Impact of Inhaled Corticosteroid Treatment on 15-Year Longitudinal Respiratory Function Changes in Adult Patients with Bronchial Asthma

Abstract

Background: Bronchial asthma is mainly controlled by inhaled corticosteroid (ICS) treatment, and discontinuation of ICS treatment can worsen asthma symptoms and reduce respiratory function. However, the longitudinal impact of ICS on lung function in adult patients is unknown. Methods: To determine whether regular ICS treatment can prevent long-term lung function deterioration in adults with bronchial asthma, we recruited 167 adult asthma patients who first visited Fukuoka National Hospital in 1995 and underwent lung function tests in 1995, 1996 and 2010. Regular ICS treatment was continued in 102 patients (regular group), while 39 patients received irregular ICS treatment (irregular group). Changes in lung function were compared retrospectively between the groups. The influences of smoking, disease severity and disease duration were also analyzed. Results: The forced expiratory volume in 1 s (FEV₁) values increased in the regular group 1 year after the initiation of therapy, but they decreased in the irregular group. At year 15, the predicted FEV₁% had decreased significantly more in the irregular group than in the regular group (p < 0.05); FEV₁ decreased by 28.2 ml/year (SD 24.5) in the regular group and by 44.6 ml/year (32.5) in the irregular group (p < 0.05). The decrease in FEV₁ was greater in smokers than in nonsmokers, despite regular ICS treatment, and it was significantly greater in patients with severe asthma than in those with mild or intermittent disease. Delay in ICS initiation also affected the annual FEV₁ decrease. Conclusions: Regular ICS, introduced early when symptoms are mild, could prevent lung function from worsening significantly. Smoking should be strongly discouraged in asthma patients.