title: Self-reported headache frequency in Canadian adolescents: validation and follow-up.
abstract: OBJECTIVE
  To validate our previous estimates of the prevalence of frequent headache and associated factors in a new sample of 12- to 13-year-old adolescent Canadians, and to explore if estimates of the prevalence of frequent headache and associated factors remain stable within the original cohort after a two-year interval.
  
  
  METHODS
  We analyzed the self-administered questionnaire microdata files of the National Longitudinal Survey of Children and Youth (NLSCY: 1998-1999). 1694 respondents representing 724,400 youth aged 12 to 13 years were used to validate the prevalence in our initial estimates. From the initial cohort, 1764 respondents representing 819,600 youth, now aged 14 to 15 years, were used to examine whether frequent headache prevalence or associated factors had changed in the intervening two years.
  
  
  RESULTS
  Among the analyzed individuals, 26.3% of 12- to 13-year olds and 31.2% of 14- to 15-year olds reported frequent headaches of "about once a week" or more often (P= .001). Our previous study of the NLSCY: 1996-1997 found a prevalence of 26.6% in 12- to 13-year olds. We previously identified 22 risk factors, of which 15 were replicated and one proxy was available within this iteration of the survey. For the 12- to 13-year olds, 14/16 were associated (P < .01, chi-square) with frequent headaches. For the initial cohort, now 14- to 15-year olds, 15/16 risk factors remained associated (P < .01, chi-square) with an increased risk of headaches.
  
  
  CONCLUSIONS
  Our estimates of frequent headache prevalence are reliable and consistent in two large nationally representative cohorts of 12- to 13-year olds. In the first of these groups there was an increase in prevalence over 2 years as adolescence progresses. Our identified risk factors for frequent headaches have been validated within another cohort and are maintained as the cohort ages.
authors.affiliation: Dalhousie University, IWK Health Centre, Department of Pediatrics, Halifax, NS, Canada.
authors.forename: Joseph M
authors.initials: JM
authors.lastname: Dooley
authors.forename: K E
authors.initials: KE
authors.lastname: Gordon
authors.forename: E P
authors.initials: EP
authors.lastname: Wood
mesh_terms: D000293:Adolescent; D002170:Canada / Q000453:epidemiology; D002648:Child; D015331:Cohort Studies; D005500:Follow-Up Studies; D006261:Headache / Q000453:epidemiology* / Q000209:etiology; D006801:Humans; D015995:Prevalence; D015203:Reproducibility of Results; D012307:Risk Factors; D011795:Surveys and Questionnaires / Q000592:standards