Participants
The research was conducted in the outpatient clinics of the department for chest diseases of a university hospital in east Turkey. The inclusion criteria were COPD of at least duration of 6 months or longer, residence in the city,
absence of a disease diagnosis additional to COPD, ability to read and write and willingness to collaborate. To prevent selection bias, all eligible patients received a number according to their application to the departmental clinic for chest diseases. Odd-numbered patients were placed in one group; even-numbered patients were placed in the second group. Participant recruitment continued until we achieved two similar groups according to demographic features.