Background/Purpose: In a previous cross-sectional study we noted higher fatigue levels in patients with advanced lower limb OA compared with RA, and identified differences in common outcome variables and their associations with fatigue between RA and OA groups. High levels of disability and depression correlated with fatigue in both conditions. In the current longitudinal study, we re-appraised patients in the initial cohort and assessed their fatigue levels and associated disease variables 5 years after their initial assessment in order to test the stability of these influences over time.

Methods: The original study recruited 103 patients each with RA or hip/knee OA (n=206). Of these 68 OA and 72 with RA were available for re-assessment after 5 years (n=140; 68% retention). Reasons for loss to follow-up were moving out of area, death and declining to take part. All participants were assessed for pain and fatigue using 100mm VAS scales; functional disability using the HAQ- disability index; and mood using the Hospital Anxiety and Depression Scale (HADS-Anxiety and HADS-Depression). CRP was measured in all participants and BMI calculated. In the RA group, the Disease Activity Score (DAS-28) was recorded. In the OA group, pain and disability were self-reported using the WOMAC score. Changes over time in the outcomes of interest were assessed separately for OA and RA using paired t-tests. Changes were compared between OA and RA using regression models of follow-up values adjusting for baseline values of the variable in question, along with baseline age, sex, and BMI. Similar models were used to examine the impact of joint replacement within the OA group. Correlations between change scores for all outcomes were investigated separately for OA and RA using Pearson’s correlation coefficients.

Results: There was no evidence for interval changes over 5 years in RA for any of the outcomes including DAS-28 scores (change +0.00; 95% CI -0.33, 0.33; p=0.989) whereas in OA significant reductions in severity for a number of outcomes were recorded in the OA group: HAQ decreased by 0.38 (95% CI 0.20, 0.55; p<0.001), WOMAC-total by 21.6 points (95% CI 16.1, 27.1; p<0.001), pain (VAS) decreased by 27.1 (95% CI 19.4, 34.9; p<0.001), HADS-Depression decreased by 2.0 (95% CI 1.1, 2.9; p<0.001). In the OA group, changes between all 15 pairs of outcomes were positively correlated (p<0.045) aside from VAS fatigue and HAQ (p=0.087). However, there were fewer significant correlations in the RA group. Among the OA group, 57 (84%) had interval hip/knee joint replacement. There was no evidence that this was associated with better follow-up HAQ, pain, or fatigue (all unadjusted and adjusted p≥0.090), but was associated with improvement on WOMAC total (14.0 points unadjusted, 95% CI 1.0, 26.9; p=0.035; 13.8 adjusted, 0.9, 26.6; p=0.036).

Conclusion: After 5 years a range of common disease outcomes were surprisingly stable in RA, but significant reductions in pain, fatigue, disability and total WOMAC score were noted in OA, although only this last measure was associated with joint replacement. The strongest correlates with fatigue over 5 years were anxiety and depression in both groups.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/factors-affecting-interval-changes-in-perceived-fatigue-over-five-years-in-patients-with-rheumatoid-arthritis-compared-with-osteoarthritis/