Trends in the age of diagnosis of childhood asthma

J Allergy Clin Immunol. 2014 Nov;134(5):1057-62.e5. doi: 10.1016/j.jaci.2014.05.012. Epub 2014 Jun 27.

Abstract

Background: The cause of rising asthma incidence over time remains unexplained. Examining trends in the age of diagnosis across successive birth cohorts may offer insights into asthma etiology.

Objective: To examine trends in the age at asthma diagnosis and the age and proportion of children hospitalized at first asthma diagnosis in Ontario, Canada.

Methods: Eight consecutive birth cohorts of children (1993-2000) were observed using administrative data from a universal health insurance plan in Ontario, Canada (population 13 million). Trends in the need for hospitalization and age at asthma diagnosis were examined with descriptive and survival analyses.

Results: The records of 1,059,511 children were examined, of whom 201,958 developed asthma in the first 8 years of life, with an average cumulative incidence of 19.1%. Mean age at asthma diagnosis decreased from 4.7 ± 1.5 years in birth year 1993 to 2.6 ± 2.0 years in birth year 2000 (P < .0001), with a higher adjusted risk of asthma diagnosis (hazard ratio, 6.7; 95% CI, 6.5-6.9) in the first 3 years of life for children born after 1996 versus children born in the period 1993 to 1995 (hazard ratio, 1.4; 95% CI, 1.3-1.4). The proportion of children hospitalized at asthma diagnosis stayed stable while the age at first asthma hospitalization decreased over time (P < .0001).

Conclusions: This study demonstrates a significant increase in asthma incidence and a decrease in the age of asthma diagnosis across multiple birth cohorts. Changes in asthma incidence over time are primarily explained by variations in asthma rates in children younger than 3 years.

Keywords: Asthma; administrative data; child; epidemiology; incidence; prevalence; rate.

Publication types

  • Clinical Trial
  • Multicenter Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Age of Onset
  • Asthma / diagnosis*
  • Asthma / epidemiology*
  • Asthma / therapy
  • Child
  • Child, Preschool
  • Female
  • Hospitalization
  • Humans
  • Incidence
  • Infant
  • Infant, Newborn
  • Male
  • Ontario / epidemiology
  • Retrospective Studies