Evaluation of psychological and physiological predictors of fatigue in patients with COPD

BACKGROUND: Fatigue in COPD impairs functional status; however there are few studies examining mechanistic pathways of this symptom. The aims of this study are to compare fatigue between COPD patients and healthy age-matched subjects, and to identify predictors of fatigue in COPD. METHODS: Seventy four COPD patients, mean age 69.9 (49-87) yrs, mean (SD) % predicted FEV(1 )46.5 (20.0) % and FEV(1)/FVC ratio 0.45 (0.13) and 35 healthy subjects, mean age 67.1 (50-84) yrs completed the Multidimensional Fatigue Inventory (MFI 20). Patients' assessment included Depression (HADS), lung function, BMI, muscle strength, incremental shuttle walk test (ISWT), exercise oxygen saturation (SpO(2)), Borg breathlessness (CR-10) and exertion (RPE). Serum level of Interleukin 6 (IL-6) was recorded. Differences in MFI 20 between groups were examined and predictors of fatigue identified using logistic regression. RESULTS: Significant differences (p < 0.01) were found between the COPD and healthy subjects for all MFI 20 dimensions. There were significant differences when classified according to GOLD and dyspnoea stages for selected dimensions only. Predictors of General Fatigue were depression, muscle strength and end SpO(2 )(R(2 )= .62); of Physical Fatigue: depression, % predicted FEV(1), ISWT and age (R(2 )= .57); Reduced Activity: % predicted FEV(1), BMI and depression (R(2 )= .36); Reduced Motivation: RPE, depression and end SpO(2 )(R(2 )= .37) and Mental Fatigue: depression and end SpO(2 )(R(2 )= .38). CONCLUSION: All dimensions of fatigue were higher in COPD than healthy aged subjects. Predictive factors differ according to the dimension of fatigue under investigation. COPD-RF is a multi component symptom requiring further consideration.