Abstract
To determine predictors of longitudinal changes in pulmonary function in swine confinement workers. Longitudinal study conducted from November 1989 to June 1991 and January 1994 to May 1995. Swine confinement workers in Saskatchewan. Forty-two swine confinement workers who were studied in 1989/90 and studied again in 1994/95. Of 98 male swine confinement workers (mean age SD 36.3 11.1 years) studied at baseline, 42 were studied again five years following. Complete information on baseline across-shift pulmonary function (preshift forced expiratory volume in 1 s [FEV1], forced vital capacity [FVC], and every 2 h FEV1 and FVC during the shift), and five-year follow-up pulmonary function (with FEV1 and FVC) were available on all 42 subjects. Mean across-shift changes (preshift measurement to last measurement of the day) at baseline were -159. 8 61.7 mL in FEV1 and -35.3 65.6 mL in FVC. Mean annual rate change between baseline and follow-up for FEV1 was -53.9 61.7 mL/year and for FVC -48.9 71.6 mL/year. After adjusting for age, height, smoking and hours spent in the barn, the baseline across-shift change in FEV1 and FVC was a significant predictor of annual rate change in FEV1 (P=0.01) and FVC (P=0.02), respectively. To determine the effects of indoor air quality on longitudinal lung function decline, indoor air environmental measurements were analysed. Complete information on respiratory health and indoor air quality was available on 34 of the 42 subjects. Assessment of indoor environment of swine barns included a summer and winter measurement for airborne dust, gases and endotoxin levels. After adjusting for age, height, smoking, ammonia and hours spent in the barn, the endotoxin level (Eu/mg)was a significant predictor of annual rate change for FEV1 but not FVC. These results suggest that shift change is an important predictor of longitudinal changes in lung function in swine confinement workers and that endotoxin exposures may mediate annual decline in FEV1 in these workers.
Highlights
It seems relatively well established that swine confinement workers suffer yearly reductions in lung function test variables that are in excess of those observed in nonexposed, nonfarming control subjects
Both previous smoking status and concentrations of ambient air contaminants are potential determinants in annual decline in both forced expired volume in 1 s (FEV1) and forced vital capacity (FVC), while age is an important predictor of annual loss in FEV1; shift change at baseline evaluation is the predictor of the annual rate change in both FEV1 and FVC that emerges as the most powerful in both models
These findings raise the possibility that, if shift change at one point in time could be used to predict longitudinal decline in excess of that seen in nonexposed control subjects [13], shift change could be used to predict which workers might be prone to development of future losses in lung function and possibly airflow limitation [20]
Summary
A recent study reported a dose-response relationship between across-shift changes in lung function in swine farmers, and endotoxin and ammonia levels in the confinement units [16]. We report the results of our investigations on the relationship between shift change and longitudinal decline in lung function measurements, and between environmental exposure to air contaminants and longitudinal decline in lung function measurements among swine confinement workers in Canada.
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