title: Factors associated with experience of fatigue, and functional limitations due to fatigue in patients with stable COPD.
abstract: The aim of this study was to determine the influence of selected physiological, psychological and situational factors on experience of fatigue, and functional limitations due to fatigue in patients with stable chronic obstructive pulmonary disease (COPD).
  
  
  
  In total 101 patients with COPD and 34 control patients were assessed for experience of fatigue, functional limitation due to fatigue (Fatigue Impact Scale), physiological [lung function, 6-minute walk distance (6MWD), body mass index (BMI), dyspnoea, interleukin (IL)-6, IL-8, high sensitivity C-reactive protein (hs-CRP), surfactant protein D], psychological (anxiety, depression, insomnia), situational variables (age, sex, smoking, living alone, education), and quality of life.
  
  
  
  Fatigue was more common in patients with COPD than in control patients (72% versus 56%, p < 0.001). Patients with COPD and fatigue had lower lung function, shorter 6MWD, more dyspnoea, anxiety and depressive symptoms, and worse health status compared with patients without fatigue (all p < 0.01). No differences were found for markers of systemic inflammation. In logistic regression, experience of fatigue was associated with depression [odds ratio (OR) 1.69, 95% confidence interval (CI) 1.28-2.25) and insomnia (OR 1.75, 95% CI 1.19-2.54). In linear regression models, depression, surfactant protein D and dyspnoea explained 35% (R(2)) of the variation in physical impact of fatigue. Current smoking and depression explained 33% (R(2)) of the cognitive impact of fatigue. Depression and surfactant protein D explained 48% (R(2)) of the psychosocial impact of fatigue.
  
  
  
  Experiences of fatigue and functional limitation due to fatigue seem to be related mainly to psychological but also to physiological influencing factors, with depressive symptoms, insomnia problems and dyspnoea as the most prominent factors. Systemic inflammation was not associated with perception of fatigue but surfactant protein D was connected to some dimensions of the impact of fatigue.
authors: Department of Medicine, Division of Pulmonology, Ryhov County Hospital, Jönköping, Sweden, S-551 85 Jönköping, Sweden and Department of Medical and Health Sciences, Linköping University, S-581 83 Linköping, Sweden magnus.kentson@rjl.se.
authors: Magnus
authors: M
authors: Kentson
authors: Department of Respiratory Medicine, Linköping University, Linköping, Sweden and Department of Respiratory Medicine & Allergology, Skane University Hospital, Lund, Sweden.
authors: Kristina
authors: K
authors: Tödt
authors: Department of Medical and Health Sciences, Linköping University, Linköping, Sweden.
authors: Elisabeth
authors: E
authors: Skargren
authors: Department of Medicine, Division of Pulmonology, Ryhov County Hospital, Jönköping, Sweden.
authors: Per
authors: P
authors: Jakobsson
authors: Department of Clinical Immunology and Transfusion Medicine, Clinical Immunology, Linköping, Sweden.
authors: Jan
authors: J
authors: Ernerudh
authors: Department of Social and Welfare Studies, Linköping University, Norrköping, Sweden.
authors: Mitra
authors: M
authors: Unosson
authors: Faculty of Health, Science and Technology, Department of Health Sciences, Nursing, Karlstad University and Primary Care Research Unit, County Council of Värmland, Karlstad, Sweden.
authors: Kersti
authors: K
authors: Theander
mesh_terms: D000368:Aged; D001007:Anxiety / Q000453:epidemiology / Q000209:etiology; D016022:Case-Control Studies; D003430:Cross-Sectional Studies; D003863:Depression / Q000453:epidemiology / Q000209:etiology; D004417:Dyspnea / Q000453:epidemiology / Q000209:etiology; D005080:Exercise Test; D005221:Fatigue / Q000453:epidemiology / Q000209:etiology* / Q000523:psychology; D005260:Female; D006304:Health Status; D006801:Humans; D007249:Inflammation / Q000453:epidemiology / Q000209:etiology; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D029424:Pulmonary Disease, Chronic Obstructive / Q000453:epidemiology* / Q000503:physiopathology / Q000523:psychology; D011788:Quality of Life; D012907:Smoking / Q000453:epidemiology*
keywords: chronic obstructive pulmonary disease; fatigue; symptoms; systemic inflammation