Factors associated with severe asthma.

OBJECTIVE:To study the role of various factors associated with development and severity of bronchial asthma in children between 5-15 years of age. SETTING: Tertiary Care Medical College Hospital. METHODS: A case control study was carried out during May 96 to April 98. Sixty children each suffering from mild (chronic) and severe asthma (chronic) and 60 controls were enrolled to study the association of various risk factors with development of asthma and for severe disease. RESULTS: On univariate analysis factors associated with significant risk for development of asthma included family history of asthma (p = 0.003), lack of exclusive breastfeeding (p = 0.05), past history of bronchiolitis (p = 0.02), associated allergic rhinitis (p = 0.04) and atopic dermatitis (p = 0.01). For development of severe asthma, associated factors were early onset of symptoms (p = 0.01), family history of asthma in grandparents (p = 0.04) and more than 10 cigarettes per day smoked by any family member. No significant effect of air pollution, overcrowding, pets and passive smoking were found on either development of asthma or it's severity. On multivariate analysis only age of onset below 48 months was associated with severe asthma (OR 2.13, 95% CI 1.00-4.54). Exclusive breastfeeding for more than 4 months was the most protective factor for development of asthma (OR 0.25, 95% CI 0.08-0.70). A strong association between development of asthma and past history of bronchiolitis or tuberculosis (OR 5.26, 95% CI 1.7-16.20) and presence of associated atopic dermatitis or rhinitis (OR 7.5, 95% CI 1.64-34.48) was observed. CONCLUSION: History of associated allergic diseases and past history of bronchiolitis were significantly associated with development of asthma. Exclusive breastfeeding for first 4 months of life was protective. The most significant factor associated with severe asthma was onset of illness before 48 months of age. There was no significant effect of air pollution, over crowding, pets at home or passive smoking on severity of asthma