A significant 30% reduction in the number of sick leave days used per month was seen in adults with rheumatoid arthritis after using tumor necrosis factor antagonists for 6 months.
The finding was observed in a population-based study of 365 RA patients aged 18-85 years.
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The study is among the first to address the quantitative impact of TNF inhibitors on sick leave and disability pension, said Dr. Tor Olofsson of Lund (Sweden) University, and colleagues, whose study was published in the December issue of Annals of the Rheumatic Diseases.
They reviewed insurance database information on RA patients enrolled in the South Swedish Arthritis Treatment Group registry. Each patient was matched with four controls from the general population.
The study population averaged 9 sick days per month in the first month of anti-TNF treatment. The monthly rate dropped to an average of 6.5 days after 6 months and remained steady at an average of 6.6 days per month for months 6-12 (Ann. Rheum. Dis. 2010;69:2131-6).
Compared with the controls in the general population, the relative risk of being on sick leave in the RA group was 6.6 at the start of treatment, but dropped to 5.1 after 6 months, and remained at an average of 5.2 for the rest of the year. The relative risk of being on disability pension was 3.4 at the start of treatment and 3.2 after 1 year of treatment.
Approximately 98% of the patients had tried at least one disease-modifying antirheumatic drug (DMARD) before starting anti-TNF therapy. The average age of the patients was 46 years, and 82% were women. A total of 92 patients (25%) discontinued treatment, including 34 for adverse events, 32 for treatment failure, and 26 for other reasons.
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"The reduction in sick leave during the first anti-TNF treatment year must be considered as a conservative measure in this cohort of patients who were severely ill, since there was a steady increase in sick leave prior to initiation of therapy," the researchers wrote. "Even a stabilization of the sick leave level could have been deemed as a successful outcome," they noted.
The results support findings from previous studies of the effects of TNF inhibitors on work outcomes, although the study was limited by the short follow-up period, the researchers noted. The findings conflict with data from a recent observational study that showed no difference in employment loss between RA patients using anti-TNF therapy and controls. However, the average duration of RA in the observational study was 12 years, compared to an average duration of 4.5 years in the current study. This difference suggests a possible protective effect from anti-TNF therapy in a subset of patients with less than 11 years disease duration at the start of therapy, the researchers said.
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The researchers said that they had no relevant financial conflicts to disclose. The study was funded by grants from multiple nonpharmaceutical organizations including the Swedish Research Council, Lund University, Region Skåne, the Swedish Social Insurance Agency, the Swedish Rheumatism Association, and the King Gustav V 80-Year Fund.