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ICD Code: 493. Asthma

ICD Code: 493. Article Review
Title: Sunyer J et al; "Risk Factors for Asthma in Young Adults." Eur Respir J; V.10; 1997; p2490
      STUDY DESIGN: This study forms part of the European Community Respiratory Health survey (ECRHS). A sample of 16,884 subjects aged 20-44 years was randomly selected from the general population of five areas in Spain. In a second phase, a random subsample of 3310 subjects from the original sample was selected. In addition, 1029 individuals who reported "symptoms related with asthma" but were not included in the random subsample, were also invited to participate in the second phase. From March 1992 to April 1993, subjects were invited to attend a center in each city. The ECRHS questionnaire on respiratory symptoms and environmental risk factors was completed, in addition to basic spirometry, a dose-response methacholine challenge test, and total and specific serum IgE responses to pets, pollen, and mold levels. Overall, 2646 individuals responded to the ECRHS respiratory questionnaire and 1797 individuals completed a bronchial responsiveness challenge.
      PEDIATRIC PREVALENCE RATES: The term "past asthma" is used here to describe asthma beginning in childhood but no longer active. For individuals aged 15 years or under, the prevalence is shown for current asthma versus past asthma, as follows: Female sex (1.3% vs 3.0%), parental asthma (6.9% vs 4.7%), indoor atopy (4.2% vs 7.1%), outdoor atopy (2.4% vs 4.0%), both indoor and outdoor atopy (9.3% vs 16.4%), having 1-2 older siblings (2.2% vs 1.3%), having 0 older siblings (1.9% vs 1.8%), lower respiratory infection (LRI) before the age of 5 years (11.1% vs 25.5%), exposure to any animal (1.9% vs 3.5%).
      ADULT PREVALENCE RATES: For individuals aged older than 15 years the prevalence is shown for current asthma versus past asthma, as follows: Female sex (5.1% vs 3.2%), parental asthma (6.4% vs 7.4%), indoor atopy (4.9% vs 3.7%), outdoor atopy (8.3% vs 6.2%), both indoor and outdoor atopy (17.2% vs 4.3%), having 1-2 older siblings (1.5% vs 1.1%), having 0 older siblings (1.8% vs 1.0%), LRI before the age of 5 years (6.2% vs 0.9%), exposure to any animal (3.2% vs 2.6%).
      ALLERGY AND ASTHMA: The strong association of asthma with atopy has been well described previously. The current study found a strong association with sensitization to seasonal allergens, with a magnitude similar to that for perennial allergens both in current and past asthma. In children, seasonal allergens are believed to be unrelated to asthma. In this study a significant association was found, though atopy was measured in adulthood. Outdoor allergens in adults have been related with epidemic and endemic presentations of emergency room admissions for asthma. This suggests that seasonal allergens might have an important role in asthma during adulthood, as was found in the analysis of the independent association of common aeroallergens with bronchial responsiveness. The association between asthma and atopy was stronger for current asthma than for past asthma. The authors could not exclude the possibility that the lack of temporal coincidence between measurement of atopy and occurrence of asthma symptoms explained this difference. An alternative explanation for the lower association of atopy with past asthma, and to a lesser extent with parental asthma and family size, is that there was a higher rate of misclassification for past asthma.
      OTHER RISK FACTORS: Lower respiratory tract infection (LRTI) in childhood was associated with a high risk of onset of asthma in childhood, while birth order was inversely associated. Respiratory infections, in particular those leading to bronchiolitis, might be a risk factor for asthma. An inverse association with birth order, explained by a higher frequency of secondary infections in larger families, has been reported previously with wheezing in children, coinciding with reports of an association between birth order or family size and hay fever. This contradictory pattern may be related to the timing (or the type) of infections in childhood.
      The authors found an inverse association with having had a pet during childhood. Having a pet has been considered a risk factor for asthma attacks, but also protective in rural children. The current finding could be due to a self-selection of symptomatic subjects who avoided having a pet.
      CONCLUSION: In addition to the known risk factors of asthma (atopy to perennial allergens, parental asthma), the authors have provided evidence for an association of asthma (whatever the age of onset) with sensitization to seasonal allergens and having less than three older siblings. There was also an association of childhood asthma with lower respiratory tract infection.

Search Criteria: Text - Eur Respir J; V.10; 1997; p2490