Objective: To investigate the relationship between the development of bronchitic symptoms and the early rapid decline of forced expiratory volume in 1 second (FEV1).
Methods: A two-stage and a mixed model approach were used to analyze data from 260 newly hired Chinese coal miners who completed approximately 5 to 16 health surveys during 3 years.
Results: The proportion of miners with onset of bronchitic symptoms was significantly elevated after 11 months of underground mining. Miners with incident symptoms had greater declines in FEV1 compared with those who did not (-65 vs -23 mL/yr, P < 0.05). At 24 months follow-up, FEV1 had declined an average 235 mL among the 26 miners who developed bronchitic symptoms and smoked, compared with a decline of 96 mL among the 132 nonsmoking miners without symptoms.
Conclusions: Among new coal miners, a sharp early decline in FEV1 is associated with the development of bronchitic symptoms.