BRONCHIAL RESPONSIVENESS AND 5-YEAR FEV1 DECLINE - A STUDY IN MINERS AND NONMINERS

Increased nonspecific bronchial responsiveness (NSBR) may be a risk fa ctor for the development of chronic airflow obstruction. We evaluated this hypothesis in a cohort of 378 underground coal miners and working nonminers. Methacholine testing was performed at the beginning and en d of a 5-yr study period. Spirometry was repeated at 6-mo intervals an d individual 5-yr FEV1 slopes were calculated by linear regression. Re lationships between FEV, slopes and NSBR were examined using multiple linear regression models, controlling for FEV1 level, smoking, and min ing. Increasing NSBR at the initial survey was associated with a somew hat greater rate of subsequent FEV1 decline. Methacholine responders a t the final survey had a considerably increased rate of decline during the previous years. Responsiveness status changed over the 5 yr in 22 % of the subjects. Both the development and persistence of increased N SBR were strongly associated with higher rates of FEV1 decline. In con trast, FEV, declines were not accelerated among workers with increased NSBR that reverted to normal. Smoking and mining were both independen tly associated with FEV1 declines, but did not substantially modify th e effect of NSBR. Due to its variability over time, NSBR testing predi cts lung function decline only in some individuals, and its value as a prognostic test for chronic airway disorders is limited. Because impr ovement in bronchial hyperresponsiveness was associated with a reducti on in the rate of FEV1 loss, interventions directed at preventing or r educing nonspecific airway hyperresponsiveness should be investigated.