The fatigue suffered by patients with rheumatoid arthritis (RA) reflects pain and depression rather than disease activity, report researchers in the UK.
The study of over 500 RA patients has also shown that reported fatigue fell after successful treatment with disease-modifying antirheumatic drugs (DMARDs) and anti-tumor necrosis factor (anti-TNF).
Clinically relevant fatigue is common in RA, affecting 40–80% of patients attending specialist clinics, says the team from Kings College London. However, with less than 5% of RA patients in remission reporting the symptom, disease activity has been suspected as a causal factor in RA fatigue.
To investigate, Louise Pollard and colleagues assessed two cohorts of 238 and 274 RA patients for fatigue using visual analogue scores (VAS) and Medical Outcomes Study Short Form 36 vitality scores. The disease activity score for 28 joints and its components was also recorded.
Over 80% of the patients had clinically relevant disease, defined as a VAS of 20 mm or more, with more than 50% showing high levels of VAS of 50 mm or more, note the researchers in an early online edition of the journal Rheumatology.
Multiple regression analysis showed that pain had the strongest association with fatigue in both cohorts, followed by health assessment questionnaire outcomes and depression.
Additionally, responses in 54 patients starting therapy with DMARDs for at least 6 months and in 30 patients beginning anti-TNF treatment for 3 months or more were assessed.
Before treatment, 87% of patients had high levels of fatigue, but afterwards, this fell to 50%. The researchers say that these treatment effects were mainly linked to improvements in pain.
"In conclusion, high fatigue levels are common in RA and are mainly linked to pain and depression," note Pollard et al. "The association with disease activity is secondary."
They add: "The balance of evidence suggests that fatigue is centrally mediated in established RA."