title: Extra-articular disease manifestations in rheumatoid arthritis: incidence trends and risk factors over 46 years.
abstract: OBJECTIVE
  To investigate the trends in incidence of extra-articular rheumatoid arthritis (ExRA) in a well defined community based cohort of patients with rheumatoid arthritis (RA), and to examine possible predictors of ExRA occurrence.
  
  
  METHODS
  Using the resources of the Rochester Epidemiology Project, a retrospective medical record review was conducted of a cohort of 609 cases of RA in Olmsted County, MN, diagnosed during 1955-94. These cases had been previously classified using the ACR 1987 criteria for RA. Patients were followed up from 1955 to 2000 (median follow up 11.8 years; range 0.1-42.8), and incident ExRA manifestations were recorded according to predefined criteria. Time to first presentation of ExRA was compared in patients with RA by decade of diagnosis. Possible ExRA risk factors were identified in case record reviews.
  
  
  RESULTS
  ExRA occurred in 247 patients (40.6%). A subgroup of 78 patients (12.8%) had ExRA manifestations considered to be severe in a previous study from Malmö, Sweden. The incidence of severe ExRA did not change significantly over the decades (p=0.165). In a multivariate analysis the main predictors of severe ExRA were smoking at RA diagnosis (risk ratio (RR)=2.94; 95% confidence interval (95% CI) 1.68 to 5.13) and early disability (Steinbrocker class III-IV at diagnosis) (RR=2.45; 95% CI 1.51 to 4.00). The effect of smoking overwhelmed the weaker effect of rheumatoid factor seropositivity.
  
  
  CONCLUSIONS
  There was no decrease in the incidence of extra-articular manifestations in patients with RA diagnosed up to 1995. Smoking and early disability are independent risk factors for extra-articular RA.
authors.affiliation: Department of Rheumatology, Malmö University Hospital, Lund University, Sweden. turesson.carl@mayo.edu
authors.forename: C
authors.initials: C
authors.lastname: Turesson
authors.forename: W M
authors.initials: WM
authors.lastname: O'Fallon
authors.forename: C S
authors.initials: CS
authors.lastname: Crowson
authors.forename: S E
authors.initials: SE
authors.lastname: Gabriel
authors.forename: E L
authors.initials: EL
authors.lastname: Matteson
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D001172:Arthritis, Rheumatoid / Q000150:complications*; D018572:Disease-Free Survival; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D008910:Minnesota / Q000453:epidemiology; D015999:Multivariate Analysis; D016016:Proportional Hazards Models; D011658:Pulmonary Fibrosis / Q000453:epidemiology / Q000209:etiology; D012189:Retrospective Studies; D012218:Rheumatoid Nodule / Q000453:epidemiology; D012307:Risk Factors; D012859:Sjogren's Syndrome / Q000453:epidemiology / Q000209:etiology; D012907:Smoking / Q000009:adverse effects