title: Increased risk for chronic comorbid disorders in patients with inflammatory arthritis: a population based study.
abstract: BACKGROUND
  Studies determining the development of a wide variety of different comorbid disorders in inflammatory arthritis (IA) patients are scarce, however, this knowledge could be helpful in optimising preventive care in IA patients. The aim of this study is to establish the risk that new chronic comorbid disorders in newly diagnosed patients with IA in a primary care setting are developed.
  
  
  METHODS
  This is a nested-case-control study from 2001-2010 using data from electronic medical patient records in general practice. In total, 3,354 patients with newly diagnosed IA were selected. Each patient was matched with two control patients of the same age and sex in the same general practice. The development of 121 chronic comorbid disorders of index and control patients was compared using Cox regression.
  
  
  RESULTS
  After a median follow-up period of 2.8 years, 56% of the IA-patients had developed at least one chronic comorbid disorder after the onset of IA, compared to 46% of the control patients (p < 0.05). The most frequent developed comorbid disorders after the onset of IA were of cardiovascular (23%), and musculoskeletal (17%) origin. The highest hazard ratios (HRs) were found for anaemia (HR 2.0 [95% CI: 1.4-2.7]) osteoporosis (HR 1.9 [1.4-2.4]), and COPD (HR 1.8 [1.4-2.3]).
  
  
  CONCLUSIONS
  Patients with IA developed more chronic comorbid disorders after the onset of IA than one might expect based on age and sex. Since comorbidity has a large impact on the disease course, quality of life, and possibly on treatment itself, prevention of comorbidity should be one of the main targets in the treatment of IA patients.
authors.affiliation: NIVEL (Netherlands Institute for Health Services Research), PO Box 1568, Utrecht 3500, BN, the Netherlands. j.ursum@nivel.nl.
authors.forename: Jennie
authors.initials: J
authors.lastname: Ursum
authors.forename: Mark M J
authors.initials: MM
authors.lastname: Nielen
authors.forename: Jos W R
authors.initials: JW
authors.lastname: Twisk
authors.forename: Mike J L
authors.initials: MJ
authors.lastname: Peters
authors.forename: François G
authors.initials: FG
authors.lastname: Schellevis
authors.forename: Michael T
authors.initials: MT
authors.lastname: Nurmohamed
authors.forename: Joke C
authors.initials: JC
authors.lastname: Korevaar
mesh_terms: D000328:Adult; D000368:Aged; D000740:Anemia / Q000453:epidemiology*; D001172:Arthritis, Rheumatoid / Q000453:epidemiology*; D002318:Cardiovascular Diseases / Q000453:epidemiology*; D016022:Case-Control Studies; D002908:Chronic Disease; D015897:Comorbidity; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D009140:Musculoskeletal Diseases / Q000453:epidemiology; D010024:Osteoporosis / Q000453:epidemiology*; D016016:Proportional Hazards Models; D029424:Pulmonary Disease, Chronic Obstructive / Q000453:epidemiology*; D012307:Risk Factors; D025242:Spondylarthropathies / Q000453:epidemiology*