Estimating the Extent and Distribution of New-Onset Adult Asthma in British Columbia Using Frequentist and Bayesian Approaches

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Jeremy Beach1,*, Igor Burstyn1,2 and Nicola Cherry1

1Department of Medicine, University of Alberta, Edmonton, Alberta T6G 2T4, Canada

2Department of Environmental and Occupational Health, School of Public Health, Drexel University, Philadelphia, PA 19102, USA ?* Author to whom correspondence should be addressed. Tel: +1-780-492-6291; fax: +1-780-492-9677; e-mail: jeremy.beach{at}ualberta.ca Received September 26, 2011. Accepted January 14, 2012. Introduction: We previously described a method to identify the incidence of new-onset adult asthma (NOAA) in Alberta by industry and occupation, utilizing Workers’ Compensation Board (WCB) and physician billing data. The aim of this study was to extend this method to data from British Columbia (BC) so as to compare the two provinces and to incorporate Bayesian methodology into estimates of risk.

Methods: WCB claims for any reason 1995–2004 were linked to physician billing data. NOAA was defined as a billing for asthma (ICD-9 493) in the 12 months before a WCB claim without asthma in the previous 3 years. Incidence was calculated by occupation and industry. In a matched case-referent analysis, associations with exposures were examined using an asthma-specific job exposure matrix (JEM). Posterior distributions from the Alberta analysis and estimated misclassification parameters were used as priors in the Bayesian analysis of the BC data. Results: Among 1?118?239 eligible WCB claims the incidence of NOAA was 1.4%. Sixteen occupations and 44 industries had a significantly increased risk; six industries had a decreased risk. The JEM identified wood dust [odds ratio (OR) 1.55, 95% confidence interval (CI) 1.08–2.24] and animal antigens (OR 1.66, 95% CI 1.17–2.36) as related to an increased risk of NOAA. Exposure to isocyanates was associated with decreased risk (OR 0.57, 95% CI 0.39–0.85). Bayesian analyses taking account of exposure misclassification and informative priors resulted in posterior distributions of ORs with lower boundary of 95% credible intervals >1.00 for almost all exposures. Conclusions: The distribution of NOAA in BC appeared somewhat similar to that in Alberta, except for isocyanates. Bayesian analyses allowed incorporation of prior evidence into risk estimates, permitting reconsideration of the apparently protective effect of isocyanate exposure. © The Author 2012. Published by Oxford University Press on behalf of the British Occupational Hygiene SocietyThis ArticleAnn Occup Hyg (2012) 56 (6): 719-727. doi: 10.1093/annhyg/mes004 First published online: February 29, 2012 Current Issue
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Posted in: Adult, Approaches, Asthma, Bayesian, British, Columbia, Distribution, Estimating, Extent, Frequentist, NewOnset, Using