Long-term deterioration of lung function in asthmatic outpatients

Background: Although the long-term deterioration of lung function in asthmatic patients has been described, the exact mechanism remains to be determined. Objectives: The aim of this study was to find correlations between age, sex, atopic status, duration of asthma, asthma severity and the decline in pulmonary function. Method: The medical histories of 1,006 randomly chosen asthmatic outpatients were studied and retrospective data on asthma duration, spirometry results, treatment and symptomatology were gathered. A screening spirometry was performed. Results: 598 women and 408 men (age: 44.59, range 12-95 years) participated in the study. Intermittent asthma was diagnosed in 35.4%, chronic mild asthma in 33.4%, moderate asthma in 23.8% and severe asthma in 7.45% of the patients. Statistically significant correlations between patient age, asthma duration and lung function measurements were found. Linear regression revealed the following differences in lung functions per year of asthma duration: FEV1: -0.882% of predicted; FVC: -0.509% of predicted; FEV1/FVC: -0.324% of predicted. The unadjusted annual decline was 80.1 ml/year (p = 0.00003) in FEV1 and 20.5 ml/year (p = 0.036) in FVC. A multiple regression model revealed that asthma severity appears to be the strongest factor influencing pulmonary function (beta = -0.55, p < 0.001 for FEV1). Also, significant associations between pulmonary function measurements, patient age, atopic status and male sex were noted. Conclusions: The results of this large cohort study show that asthmatic patients develop a progressive decline in pulmonary function correlated with age, sex, duration of asthma and asthma severity. Early diagnosis and intervention is necessary to ameliorate any potential negative impact of asthma on lung function. Copyright (C) 2004 S. Karger AG, Basel.