title: Investigation into the increase in hay fever and eczema at age 16 observed between the 1958 and 1970 British birth cohorts.
abstract: OBJECTIVE
  To investigate whether changes in certain perinatal and social factors explain the increased prevalence of hay fever and eczema among British adolescents between 1974 and 1986.
  
  
  METHODS
  Two prospective birth cohort studies.
  
  
  METHODS
  England, Wales, and Scotland.
  
  
  METHODS
  11,195 children born 3-9 March 1958 and 9387 born 5-11 April 1970.
  
  
  METHODS
  Parental reports of eczematous rashes and of hay fever or allergic rhinitis in the previous 12 months at age 16.
  
  
  RESULTS
  The prevalence of the conditions over the 12 month period increased between 1974 and 1986 from 3.1% to 6.4% (prevalence ratio 2.04 (95% confidence interval 1.79 to 2.32)) for eczema and from 12.0% to 23.3% (prevalence ratio 1.93 (1.82 to 2.06)) for hay fever. Both conditions were more commonly reported among children of higher birth order and those who were breast fed for longer than 1 month. Eczema was more commonly reported among girls and hay fever among boys. The prevalence of hay fever decreased sharply between social classes I and V, increased with maternal age up to the early 30s, and was lower in children whose mothers smoked during pregnancy. Neither condition varied significantly with birth weight. When adjusted for these factors, the relative odds of hay fever (1986 v 1974) increased from 2.23 (2.05 to 2.43) to 2.40 (2.19 to 2.63). Similarly, the relative odds of eczema rose from 2.02 (1.73 to 2.36) to 2.14 (1.81 to 2.52).
  
  
  CONCLUSIONS
  Taken together, changes between cohorts in sex, birth weight, birth order, maternal age, breast feeding, maternal smoking during pregnancy, and father's social class at birth did not seem to explain any of the observed rise in the prevalence of hay fever and eczema. However, correlates of these factors which have changed over time may still underlie recent increases in allergic disease.
authors.affiliation: Department of Public Health Sciences, St George's Hospital Medical School, London.
authors.forename: B K
authors.initials: BK
authors.lastname: Butland
authors.forename: D P
authors.initials: DP
authors.lastname: Strachan
authors.forename: S
authors.initials: S
authors.lastname: Lewis
authors.forename: J
authors.initials: J
authors.lastname: Bynner
authors.forename: N
authors.initials: N
authors.lastname: Butler
authors.forename: J
authors.initials: J
authors.lastname: Britton
mesh_terms: D000293:Adolescent; D001722:Birth Order; D001942:Breast Feeding; D015331:Cohort Studies; D004485:Eczema / Q000453:epidemiology*; D005260:Female; D006801:Humans; D008297:Male; D008423:Maternal Age; D011247:Pregnancy; D015995:Prevalence; D011446:Prospective Studies; D006255:Rhinitis, Allergic, Seasonal / Q000453:epidemiology*; D012307:Risk Factors; D012923:Social Class; D012959:Socioeconomic Factors; D006113:United Kingdom / Q000453:epidemiology