Determinants of fatigue among individuals with symptomatic knee osteoarthritis: the multicenter osteoarthritis study

Abstract

Purpose: Evidence regarding fatigue determinants in knee osteoarthritis (OA) is sparse. To gain greater understanding of fatigue aetiology in the OA population, more longitudinal studies with well-defined populations are warranted. The objective of the study was to identify sociodemographic, disease-related, physical and mental health-related determinants of generalised fatigue over a two-year follow-up among individuals with symptomatic knee osteoarthritis (OA). Methods: A longitudinal analysis of participants with symptomatic knee OA from the Multicenter Osteoarthritis Study (MOST) at the 60 months exam (here defined as baseline) was conducted to identify baseline predictors of fatigue at two-year follow-up. Symptomatic knee OA was defined as both the presence of radiographic whole knee OA and frequent knee pain at two different interviews at baseline. Only subjects with complete fatigue values at baseline and follow-up periods were included in the present study. Participants self-reported fatigue at baseline and at two-year follow-up using a 0-10 visual analogue scale. At baseline, questionnaires and/or examinations on sociodemographics (age, sex [men vs. women], race/ethnicity [white and caucasian vs. black and /or others], living situation [living alone vs. living with significant others], and monthly bill payment [no difficulty vs. difficulty/unable to pay monthly bills]), disease-related symptoms (sleep quality [poor vs. good], comorbidities, Western Ontario McMaster Universities Osteoarthritis index (WOMAC) pain, radiographic evidence of knee OA [KL score <2 vs. >2]), physical and mental health factors (Center for Epidemiologic Studies Depression Scale (CES-D), pain catastrophizing [<1 vs. >1], body mass index (BMI) and gait speed via 20 meter walk) were completed. Baseline fatigue was included as a predictor in the analysis. Data analysis was conducted using linear regressions with a backwards elimination approach. Results: Of the 2,330 individuals in the MOST cohort at baseline, 449 had symptomatic knee OA. The majority of participants included were women (64%) and white/caucasian (78%), had an average age of 66.27 [SD=7.85] years with baseline and follow-up fatigue scores of 3.91 [SD=2.45] and 3.70 [SD=2.37]. The final model showed that baseline fatigue (Unstandardized coefficient (B)=0.435; 95% confidence interval [CI] [0.348, 0.523]), slow gait speed (B=-1.124; 95% CI [-1.962, -0.285]), depressive symptoms (B=0.049; 95% CI [0.024, 0.075]) and higher numbers of comorbidities (B=0.242; 95% CI [0.045, 0.439]) were significant predictors of increased fatigue at follow-up. Conclusions: The result of this study indicated that higher pre-existing fatigue, lower physical function, higher depressive symptoms and increased comorbidities were determinants of fatigue longitudinally in those with symptomatic knee OA. Fatigue is strongly associated with modifiable physical and mental related health factors. In the light of these Results, combined targeted psychological and physical function rehabilitation might be modalities for generalised fatigue management in symptomatic knee OA.