Time interval and the factors associated with the development of asthma in patients with allergic rhinitis.

Rhinitis and asthma commonly coexist and studies have shown a positive association between rhinitis and asthma in both atopic and nonatopic adults. Longitudinal studies have shown that in many cases rhinitis precedes the onset of asthma. The aims of this study were to study the time interval for the development of asthma after the onset of rhinitis, to determine the proportion of patients in whom rhinitis precedes asthma, and to study the factors associated with the development of asthma in patients with allergic rhinitis compared to patients who continue to have allergic rhinitis alone. This was a cross-sectional study done at a tertiary care allergy center in Mysore, South India. It included consecutive patients between 2004 and 2006 with allergic rhinitis and/or asthma. We used a structured questionnaire, clinical evaluation, spirometry, and skin-prick testing. A total of 1,141 subjects were included in the study. Among them, 700 had allergic rhinitis for varying intervals before developing asthma and 355 had rhinitis without asthma. In subjects aged 20 years or younger, logistic regression analysis confirmed an independent association with a family history of allergic rhinitis and sensitization to house dust mites as risk factors and ever-used nasal steroids as protective against developing asthma in subjects with allergic rhinitis. In subjects older than 20 years, a family history of allergic rhinitis, atopy, and sensitization to house dust mites and trees were risk factors and ever-user of nasal steroids was protective. Rhinitis often preceded asthma and a high proportion of patients, both children and adults, developed asthma within 2 years after the onset of rhinitis. A family history of allergic rhinitis, atopy, and sensitization to house dust mites and trees are associated with the development of asthma in patients with allergic rhinitis.