Subjective fatigue, influencing variables, and consequences in chronic obstructive pulmonary disease

Background: Fatigue is a common symptom of chronic obstructive pulmonary disease (COPD), but little is known about the specific nature of COPD-related fatigue and its impact on daily life. Objectives: To (a) describe characteristics of fatigue in people with COPD and (b) test a theoretically and empirically supported model of the relationships among subjective fatigue, dyspnea, functional performance, anxious and depressed moods, and sleep quality in people with COPD. Methods: A cross-sectional descriptive study was conducted with 130 people with moderate to severe COPD. Measures 1 included the following: a Numerical Rating Scale (NRS) for frequency, intensity, and distress of fatigue and dyspnea; Fatigue Assessment Instrument (FAI); Chronic Respiratory Disease Questionnaire (CRQ); Profile of Mood States (POMS); Pittsburgh Sleep Quality Index (PSQI); Functional Performance Inventory (FPI); and spirometry. Path analysis was used to examine the relationships among variables. Results: Participants reported moderate amounts of fatigue, was described as situation-specific, had considerable consequences, and was responsive to rest and sleep. Dyspnea was slightly greater than fatigue, as measured by the NRSs (p <.001), and there was a strong relationship between fatigue and dyspnea (r=.74, p <.001). Dyspnea, depressed mood, and sleep quaity accounted for 42% of the variance in subjective fatigue. Fatigue, dyspnea, airflow obstruction, and anxious mood accounted for 36% of the variance in functional performance. Conclusions: Fatigue is an important problem that affects performance of daily activities in people with COPD. The relationships or interactions that exist among fatigue and other symptoms are complex.