title: Asthma epidemiology: has the crisis passed?
abstract: OBJECTIVE
  Asthma is a difficult, resource-intensive disease that can result in symptoms, hospitalization and, in rare cases, death. In the past few decades, there has been an abundance of evidence showing the prevalence of asthma to be increasing in certain regions. However, reports have recently emerged suggesting that asthma prevalence has stabilized. This has led to debate among researchers whether increases in asthma prevalence have come to an end. We reviewed recent literature in search of answers to the ongoing debate on whether the asthma crisis is over.
  
  
  RESULTS
  In contrast with past reports, several recent studies have reported a stabilization of asthma prevalence. However, based on repeated cross-sectional studies, findings regarding the stabilization of asthma prevalence have been inconsistent, especially when considering the heterogeneity of the disease, which can result in a variety of patterns concerning asthma diagnosis, symptoms, and allergic sensitization. Temporal trends considering physician visits, hospitalizations, and mortality have been more consistent, with stabilizing and decreasing patterns of asthma burden in recent years.
  
  
  CONCLUSIONS
  Because reasons for the original increases in asthma prevalence remain unclear, an explanation for the apparent stabilization of asthma prevalence reported in some studies also remains elusive. This is compounded by the difficulty in defining asthma accurately in population studies and inconsistencies in the results of prevalence estimation among repeated cross-sectional studies. Efforts should be made to continue monitoring asthma prevalence and to begin monitoring asthma prevalence in regions where environmental and social changes are occurring.
authors.affiliation: Department of Public Health Sciences, University of Alberta, Edmonton, Alberta, Canada.
authors.forename: Joshua Allan
authors.initials: JA
authors.lastname: Lawson
authors.forename: Ambikaipakan
authors.initials: A
authors.lastname: Senthilselvan
mesh_terms: D001249:Asthma / Q000453:epidemiology*; D006760:Hospitalization / Q000639:trends; D006801:Humans; D009017:Morbidity / Q000639:trends