title: 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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: From the National Research Centre for the Working Environment; Faculty of Health and Medical Sciences, Institute for Clinical Medicine, University of Copenhagen; Department of Public Health, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen; The DANBIO Database, Center for Rheumatology and Spine Diseases, Rigshospitalet; Copenhagen Center for Arthritis Research, Center for Rheumatology and Spine Diseases, Rigshospitalet, Glostrup; Department of Occupational Medicine, Slagelse Hospital, Slagelse, Denmark; Optum Patient Insights, Lincoln, Rhode Island, USA.S.M. Hansen, PhD Student, National Research Centre for the Working Environment, and the DANBIO Database, Center for Rheumatology and Spine Diseases, Rigshospitalet, and Copenhagen Center for Arthritis Research, Center for Rheumatology and Spine Diseases, Rigshospitalet; M.L. Hetland, MD, PhD, Professor, the DANBIO Database, Center for Rheumatology and Spine Diseases, Rigshospitalet, and Faculty of Health and Medical Sciences, Institute for Clinical Medicine, University of Copenhagen, and Copenhagen Center for Arthritis Research, Center for Rheumatology and Spine Diseases, Rigshospitalet; J. Pedersen, PhD, Statistician, National Research Centre for the Working Environment; M. Østergaard, PhD, Professor, Faculty of Health and Medical Sciences, Institute for Clinical Medicine, University of Copenhagen, and Copenhagen Center for Arthritis Research, Center for Rheumatology and Spine Diseases, Rigshospitalet; T.S. Rubak, MD, PhD, Department of Occupational Medicine, Slagelse Hospital; J.B. Bjorner, PhD, Professor, National Research Centre for the Working Environment, and Optum Patient Insights, and Faculty of Health and Medical Sciences, Department of Public Health, University of Copenhagen. smh@nrcwe.dk.
authors.forename: Sofie Mandrup
authors.initials: SM
authors.lastname: Hansen
authors.affiliation: From the National Research Centre for the Working Environment; Faculty of Health and Medical Sciences, Institute for Clinical Medicine, University of Copenhagen; Department of Public Health, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen; The DANBIO Database, Center for Rheumatology and Spine Diseases, Rigshospitalet; Copenhagen Center for Arthritis Research, Center for Rheumatology and Spine Diseases, Rigshospitalet, Glostrup; Department of Occupational Medicine, Slagelse Hospital, Slagelse, Denmark; Optum Patient Insights, Lincoln, Rhode Island, USA.S.M. Hansen, PhD Student, National Research Centre for the Working Environment, and the DANBIO Database, Center for Rheumatology and Spine Diseases, Rigshospitalet, and Copenhagen Center for Arthritis Research, Center for Rheumatology and Spine Diseases, Rigshospitalet; M.L. Hetland, MD, PhD, Professor, the DANBIO Database, Center for Rheumatology and Spine Diseases, Rigshospitalet, and Faculty of Health and Medical Sciences, Institute for Clinical Medicine, University of Copenhagen, and Copenhagen Center for Arthritis Research, Center for Rheumatology and Spine Diseases, Rigshospitalet; J. Pedersen, PhD, Statistician, National Research Centre for the Working Environment; M. Østergaard, PhD, Professor, Faculty of Health and Medical Sciences, Institute for Clinical Medicine, University of Copenhagen, and Copenhagen Center for Arthritis Research, Center for Rheumatology and Spine Diseases, Rigshospitalet; T.S. Rubak, MD, PhD, Department of Occupational Medicine, Slagelse Hospital; J.B. Bjorner, PhD, Professor, National Research Centre for the Working Environment, and Optum Patient Insights, and Faculty of Health and Medical Sciences, Department of Public Health, University of Copenhagen.
