title: The incidence and severity of rheumatoid arthritis, results from a county register in Oslo, Norway.
abstract: OBJECTIVE
  To examine the incidence of rheumatoid arthritis (RA) in the community of Oslo, Norway; and to link the incidence to measures of disease severity.
  
  
  METHODS
  A register for RA in the county of Oslo was validated to be 85% complete for patients between 20 and 79 years of age. The incidence of RA was calculated from this register for patients with disease onset 1988-1993 (n=550). Data on health related quality of life [Modified Health Assessment Questionnaire (MHAQ), Arthritis Impact Measurement Scale 2 (AIMS2), pain, fatigue] were obtained from a postal survey (response rate 73%).
  
  
  RESULTS
  The overall annual incidence of RA over a 6 year period was 25.7/100,000 (females 36.7, males 13.8). The incidence increased with age, from 7.8 in the age group 20-29 to 61.0 between 70 and 79 years. After 5 year followup a clinically important effect on physical function (MHAQ > 1.5) was seen in 38% of the patients, on social functioning (AIMS2 social > 4) in 50%, on mental distress (AIMS2 affect > 4) in 27%, on pain (VAS > 40 mm) in 35%, and on fatigue (VAS > 40 mm) in 41%.
  
  
  CONCLUSIONS
  The incidence of RA was 25.7/100,000 in the population of Oslo. After 5 years, 40-50% had clinically important changes in health status. The annual disease incidence with clinically important effect on physical function after 5 years was 10/100,000 individuals at risk.
authors.affiliation: Oslo City Department of Rheumatology, Diakonhjemmet Hospital, Olso, Norway.
authors.forename: T
authors.initials: T
authors.lastname: Uhlig
authors.forename: T K
authors.initials: TK
authors.lastname: Kvien
authors.forename: A
authors.initials: A
authors.lastname: Glennås
authors.forename: L M
authors.initials: LM
authors.lastname: Smedstad
authors.forename: O
authors.initials: O
authors.lastname: Førre
mesh_terms: D000328:Adult; D017677:Age Distribution; D000368:Aged; D001172:Arthritis, Rheumatoid / Q000453:epidemiology* / Q000503:physiopathology; D015331:Cohort Studies; D005260:Female; D006305:Health Status Indicators; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D009664:Norway / Q000453:epidemiology; D011788:Quality of Life; D012042:Registries; D012720:Severity of Illness Index; D017678:Sex Distribution; D011795:Surveys and Questionnaires