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ICD Code: 493. Asthma



ICD Code: 493. Article Review
Title: Pearce N et al; "Worldwide Trends in the Prevalence of Asthma Symptoms: Phase III of the International Study of Asthma and Allergies in Childhood (ISAAC)." Thorax; V.62; 2007; p757
      STUDY DESIGN: In phase I of the International Study of Asthma and Allergies in Childhood (ISAAC), children aged 13-14 years were studied in 155 centers in 56 countries and children aged 6-7 years were studied in 91 centers in 38 countries. Up to 20-fold variations in the prevalence of “current wheeze” (in the last 12 months) were observed between centers worldwide (range 1.8% to 36.7%), with a 7-fold variation observed between the 10th and 90th percentiles (4.4%, 30.9%).
      Phase III has involved repeating the phase I survey after 5-10 years to examine time trends in the prevalence of asthma, allergic rhinoconjunctivitis and eczema in centers and countries that participated in phase I. Phase III was conducted following as precisely as possible the methods used in phase I. It included two groups of centers: (1) Group A are centers that previously completed phase I according to the ISAAC phase I protocol, including centers for which the phase I data were submitted too late for inclusion in the first worldwide publications but were of the required standard; (2) Group B are centers from around the world that did not participate in phase I but participated in phase III as new centers.
      GLOBAL PREVALENCE TRENDS: The findings reported here are of considerable interest. First, they show that in most high prevalence countries, particularly the English language countries, the rise in the prevalence of asthma symptoms has peaked and may even have begun to decline. This is consistent with the findings of other recent studies in children and in adults. There are some exceptions to this trend, but of the European and English language countries which showed a relatively high prevalence in phase I, only Germany and Finland have shown significant increases in symptom prevalence in phase III. The increases for North America are due to increases in Barbados (where the phase I data were too late for inclusion in the phase I paper); the one U.S. center showed a small decline in symptom prevalence consistent with the findings for other English language countries.
      Second, a number of countries that had high or intermediate levels of symptom prevalence in phase I have shown significant increases in prevalence in phase III; these include Latin American countries such as Costa Rica, Panama, Mexico, Argentina and Chile, and Eastern European countries such as the Ukraine and Romania. Other countries to show significant increases in symptom prevalence included Barbados, Tunisia, Morocco and Algeria. Third, with the exception of India, all of the countries with very low symptom prevalence rates in phase I reported increases in prevalence in phase III, although only the increases for Indonesia and China were statistically significant.
      Finally, virtually all countries, irrespective of the level of symptom prevalence, reported increases in lifetime asthma prevalence between phases I and III. In fact, the increases were most marked in those countries with the highest mean prevalence between phase I and phase III, despite the fact that many of these countries reported declines in the prevalence of asthma symptoms between phase I and phase III.
      DISCUSSION: Perhaps the most striking finding is the apparent decline in symptom prevalence in English language countries. Just as we do not (yet) know why prevalence has increased since the 1950s, we do not know why it should now be decreasing.

Search Criteria: Text - Thorax; V.62; 2007; p757