Asthma and Allergic Diseases in School Children from 1992 to 2007 with Incidence Data

BACKGROUND: Information about change in the prevalence of asthma and allergic diseases and factors related with these diseases would be beneficial in decreasing the burden of these diseases. OBJECTIVE: To assess (i) change in prevalence of asthma and allergic diseases; (ii) factors associated with asthma and wheeze; and (iii) incidence of asthma and wheeze. METHODS: A questionnaire was administered to children aged 7-12 years in first five grades in the same primary school in 1992 (n: 1036), 1997 (n: 738), 2002 (n: 621), and 2007 (n: 422) and filled by the parents. A second survey in 2007 (n: 474, in eight grades) was conducted in the same schoolchildren, 6 months apart, to assess the incidence of asthma and wheeze and the associated factors. RESULTS: Comparison of 1992, 1997, 2002, and 2007 surveys revealed that prevalence of asthma (8.3%, 9.8%, 6.4%, 3.3%, respectively), wheeze (11.9%, 13.3%, 6.4%, 3.1%, respectively), hay fever (15.4%, 14.1%, 7.2%, 3.1%, respectively), and eczema (4.0%, 4.3%, 1.8%, 1.2%, respectively) were significantly lower in 2002 and 2007 compared with that in 1992. Percentage of passive smoking decreased after 1992 (74.0%, 64.0%, 64.1%, and 65.5%, respectively). Incidence of asthma and wheeze in 2007 surveys were 0.9/100 and 1.1/100, respectively. After the adjustment for age and gender, infection in the past, family atopy, and presence of atopic disease (eczema or hay fever) were associated with asthma and wheeze. Maternal smoking and lack of breast feeding were associated with asthma. Male gender, pet ownership in the past, lack of health insurance coverage, snoring, and wood or coal used as fuel were associated with wheeze. CONCLUSIONS: Decreased prevalence of asthma and allergic diseases in the last 10 years could be related to decreased rate of passive smoking. Lower socioeconomic status and lack of breast feeding could increase the risk of asthma in children.