Age of onset and the characteristics of asthma

The aim of this study was to evaluate the characteristics of asthma in patients with different ages of disease onset.

Five hundred and four asthmatic patients (303 males and 201 females) were divided into five groups based on age of onset (group I, age of onset < 15 years old; group II, 15-24 years old; group III, 25-44 years old; group IV, 45-64 years old; and group V, > 64 years old). The relationship between age of onset and the characteristics of asthma, including lung function, reversibility, atopic status and the incidence of coexistent allergic rhinitis was assessed. Multivariate analysis, adjusted for the duration of disease, gender, educational level, smoking status, and degree of previous inhaled corticosteroid treatment, was performed.

Thirty per cent of the patients developed asthma before they were 14 years old (group I), and the percentages of those developing asthma at other ages of onset were: group II, 12%; group III, 29%; group IV, 21% and group V, 8%. In all, 57.6% of the asthmatic patients had coexistent allergic rhinitis; younger patients tended to have this comorbidity. The pulmonary function of older onset asthma patients was worse than that of early onset patients. The multivariate analysis showed that there was a positive correlation between the reduction of pulmonary function and duration of the disease (P < 0.001), but there was no relationship between pulmonary function and gender (P = 0.502), educational level (P = 0.734), smoking pack-years (P = 0.902), or degree of use of inhaled corticosteroid treatment (P = 0.586).

Asthma is a heterogeneous disease with a wide variety of presentations. This study provides information about the disease characteristics and their relationship with age of onset. Further study is necessary to determine why these differences exist.