Within-Day Variability of Fatigue and Pain among African Americans and Non-Hispanic Whites with Osteoarthritis of the Knee

Abstract

Objective Fatigue is common among persons with osteoarthritis (OA), but little is known about racial/ethnic differences in the prevalence, correlates, or dynamics of fatigue in OA. This research therefore used experience sampling methodology (ESM) to examine fatigue and pain at global and momentary levels among African Americans and non-Hispanic whites with OA. Methods Thirty-nine African Americans and 81 non-Hispanic whites with physician-diagnosed knee OA completed a baseline interview and an ESM protocol assessing fatigue, pain, and mood 4 times daily for 7 days. In addition to analyzing basic group differences, multilevel modeling examined within- versus between-subject patterns and correlates of variability in momentary fatigue, controlling for demographics and other potential confounders. Results Both racial groups experienced moderate levels of fatigue; however, there were clear individual differences in both mean fatigue level and variability across momentary assessments. Mean fatigue levels were associated with global pain and depression. Increase in fatigue over the course of the day was much stronger among non-Hispanic whites than African Americans. Momentary fatigue and pain were closely correlated. Mean fatigue predicted variability in mood; at the momentary level, both fatigue and pain were independently associated with mood. Conclusion Fatigue is a significant factor for both African Americans and non-Hispanic whites with OA, and is negatively related to quality of life. Pain symptoms, at both the momentary level and across individuals, were robust predictors of fatigue. Although overall levels of reported symptoms were similar across these 2 groups, the pattern of fatigue symptoms across the day differed.