Table 4 Multivariate linear regression analysis for risk factors of increased SpCO (dependent variable) in participants without active smoking status (N = 808). The analysis was performed including the independent variables with a significance of p ≤ 0.1 from Table 3 (using the same nominal values for variables) as in univariate analysis: place of residence (urban/rural), passive exposure to cigarette smoking, place of cooking in household (cooking outside as reference category), cooking fuel / method of cooking (cooking with gas/electricity as reference category), biomass vs. non-biomass cooking fuel, occupational exposure to dusts vs. fumes (no exposure as reference category). A model was fitted using stepwise variable selection. The final model included the variables listed in the table

From: Symptoms and functional limitations related to respiratory health and carbon monoxide poisoning in Tanzania: a cross sectional study