authors.forename: Merete Lund
authors.initials: ML
authors.lastname: Hetland
authors.affiliation: From the National Research Centre for the Working Environment; Faculty of Health and Medical Sciences, Institute for Clinical Medicine, University of Copenhagen; Department of Public Health, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen; The DANBIO Database, Center for Rheumatology and Spine Diseases, Rigshospitalet; Copenhagen Center for Arthritis Research, Center for Rheumatology and Spine Diseases, Rigshospitalet, Glostrup; Department of Occupational Medicine, Slagelse Hospital, Slagelse, Denmark; Optum Patient Insights, Lincoln, Rhode Island, USA.S.M. Hansen, PhD Student, National Research Centre for the Working Environment, and the DANBIO Database, Center for Rheumatology and Spine Diseases, Rigshospitalet, and Copenhagen Center for Arthritis Research, Center for Rheumatology and Spine Diseases, Rigshospitalet; M.L. Hetland, MD, PhD, Professor, the DANBIO Database, Center for Rheumatology and Spine Diseases, Rigshospitalet, and Faculty of Health and Medical Sciences, Institute for Clinical Medicine, University of Copenhagen, and Copenhagen Center for Arthritis Research, Center for Rheumatology and Spine Diseases, Rigshospitalet; J. Pedersen, PhD, Statistician, National Research Centre for the Working Environment; M. Østergaard, PhD, Professor, Faculty of Health and Medical Sciences, Institute for Clinical Medicine, University of Copenhagen, and Copenhagen Center for Arthritis Research, Center for Rheumatology and Spine Diseases, Rigshospitalet; T.S. Rubak, MD, PhD, Department of Occupational Medicine, Slagelse Hospital; J.B. Bjorner, PhD, Professor, National Research Centre for the Working Environment, and Optum Patient Insights, and Faculty of Health and Medical Sciences, Department of Public Health, University of Copenhagen.
authors.forename: Jacob
authors.initials: J
authors.lastname: Pedersen
authors.affiliation: From the National Research Centre for the Working Environment; Faculty of Health and Medical Sciences, Institute for Clinical Medicine, University of Copenhagen; Department of Public Health, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen; The DANBIO Database, Center for Rheumatology and Spine Diseases, Rigshospitalet; Copenhagen Center for Arthritis Research, Center for Rheumatology and Spine Diseases, Rigshospitalet, Glostrup; Department of Occupational Medicine, Slagelse Hospital, Slagelse, Denmark; Optum Patient Insights, Lincoln, Rhode Island, USA.S.M. Hansen, PhD Student, National Research Centre for the Working Environment, and the DANBIO Database, Center for Rheumatology and Spine Diseases, Rigshospitalet, and Copenhagen Center for Arthritis Research, Center for Rheumatology and Spine Diseases, Rigshospitalet; M.L. Hetland, MD, PhD, Professor, the DANBIO Database, Center for Rheumatology and Spine Diseases, Rigshospitalet, and Faculty of Health and Medical Sciences, Institute for Clinical Medicine, University of Copenhagen, and Copenhagen Center for Arthritis Research, Center for Rheumatology and Spine Diseases, Rigshospitalet; J. Pedersen, PhD, Statistician, National Research Centre for the Working Environment; M. Østergaard, PhD, Professor, Faculty of Health and Medical Sciences, Institute for Clinical Medicine, University of Copenhagen, and Copenhagen Center for Arthritis Research, Center for Rheumatology and Spine Diseases, Rigshospitalet; T.S. Rubak, MD, PhD, Department of Occupational Medicine, Slagelse Hospital; J.B. Bjorner, PhD, Professor, National Research Centre for the Working Environment, and Optum Patient Insights, and Faculty of Health and Medical Sciences, Department of Public Health, University of Copenhagen.
