Effect of Rheumatoid Arthritis on Longterm Sickness Absence in 1994-2011: A Danish Cohort Study

Abstract

Objective.By linkage of national registries, we investigated the risk of longterm sickness absence (LTSA) ≥ 3 weeks in a large cohort of Danish patients with rheumatoid arthritis (RA) and non-patients. The study aimed to (1) estimate the risk of LTSA for patients with RA compared with the general population, (2) examine whether the risk of LTSA has changed in recent years, and (3) evaluate the effect of other risk factors for LTSA (e.g., physical work demands, age, sex, education, and psychiatric and somatic comorbidities).Methods.A total of 6677 patients with RA aged 18–59 years in the years 1994–2011 were identified in registries and compared with 56,955 controls from the general population matched by age, sex, and city size. The risk of LTSA was analyzed using Cox proportional hazards models with late entry, controlling for other risk factors and assuming separate risks in the first year after diagnosis and the following years.Results.Compared with the general population, patients with RA had increased risk of LTSA in the first year after diagnosis (HR 5.4 during 1994–1999, 95% CI 4.2–6.8) and in following years (HR 2.4, 95% CI 2.1–2.8). For established RA (> 1 yr after diagnosis), the excess was 20% lower in 2006–2011 (HR 1.9, 95% CI 1.7–2.2) compared with 1994–1999 (p < 0.001). For patients with RA and controls, older age, shorter education, a physically demanding job, and somatic and/or psychiatric comorbidities increased the risk of LTSA.Conclusion.While improvements were observed from 1994–1999 to 2006–2011, patients with RA have significant increased risk of LTSA, in particular in the first year after diagnosis.