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Résumé (français)

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Résumé (anglais)

Workers are being constantly subjected to different exposures at work, which are linked with their respiratory health. Typically, exposure to irritants, sensitizers, or toxic substances at the workplace can result in airway diseases. Understanding these associations will be beneficial in terms of prevention and mitigation of the effects of exposures. There are limited studies in the literature among the Canadian working population in this regard. The aim of this thesis is to examine the association between occupational/industrial exposures with asthma, respiratory symptoms and lung function in the Canadian working population. Data on 15-75 years old participants in the Canadian Health Measures Survey (CHMS) Cycle 1 (2007) & Cycle 2 (2009), a representative sample of Canadian population, were considered in the thesis. Exposure variables were defined by broad occupational categories and by industrial sectors based on National Occupational Classification – Statistics (NOC-S) 2001 and North American Industry Classification System (NAICS) 2002, respectively. Information on asthma and respiratory symptoms were collected using interviewer-administered questionnaires, and lung function parameters were measured according to the American Thoracic Society/European Respiratory Society guidelines for spirometry. Multiple logistic and linear regression analyses was used to characterize the association of occupational categories and industrial sectors with asthma and lung function parameters after controlling for potential confounders. There were significant differences in several characteristics between the employed and non-employed respondents (mean age: 39.9 vs. 52.5 years; female sex: 47% vs. 64%; post-secondary education: 61.0% vs. 44.5%; self-rated very good or excellent health: 57.0% vs. 41.0%; respectively). After adjusting for the potential confounders, the prevalence of cough with phlegm, shortness of breath and COPD was significantly lower in employed respondents in comparison to non-employed respondents. This pattern was reversed in the prevalence of current asthma with employed respondents reporting a greater prevalence than the non-employed respondents. After adjusting for potential confounders, the mean values of FVC, FEV1 and FEF25%-75% were significantly greater in employed than in non-employed respondents among both male and female participants. There were significant overall differences in several characteristics (age, sex, ethnicity, education and total personnel income, self-rated health, smoking and daily energy expenditure) of the respondents between both industrial sectors and broad occupational categories, respectively. No significant differences were observed between the industrial sectors in the prevalence of respiratory health outcomes among the respondents. Among the occupational categories, occupations unique to primary industry and occupations unique to processing, manufacturing and utilities had the highest prevalence for cough with phlegm (15%) with health occupations having the lowest prevalence (2.4%). Overall the differences between the occupational categories in the prevalence of cough and phlegm were statistically significant (p<0.05). After controlling for smoking status, no significant differences were observed in the mean values of percent-predicted FVC, FEV1 and FEV1/FVC of the respondents within either industrial sectors or broad occupational categories. After adjusting for potential confounders, the respondents in the industrial Sector 11 (Agriculture, Forestry, Fishing and Hunting/Mining, Oil and Gas Extraction/Utilities) were less likely to have current asthma in comparison to the respondents in the referent category (OR: 0.3; 95% CI: 0.1, 1.0; p=0.05). After adjusting for potential confounders, the respondents in the natural and applied science related occupations were more likely to have ever asthma in comparison to the respondents in the management occupations (OR: 2.1; 95% CI: 1.0, 4.5; p=0.05). After adjusting for potential confounders, the mean values of FVC and FEV1 in Sector 3 (arts, entertainment and recreation/accommodation and food services) were significantly lower than those in the referent category (Sector 1). Similarly, the mean value of FVC in Sector 8 (whole-sale trades/retail trade/ transportation and warehousing) was less than that in the referent category (p <0.05). The main findings from the thesis are (i) there is a gender disparity in the Canadian working population; (ii) the healthy worker effect is apparent among the working population and (iii) the respiratory health of the working population is related with some of the industrial sectors and broad occupational categories. Further exploration of the effects of employment on the respiratory health of the Canadian workers is needed and will be helpful in improving their respiratory health.