authors.forename: Mikkel
authors.initials: M
authors.lastname: Østergaard
authors.affiliation: From the National Research Centre for the Working Environment; Faculty of Health and Medical Sciences, Institute for Clinical Medicine, University of Copenhagen; Department of Public Health, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen; The DANBIO Database, Center for Rheumatology and Spine Diseases, Rigshospitalet; Copenhagen Center for Arthritis Research, Center for Rheumatology and Spine Diseases, Rigshospitalet, Glostrup; Department of Occupational Medicine, Slagelse Hospital, Slagelse, Denmark; Optum Patient Insights, Lincoln, Rhode Island, USA.S.M. Hansen, PhD Student, National Research Centre for the Working Environment, and the DANBIO Database, Center for Rheumatology and Spine Diseases, Rigshospitalet, and Copenhagen Center for Arthritis Research, Center for Rheumatology and Spine Diseases, Rigshospitalet; M.L. Hetland, MD, PhD, Professor, the DANBIO Database, Center for Rheumatology and Spine Diseases, Rigshospitalet, and Faculty of Health and Medical Sciences, Institute for Clinical Medicine, University of Copenhagen, and Copenhagen Center for Arthritis Research, Center for Rheumatology and Spine Diseases, Rigshospitalet; J. Pedersen, PhD, Statistician, National Research Centre for the Working Environment; M. Østergaard, PhD, Professor, Faculty of Health and Medical Sciences, Institute for Clinical Medicine, University of Copenhagen, and Copenhagen Center for Arthritis Research, Center for Rheumatology and Spine Diseases, Rigshospitalet; T.S. Rubak, MD, PhD, Department of Occupational Medicine, Slagelse Hospital; J.B. Bjorner, PhD, Professor, National Research Centre for the Working Environment, and Optum Patient Insights, and Faculty of Health and Medical Sciences, Department of Public Health, University of Copenhagen.
authors.forename: Tine Steen
authors.initials: TS
authors.lastname: Rubak
authors.affiliation: From the National Research Centre for the Working Environment; Faculty of Health and Medical Sciences, Institute for Clinical Medicine, University of Copenhagen; Department of Public Health, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen; The DANBIO Database, Center for Rheumatology and Spine Diseases, Rigshospitalet; Copenhagen Center for Arthritis Research, Center for Rheumatology and Spine Diseases, Rigshospitalet, Glostrup; Department of Occupational Medicine, Slagelse Hospital, Slagelse, Denmark; Optum Patient Insights, Lincoln, Rhode Island, USA.S.M. Hansen, PhD Student, National Research Centre for the Working Environment, and the DANBIO Database, Center for Rheumatology and Spine Diseases, Rigshospitalet, and Copenhagen Center for Arthritis Research, Center for Rheumatology and Spine Diseases, Rigshospitalet; M.L. Hetland, MD, PhD, Professor, the DANBIO Database, Center for Rheumatology and Spine Diseases, Rigshospitalet, and Faculty of Health and Medical Sciences, Institute for Clinical Medicine, University of Copenhagen, and Copenhagen Center for Arthritis Research, Center for Rheumatology and Spine Diseases, Rigshospitalet; J. Pedersen, PhD, Statistician, National Research Centre for the Working Environment; M. Østergaard, PhD, Professor, Faculty of Health and Medical Sciences, Institute for Clinical Medicine, University of Copenhagen, and Copenhagen Center for Arthritis Research, Center for Rheumatology and Spine Diseases, Rigshospitalet; T.S. Rubak, MD, PhD, Department of Occupational Medicine, Slagelse Hospital; J.B. Bjorner, PhD, Professor, National Research Centre for the Working Environment, and Optum Patient Insights, and Faculty of Health and Medical Sciences, Department of Public Health, University of Copenhagen.
authors.forename: Jakob Bue
authors.initials: JB
authors.lastname: Bjorner
mesh_terms: D000293:Adolescent; D000328:Adult; D001172:Arthritis, Rheumatoid; D015331:Cohort Studies; D003718:Denmark; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012042:Registries; D018582:Sick Leave; D013997:Time Factors; D016526:Workload; D055815:Young Adult
keywords: COHORT STUDY; COX PROPORTIONAL HAZARDS MODEL; EMPLOYEE WORK LOAD; REGISTRY; RHEUMATOID ARTHRITIS; SICK LEAVE