Data Analysis
Data were analyzed using SPSS version 21. Characteristics of the sample were summarized using means and standard deviations for continuous variables and number and percentage of participants for categorical variables. Correlation analysis was performed to examine associations between depression, anxiety, measures of the social environment, and uncertainty. Two hierarchical linear regression models were used to examine the association between the social environment and uncertainty: one model for ambiguity and one for complexity. In both models, demographic and medical characteristics were entered as a first step (i.e., age, gender, education, lifetime tobacco exposure, genotype, number of years since COPD diagnosis, oxygen use, augmentation therapy use, and exacerbations in the prior year). Symptoms of depression and anxiety were entered as a second step. The measures of the social environment were added as a third step to examine the extent to which the social environment is associated with uncertainty after adjusting for (1) demographic and medical characteristics and (2) depression and anxiety. Significance tests were two-sided with a significance level of 0.05