one associated with 'exposure to smoke', the other with 'smoker contact'. Only smoker contact was a significant risk factor for MD (OR = 1.8; 95% CI 1.0-3.3; P = 0.05). In multivariate analysis this factor was still associated with MD independently of potential confounders such as active smoker status and household crowding.
  
  
  CONCLUSIONS
  Contact with smokers is associated with increased risk of MD in adolescents. This is more likely to be due to higher carriage rates in smokers than to exposure to smoke and emphasizes the importance of public health measures to stop smoking. In epidemiological studies that assess risk from passive smoking, exposure to smoke should be differentiated where possible from contact with smokers.
authors.affiliation: Academic Department of Child Health, Queen Mary, University of London, Royal London Hospital, UK. pietro.coen@uclh.nhs.uk
authors.forename: Pietro G
authors.initials: PG
authors.lastname: Coen
authors.forename: Joanna
authors.initials: J
authors.lastname: Tully
authors.forename: James M
authors.initials: JM
authors.lastname: Stuart
authors.forename: Deborah
authors.initials: D
authors.lastname: Ashby
authors.forename: Russell M
authors.initials: RM
authors.lastname: Viner
authors.forename: Robert
authors.initials: R
authors.lastname: Booy
mesh_terms: D000293:Adolescent; D000328:Adult; D004739:England / Q000453:epidemiology; D004781:Environmental Exposure / Q000009:adverse effects / Q000032:analysis; D004812:Epidemiologic Methods; D005260:Female; D006801:Humans; D008297:Male; D008589:Meningococcal Infections / Q000453:epidemiology / Q000209:etiology* / Q000635:transmission; D012907:Smoking; D014028:Tobacco Smoke Pollution / Q000009:adverse effects* / Q000706:statistics & numerical data
chemical_list: D014028:Tobacco Smoke Pollution