Abstract

BACKGROUND: There are few reports about longitudinal changes in lung function in asthmatic patients. Patients with asthma had a greater loss of lung function than normal healthy adults. To date, there have been no studies about the longitudinal changes in lung function in patients with occupational asthma. METHODS: 280 male patients with red cedar asthma (RCA) who were followed up for at least one year were the study group. The exposed controls consisted of 399 male sawmill workers. Forced expiratory volume in one second (FEV1) was measured with a Collins water spirometer. Changes in FEV1 over time (FEV1 slope) were calculated by a two point method for each subject. Atopy was considered to be present if the subjects showed at least one positive response to three allergens by skin prick test. RESULTS: Multiple regression analysis was carried out to examine factors that might affect longitudinal decline in FEV1. Patients with RCA who were still exposed had a greater decline in FEV1 slope (-26 ml/y) than sawmill workers. Smokers also showed a greater rate of decline in FEV1 (-43 ml/y) than non-smokers. CONCLUSIONS: Patients with RCA who continued to be exposed had a greater rate of decline in FEV1 than sawmill workers. Early diagnosis of occupational asthma and removal of these patients from a specific sensitiser is important in the prevention of further deterioration of lung function and respiratory symptoms.