Fatigue in the general Korean population: Application and normative data of the Brief Fatigue Inventory

The purpose of this study was to provide normative data for the Brief Fatigue Inventory (BFI) in the general Korean population so that the results for the general population could be compared with those for patients. We constructed a questionnaire that included the BFI and items on demographic characteristics and conducted a population-based, cross-sectional survey in 1,000 individuals. We used multivariate logistic analysis to investigate factors associated with usual and worst fatigue. The internal consistency was high (Cronbach's alpha = 0.96) and construct validity was confirmed by factor analysis. All patients had a mean +/- SD BFI score of 4.33 +/- 2.48 for worst fatigue and of 4.07 +/- 2.27 for usual fatigue, and the global BFI score was 3.44 +/- 2.05. The prevalence of each moderate-to severe fatigue type was similar in severity of fatigue, with 55.2% in usual fatigue, and 57.3% in worst fatigue. Among the types of fatigue, the prevalence of severe fatigue was lowest for usual fatigue (16.5%). In multivariate analysis, the group aged 40-59 years had greater levels of usual and worst fatigue compared with the group aged 20-29 years. Poor general health and the presence of comorbidities were also associated with increased usual and worst fatigue. Regular physical activity was associated with reduced levels of worst fatigue. The normal values of BFI with proper psychometric properties may help us to better understand the correlates of fatigue in the general population and patients. Our findings indicate that comorbidities should be considered when comparing fatigue data from the general population with data from patients.