Chest
Volume 136, Issue 3, September 2009, Pages 716-725
Journal home page for Chest

Original Research
COPD
Chronic Bronchitis, COPD, and Lung Function in Farmers: The Role of Biological Agents

https://doi.org/10.1378/chest.08-2192Get rights and content

Background

Farmers have an increased risk of respiratory morbidity and mortality. The causal agents have not been fully established.

Methods

In a cross-sectional study of 4,735 Norwegian farmers, we assessed respiratory symptoms and lung function. Atopy was assessed in a subsample (n = 1,213). Personal exposures to dust, fungal spores, actinomycete spores, endotoxins, bacteria, storage mites, (1→3)-ß-D-glucans, fungal antigens, organic dust, inorganic dust, silica, ammonia, and hydrogen sulfide were measured for 127 randomly selected farms.

Results

Compared to crop farmers, livestock farmers were more likely to have chronic bronchitis (odds ratio [OR], 1.9; 95% confidence interval [CI], 1.4 to 2.6) and COPD (OR, 1.4; 95% CI, 1.1 to 1.7). FEV1 (−41 mL; 95% CI, −75 to −7) was significantly reduced, but FVC (−15 mL; 95% CI, −54 to 24) was not. Exposure to most agents were predictors of respiratory morbidity, except FVC. Ammonia, hydrogen sulfide, and inorganic dust were most strongly associated in multiple regression models adjusted for coexposures, but the effects of specific biological agents could not be assessed in multiple regression models because they were too highly correlated. Farmers with atopy had a significantly lower FEV1 (OR, −87 mL; 95% CI, −170 to −7), but atopy was not directly associated with chronic bronchitis, COPD, and FVC. However, the effects of farming and specific exposures on COPD were substantially greater in farmers with atopy.

Conclusions

Livestock farmers have an increased risk of chronic bronchitis, COPD, and reduced FEV1. Ammonia, hydrogen sulfide, inorganic dust, and organic dust may be causally involved, but a role for specific biological agents cannot be excluded. Farmers with atopy appear more susceptible to develop farming-related COPD.

Section snippets

Study Population

Farmers from southeast Norway and spouses engaged in farming (all called farmers hereafter) were selected from the Norwegian government's Register of Farmers. A total of 8,482 farmers participated in medical examinations during 1991,12 which included spirometry, blood sampling, and a questionnaire (participation rate, 79%). Atopy was assessed in a hierarchical stratified sample based on self-reported ever-asthma, chronic bronchitis, COPD, work-related mucous membrane irritations, and no

Results

The population characteristics are summarized in Table 1 and annual exposure levels in Table 2. The levels of agents with occupational exposure limits (OELs) were generally below the Norwegian OELs. However, fungal spore levels exceeded the risk levels published in a recent criteria document,28 and in most cases, endotoxin levels exceeded the proposed OEL for endotoxins in the Netherlands.29 Only minor differences in exposure levels were found between men and women (data not shown). Many agents

Discussion

Livestock farmers had significantly higher prevalence of chronic bronchitis and COPD than crop farmers; FEV1 was lower, but no significant difference was observed for FVC. Duration of farming was associated with significant reductions both in FEV1 and FVC. All types of livestock farmers had elevated risks of chronic bronchitis. Dairy farmers had significantly increased COPD. Farmers raising more than one type of livestock had significantly increased risks of chronic bronchitis and COPD, and

Acknowledgments

Author contributions: Dr. Eduard performed the study, wrote the manuscript, and performed the statistical analysis. Dr. Pearce participated in the strategy of the statistical analysis and contributed to the manuscript. Dr. Douwes analyzed the samples for endotoxins, glucans, and EPS Asp/Pen antigens, participated in the statistical analysis, and wrote parts of the manuscript.

Financial/nonfinancial disclosures: The authors have reported to the ACCP that no significant conflicts of interest exist

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Support/Funding: This project was financially supported by the Agricultural Research Council of Norway, the Agricultural Agreement Research Fund, the Agricultural Investment Fund, Norske Meierier (Norwegian Dairies), Gjensidige (insurance company), and Forenede (insurance company). Pharmacia Diagnostics supplied the reagents for the Phadebas Phadiatop and specific IgE tests, and Nycomed Pharma performed the RAST analyses. The Centre for Public Health Research is supported by a Programme Grant from the Health Research Council (HRC) of New Zealand.

Reproduction of this article is prohibited without written permission from the American College of Chest Physicians (www.chestjournal.org/site/misc/reprints.xhtml).

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