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The link between fatigue and disease activity in inflammatory arthritis appears not to be as simple as previously assumed.
Minnock P, McKee G, Bresnihan B, et al.How much is Fatigue Explained by Standard Clinical Characteristics of Disease Activity in Patients with Inflammatory Arthritis: A Longitudinal Study. Arthritis Care & Research (2014) Accepted manuscript. doi: 10.1002/acr.22387
Patients with inflammatory arthritis (IA) often say that their fatigue improves dramatically after starting TNF inhibitors (TNFi), the authors of this article observe. But the assumption that fatigue relates directly to disease activity has never been tested, they add, which led them to launch this study, which found something quite different.
It tracked fatigue prospectively among 125 patients with active IA starting TNFi therapy at a large academic medical center in Dublin. The results show that fatigue is taken into account least when the disease is most active, and seems to relate to “a variety of biobehavioral variables.”
Those variables may include pain, sleep, mood, and self-efficacy, the authors note-none of which is related directly to disease activity.
Most of the patients were women in their 50s, who had had rheumatoid arthritis (70%) or psoriatic arthritis (30%) for a mean of almost 12 years. Previous synthetic disease-modifying anti-rheumatic drug (sDMARD) therapy had failed for 66% of patients. More than half were taking adalimumab (Humira), almost 40% used etanercept (Enbrel), and the remainder were on infliximab (Remicade).
Prior to starting TNFis, the patients reported high levels of fatigue. At 3 months, fatigue had improved by 35%, and by 29% at 6 months. Mean scores on the 50-point multidimensional assessment of fatigue scale (MAF) dropped from 27.4 at baseline to 17.9 at 3 months, and was at 19.5 at 6 months.
Disease activity, assessed according to several standard measures, also improved significantly during that time. However, early changes in fatigue were related more directly to the health assessment questionnaire (HAQ) and the global health (GH) assessment than to disease activity alone, the researchers note.
Thus the handy presumption that improving disease activity will resolve fatigue appearas to be disproven. After stabilizing the disease, these authors conclude, medication probably won't achieve further improvements in fatigue. It seems to require addressing interventions that can resolve cognitive, behavioral, and personal issues.