“…In the present study, incapacity, handicap, and oxidative data of 2 groups (non-COPD and COPD smokers) were compared. Other studies have included 3 groups (COPD smokers, healthy smokers, and healthy non-smokers 16 or active and passive smokers and non-smokers 38 ). However, taking 3 groups into a single study seems to have little precedent in the literature and raises some questions, such as whether the prevalence of some clinical data (obesity, physical activity status, schooling level, socioeconomic level, clinical and pathological data) in the 3 groups is comparable.…”