The relationship between the duration and severity of asthma

BACKGROUND: The relationship between the duration and severity of asthma has not been comprehensively investigated. METHODS: We examined the relationship between duration of asthma and asthma severity among 4776 patients with asthma: 608 with childhood-onset persistent asthma (12.7%), 187 with adolescent-onset asthma (3.9%), and 3981 with adult-onset asthma (83.4%). The assessment of asthma severity was based on the Japanese Guidelines for The Diagnosis and Treatment of Allergic Diseases, 2007 (JGL 2007). RESULTS: Asthma severity was assessed at 2 years, 3 to 10 years. 11 to 20 years, and 21 years or longer after disease onset. Disease severity significantly increased with greater asthma duration (p or = 300 IU/ml), smoking status, house dust mite-specific serum IgE antibody level, or gender. CONCLUSION: Our findings suggest that bronchial asthma is a disease that worsens over time.