Determinant of persistent asthma and new asthma onset in a longitudinal study with special reference to atopic sensitization

Our knowledge about atopy as a longitudinal predictor of asthma is limited. The purpose of this study was to investigate the prognosis of asthma and risk factors for asthma onset, especially sensitization of specific allergens in a population sample. A cohort responded to a respiratory questionnaire in 1990 and 2003. At baseline, 1851 subjects who, in the screening questionnaire, reported respiratory symptoms and 447 controls were investigated with interviews, spirometry and skin prick test. A total of 721 asthmatics and 976 subjects without respiratory disease were clinically verified. At follow-up in 2003, 340 subjects with persistent asthma and 186 subjects with asthma remission were identified while 76 subjects reported new asthma onset. Sensitisation to pets and a high symptom score were significant determinants of persistent asthma (Odds Ratio [ORs] 3.2 [95% CI 1.9-5.6], and 5.7 [2.5-13.3] respectively), and onset of asthma, (ORs 2.6 [1.1-6.0], and 1.7 [1.2-2.3], respectively). A high self-reported responsiveness to airway irritants (OR 1.6 [1.1-2.2]), and more asthma medications (OR 2.0 [1.3-2.9]) were additional risk factors for persistent asthma at the follow-up. Belonging to the older age group decreased the risk both of having persistent asthma and asthma onset. In conclusion, asthmatics sensitised to pets have a more severe outcome than asthmatics not sensitised to pets. Sensitisation to pets was also a strong predictor for onset of asthma. Our study also indicates that special attention should be given to asthmatics that report having severe symptoms and problems with airway irritants as such patients are more likely to have persistent problems.