Risk factors of childhood asthma in Sao Jose do Rio Preto, Sao Paulo, Brazil

Epidemiological studies have shown increased prevalence of asthma over the last decades and a considerable variation in these rates between different countries, mainly developed. Changes in lifestyle of different populations could explain the increasing prevalence of asthma and its different rates in different communities.

A case-control study was conducted to investigate some risks factors associated to asthma in schoolchildren in São José do Rio Preto, São Paulo, Brazil.

A total of 3793 self-administered written questionnaire (WQ) was filled in by parents of 6-7-year-old schoolchildren, applying the International Study of Asthma and Allergies in Childhood (ISAAC) protocol. Additionally, was added a supplementary WQ evaluating risk factors: gender, personal history of rhinitis and atopic eczema, familial history of atopy, older siblings, day care, breastfeeding, and exposure to pets and to cigarette smoking. Children whose parents responded affirmatively to question 'Has your child had wheezing in the past 12 monthsquest;' were identified as having current asthma.

The prevalence of current asthma was 18.3%. In multivariate analysis the following risk factors were associated with asthma: rhinitis (OR = 10.6; 95% CI = 8.27-13.56), atopic eczema (OR = 1.54; 95% CI = 1.00-2.35), father with asthma (OR = 3.49; 95% CI = 1.83-6.67), mother with asthma (OR = 1.84; 95% CI = 1.11-3.05), current exposure to pets (OR = 1.83; 95% CI = 1.45-2.32) and passive tobacco smoking exposure (OR = 1.43; 95% CI = 1.12-1.83).

Our results show that genetic background, environmental factors and the presence of co-morbidities such as rhinitis and atopic eczema are associated to the genesis of asthma in Brazilian schoolchildren.