title: Subjective fatigue, influencing variables, and consequences in chronic obstructive pulmonary disease.
abstract: 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.
  
  
  OBJECTIVE
  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 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, which 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 quality 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.
authors.affiliation: College of Nursing, Department of Medical-Surgical Nursing, University of Illinois at Chicago, IL 60612-7350, USA. mkapel1@uic.edu
authors.forename: Mary C
authors.initials: MC
authors.lastname: Kapella
authors.forename: Janet L
authors.initials: JL
authors.lastname: Larson
authors.forename: Minu K
authors.initials: MK
authors.lastname: Patel
authors.forename: Margaret K
authors.initials: MK
authors.lastname: Covey
authors.forename: Jean K
authors.initials: JK
authors.lastname: Berry
mesh_terms: D000203:Activities of Daily Living; D000339:Affect; D000368:Aged; D000704:Analysis of Variance; D001007:Anxiety / Q000209:etiology; D001294:Attitude to Health; D015992:Body Mass Index; D003430:Cross-Sectional Studies; D003863:Depression / Q000209:etiology; D004417:Dyspnea / Q000209:etiology; D005221:Fatigue / Q000145:classification / Q000209:etiology* / Q000523:psychology*; D005260:Female; D005541:Forced Expiratory Volume; D006801:Humans; D008297:Male; D008875:Middle Aged; D008960:Models, Psychological; D029424:Pulmonary Disease, Chronic Obstructive / Q000150:complications*; D011788:Quality of Life; D012307:Risk Factors; D012720:Severity of Illness Index; D012893:Sleep Wake Disorders / Q000209:etiology; D011795:Surveys and Questionnaires