Objective
Fatigue is a common symptom in systemic lupus erythematosus (SLE), and engaging in physical activity (PA) may reduce fatigue. We aimed to characterize relationships between fatigue, other health status measures assessed with the Patient Reported Outcomes Measurement Information System (PROMIS) instruments, and accelerometer-based PA measurements in patients with SLE. The internal consistency of each PROMIS measure in our SLE sample was also evaluated.
Methods
This cross-sectional study analyzed 123 adults with SLE. The primary fatigue outcome was Fatigue Severity Scale (FSS) score. Secondary outcomes were Patient Reported Outcomes Measurement Information System (PROMIS) standardized T-scores in seven health status domains. Accelerometers were worn for seven days, and mean daily minutes of light, moderate/vigorous, and bouted (10 minutes) moderate/vigorous PA were estimated. Cronbach’s alpha was determined for each PROMIS measure to assess internal consistency. Relationships between FSS, PROMIS, and PA were summarized with Spearman partial correlation coefficients (r), adjusted for average daily accelerometer wear time.
Results
Mean FSS (4.3, SD 1.6) was consistent with clinically relevant levels of fatigue. Greater daily and bouted moderate/vigorous PA minutes correlated with lower FSS (r=−0.20, p=0.03 and r=−0.30, p=0.0007, respectively). For PROMIS, bouted moderate/vigorous PA minutes correlated with less fatigue (r=−0.20, p=0.03). PROMIS internal consistency was excellent, with Cronbach’s alpha >0.90 for each domain. Mean PROMIS T-scores for fatigue, pain interference, anxiety, sleep disturbance, sleep-related impairment, and physical function were worse than reported for the general U.S. population. More moderate/vigorous PA minutes were associated with less pain interference (r=−0.22, p=0.01). Both light PA and moderate/vigorous PA minutes correlated with better physical function (r=0.19, p=0.04 and r=0.25, p=0.006, respectively).
Conclusion
More time spent in moderate/vigorous PA was associated with less fatigue (FSS and PROMIS), less pain interference, and better physical function (PROMIS). PROMIS had excellent internal consistency in our SLE sample, and six of seven PROMIS measures indicated poorer average health status in SLE patients compared to the general U.S. population.