The association of dyspnea and fatigue severity with physical activity and physical capacity in patients with COPD

BACKGROUND: It is well-established that dyspnea and fatigue are barriers to physical activity (PA) and have a negative effect on physical capacity (PC) in individuals with chronic obstructive pulmonary disease (COPD). However, it remains unclear how those symptoms interact on physical function and whether one holds dominance over the other. AIM: To compare physical activity and physical capacity of individuals with COPD with different severities of fatigue and dyspnea symptoms, and to identify the dominant limiting symptom of physical function. METHODS: In this cross-sectional study, individuals with COPD visiting an outpatient clinic were assessed for dyspnea (mMRC dyspnea) and fatigue (CIS-Fatigue). Key outcomes were PC (six-minute walk distance, 6MWD) and daily PA (steps/day). Individuals were stratified into four groups based on severe dyspnea (yes/no, mMRC dyspnea ≥2) and/or severe fatigue (yes/no, CIS-Fatigue ≥36 points). RESULTS: 58±18) were analyzed and classified as: Low dyspnea/low fatigue (LD/LF n=186, 34%), low dyspnea/severe fatigue (LD/SF, n=123, 22%), severe dyspnea/low fatigue (SD/LF, n=71, 13%), severe dyspnea/severe fatigue (SD/SF, n=169, 31%). The groups SD/LF and SD/SF had significantly worse 6MWD (413±94 and 376±107 meters, respectively) and lower levels of daily PA (4183[2382-6087] and 3470[2114-5056] steps/day, respectively) when compared to the LD/LF and LD/SF groups (479±75 and 475±93 meters; 6466[4587-8094] and 5830[4041-7889] steps/day, respectively) (p<.005). CONCLUSION: Individuals with COPD who experience severe dyspnea consistently exhibit worse levels of daily PA and PC compared with those who report low dyspnea, regardless of the presence or not of severe fatigue.