Fatigue Affects Work Disability in Rheumatoid Arthritis, Ankylosing Spondylitis

Fatigue had a significant and independent effect on work disability measures in rheumatoid arthritis and ankylosing spondylitis.

In patients with rheumatoid arthritis (RA) or ankylosing spondylitis (AS) starting etanercept therapy, fatigue significantly and independently affected work disability measures over the course of a year, according to findings published in Arthritis Research & Therapy.

Although biologic therapies have improved outcomes for inflammatory rheumatic diseases, patients continue to experience considerable work disability. Fatigue is a prevalent symptom that is suspected of contributing to work impairment, but evidence is limited. This was the first study to examine the relationship between fatigue and work disability in 2 distinct rheumatic conditions.

Researchers analyzed data from 2 separate observational studies following patients with AS and RA (ClinicalTrials.gov identifiers: NCT00544557) and NCT00488475). Those with AS starting etanercept therapy (n=1003; mean age, 40.7 years; 36.7% women; mean disease duration, 7.3 years) and those with RA starting etanercept therapy (n=1747; mean age, 47.3 years; 72.4% female, mean disease duration, 7.9 years) were followed for 1 year, with assessments at baseline and at 6 and 12 months.

Baseline variables considered potential predictors, including fatigue, were recorded and work disability measures were evaluated at each visit. Fatigue was indicated by means of a visual analogue scale and work disability was evaluated using the Work Productivity and Activity Impairment-Special Health Problems inventory, which contains 4 subscales.

In participants with AS, there was a significant association between fatigue and both presenteeism (β=3.75; 95% CI, 2.14-5.36) and activity impairment (β=2.62; 95% CI, 1.26-3.98), but not between fatigue and work productivity loss (β=1.81; 95% CI, -0.40 to 4.02) or absenteeism (odds ratio [OR], 1.18; 95% CI, 0.92-1.51).

Individuals with RA demonstrated significant associations between fatigue and presenteeism (β=3.44; 95% CI, 2.17-4.70), activity impairment (β=1.52; 95% CI, 0.79-2.26), work productivity loss (β=4.16; 95% CI, 2.47-5.85), and absenteeism (OR, 1.23; 95% CI, 1.02-1.49). There were no significant associations between baseline fatigue and visit, which indicated a consistent effect of fatigue over time. Baseline measures of anxiety and depression also appeared to significantly and negatively affect work disability metrics.

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Researchers noted that participants were starting biologic medications and may not be representative of the larger AS and RA populations. Other study limitations included potential nongeneralizability secondary to cultural differences; lack of a control group, limiting quantification of etanercept effect; noninclusion of some potentially useful variables regarding sleep, medications, and severity; the observational design, which prevents causality inference; and use of only global nonspecific psychosocial measures.

Fatigue had a significant effect on work disability measures over 12 months in patients with AS or RA, but to somewhat different extents. The investigators recommended that future studies use alternative fatigue measures in varied sampling frames and suggest that, “fatigue-alleviating interventions such as cognitive behavioural therapy and exercise should be tested in [those with] both RA and AS.”

Disclosures: This study was supported by Pfizer. The sponsor was involved in the study design, collection, analysis, and interpretation of data, as well as revising the manuscript for intellectual content.

NB has received research funding and lecture fees from Pfizer. MD, LA, and PS are employees of Pfizer and hold company stock or shares. AB is an employee of Quanticate and is a paid contractor to Pfizer. KLD declares that she has no competing interests.

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Druce KL, Aikman L, Dilleen M, Burden A, Szczypa P, Basu N. Fatigue independently predicts different work disability dimensions in etanercept-treated rheumatoid arthritis and ankylosing spondylitis patients. Arthritis Res Ther. 2018;20(1):96.