DETERMINANTS OF LONGITUDINAL CHANGES IN SPIROMETRIC FUNCTION AMONG SWINE CONFINEMENT OPERATORS AND FARMERS

To assess whether working in a swine confinement facility causes an ex cess or accelerated decline in lung function, we conducted a populatio n-based study to evaluate the determinants of longitudinal changes in airflow in a population of swine confinement operators. Spirometric me asures of lung function were compared between swine confinement operat ors(N = 168) and neighborhood farmer control subjects(N = 127). Study subjects were randomly selected from a cohort of swine confinement ope rators in eastern Iowa. The control farming population was matched by geographic location, age, and sex to the swine confinement operators. On average, the follow-up time was approximately 2 yr, with a range of follow-up between 56 and 1,900 d. Although swine confinement operator s and neighborhood farmers had similar demographic characteristics (ag e, gender, racial background, smoking history, and atopy status), swin e confinement operators tended to have less farming experience and wer e more extensively followed (more measures of lung function and longer periods of observation) than the neighborhood farmer control group. S wine confinement operators were also exposed to higher environmental d ust concentrations and other irritants than the farmer control subject s. Interestingly, the cross-sectional data indicated that swine confin ement operators tended to have slightly lower measures of airflow and greater workshift declines in forced expiratory volume in one second ( FEV(1)), forced vital capacity (FVC), and mid-expiratory flow (FEF(25- 75)) than the neighborhood farmer control group. After controlling for age, height, gender, cigarette smoking, and follow-up time, longitudi nal declines in spirometric measures of lung function were independent ly related to cross-shift declines in spirometric measures of lung fun ction (FEV(1), FVC, AND FEF(25-75)), higher concentrations of endotoxi n present in the bioaerosol (FEV(1) and FEF(25-75)), and working in th e swine confinement setting (FEV(1) and FEF(25-75)). Interestingly, cr oss-shift changes in lung function and higher concentrations of endoto xin in the bioaerosol interacted positively with follow-up time, indic ating that these work-related responses and exposures accelerated the decline in FEV(1) and FEF(25-75) during the period of observation. Our results indicate that cross-shift decrements in lung function and hig her concentrations of endotoxin are important determinants of accelera ted decrements in airflow among agricultural workers. Although work in the swine confinement setting was associated with lower measures of F EV(1) and FEF(25-75) that persisted throughout the period of observati on, work in these confinement facilities does not appear specifically to accelerate the progressive loss of lung function among agricultural workers.