title: Inflammatory lung disease a potential risk factor for onset of idiopathic inflammatory myopathies: results from a pilot study.
abstract: OBJECTIVE
  To assess the association between inflammatory lung disease and the risk of developing idiopathic inflammatory myopathies.
  
  
  METHODS
  A population-based case-control study was conducted. Adult myositis cases, identified from the Swedish inpatient registry (diagnosed between 1995 and 1997), and randomly selected controls matched to cases on the date of birth, gender and residency, were asked to fill out a questionnaire with questions on lifestyle, environmental exposures and health. Eventually, 100 cases and 402 controls responded to the questionnaire and were included in the analyses. Exposure was defined as self-reported preceding inflammatory lung diseases (pneumonia, tuberculosis or sarcoidosis). The association between the exposure and risk of developing myositis was evaluated by calculating OR together with 95% CIs in logistic regressions.
  
  
  RESULTS
  42 (42%) cases and 112 (28%) controls reported preceding inflammatory lung disease. Median duration between inflammatory lung disease and first symptom of myositis was 30 years. We observed a significant association between self-reported history of lung disease at study inclusion and diagnosis of myositis (crude OR=1.8 (1.1 to 2.9); smoking adjusted OR=1.9 (1.2 to 3.1)). We further identified a modestly increased, yet non-significant, association between preceding inflammatory lung disease (prior to index year) and diagnosis of myositis (smoking adjusted OR=1.6 (0.9 to 2.8)). The association was more pronounced among the cases of myositis with concurrent interstitial lung disease (OR=3.8 (1.0 to 14.5)).
  
  
  CONCLUSIONS
  Patients with preceding inflammatory lung disease tend to have an increased risk of developing myositis compared to those without. The effect was more pronounced among patients with myositis with concurrent interstitial lung disease. Thus inflammatory lung disease may constitute a risk factor for myositis.
authors.affiliation: Unit of Cardiovascular Epidemiology , Karolinska Institutet, Institute of Environmental Medicine , Stockholm , Sweden.
authors.forename: Sevim Barbasso
authors.initials: SB
authors.lastname: Helmers
authors.affiliation: Unit of Cardiovascular Epidemiology , Karolinska Institutet, Institute of Environmental Medicine , Stockholm , Sweden.
authors.forename: Xia
authors.initials: X
authors.lastname: Jiang
authors.affiliation: Unit of Cardiovascular Epidemiology , Karolinska Institutet, Institute of Environmental Medicine , Stockholm , Sweden.
authors.forename: David
authors.initials: D
authors.lastname: Pettersson
authors.affiliation: Department of Medicine, Rheumatology Unit , Karolinska Institutet, Karolinska University Hospital , Stockholm , Sweden.
authors.forename: Anna-Lis
authors.initials: AL
authors.lastname: Wikman
authors.affiliation: Unit of Cardiovascular Epidemiology , Karolinska Institutet, Institute of Environmental Medicine , Stockholm , Sweden.
authors.forename: Pia
authors.initials: P
authors.lastname: Axelman
authors.affiliation: Department of Medicine, Rheumatology Unit , Karolinska Institutet, Karolinska University Hospital , Stockholm , Sweden.
authors.forename: Åsa
authors.initials: Å
authors.lastname: Lundberg
authors.affiliation: Department of Medicine, Rheumatology Unit , Karolinska Institutet, Karolinska University Hospital , Stockholm , Sweden.
authors.forename: Ingrid E
authors.initials: IE
authors.lastname: Lundberg
authors.affiliation: Unit of Cardiovascular Epidemiology, Karolinska Institutet, Institute of Environmental Medicine, Stockholm, Sweden; Centre for Occupational and Environmental Medicine, Stockholm County Council, Stockholm, Sweden.
authors.forename: Lars
authors.initials: L
authors.lastname: Alfredsson
keywords: Dermatomyositis; Epidemiology; Infections; Polymyositis