Study rationale: The main risk factors of COPD are tobacco smoking, biomass smoking and occupational factors. Tobacco smoking is well-known risk factor so tobacco induced COPD is completely established. Nevertheless the meaning of occupational factors which are less famous are equally important. Based on comprehensive literature review American Thoracic Society (ATS) endorsed the notion that strong evidence implicates occupational factors as cause of COPD \[Eisner MD et al., 2010\]. Occupational COPD takes 19.2 % of all COPD patients and 31.1 % of never smokers as resulted NHANESIII study \[Hnizdo E. et al., 2004\]. A considerable number of work-related factors have evidence for a causal association with COPD including (and of course not limited) silica and silicates and polycyclic aromatic hydrocarbons. Individuals in a variety of occupations and industries such as coal miners, coke workers, tunnel workers, metallurgists, welding workers, transportation workers, builders, farmers are exposed to factors cited above. Despite this the clinical and pathophysiological features of COPD caused by occupational factors are still unclear.
Occupational factors leading airflow limitation are various entities - vapors, dusts, gases and fumes with different physical, chemical, biological and other features, so the mechanisms underlying disease development and progression may be different attributable to risk factor.
An environmental risk factors exposure as well as tobacco smoking results in COPD only in part of the subjects which indicates the significant genome and gene environmental interactions role. COPD develops in predisposed subjects undergoing risk factors exposure. Therefore the risk of COPD is individual and depends on both genetic and environments. There are few data concerning the effects of genetic on COPD risk in this specific subgroup - people who are exposed to occupational risk factors related to the certain environmental factor.
Statistical analysis: Statistical analysis will be carried out by Statistica 9.0 software. Significance level will be considered p = 0.05. The qualitative variables will be expressed as counts and percentages. The quantitative continuous variables will be expressed as means and standard error of means (M ± m) for variables that meet the criteria of normality and minimum and maximum, median for those that do not meet the criteria of normality. Kruskal-Wallis test will be used for comparing multiply independent samples and Mann-Whitney U test for comparing two independent samples if variable under consideration will continuous and that it will be measured on an ordinal scale. For comparisons of proportions, the Chi-square will be used.
For associations assessment logistic regression method will be used. The odds ratio (OR) and 95% confidence interval (CI) will be calculated for each professional group. Multiple regression model will be used to explore the relationships between demographic characteristics, cytokine concentrations, hemostasis and airflow limitation in professional groups.
