Asthma in adolescents--Prevalence trends and associated factors in northeast Brazil

Asthma is the most common chronic disease affecting children and adolescents (AD). We evaluated the prevalence of asthma and associated factors in adolescents living in a developing region in northeast Brazil using the ISAAC (International Study of Asthma and Allergies in Childhood) methodology.

According to the ISAAC protocol, AD (13-14 year olds, n=3,043 in 2003 and 3,009 in 2011-12) answered the standardised written questionnaire by themselves. In addition, in 2011-12 a random sample of these AD (n=430) also answered a complementary questionnaire (associated factors) and underwent a skin prick test with aeroallergens (Dermatophagoides pteronyssinus, Blomia tropicalis, Blatella germanica, Periplaneta americana, dog dander, cat dander, mixed grass pollen and mixed moulds, including 10mg/mL histamine and negative controls). Data were analysed by univariate and multivariate analysis using Poisson regression.

The prevalence of asthma in 2011-12 in Aracaju was 12.8%, which is lower than that recorded in 2003 (18.7%). Individuals with a dog outside the home (PR=0.93; 95%CI=0.88-0.98; p=0.018) and those with an older sibling (PR=0.94; 95%CI=0.91-0.98; p=0.005) were identified as protective. The presence of smokers in the residence (PR=1.04; 95%CI=1.00-1.09; p=0.039) was associated with an increased risk of developing asthma.

The prevalence of asthma was significantly lower than the last ISAAC figures reported for Aracaju. Tobacco smoking, a preventable factor, continues to be associated with an increase in the occurrence of asthma and other associations may concur with the hygiene hypothesis.