Article Text
Abstract
Objectives 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.
- Dermatomyositis
- Polymyositis
- Epidemiology
- Infections
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Footnotes
SB, XJ, IEL, LA authors contributed equally.
Contributors SBH, XJ and DP analysed the data, interpreted the results and drafted the manuscript; A-LW, PA and A-JL. interpreted the results and modified the manuscript. IEL and LA are the primary investigators of the EIRA study and provided important supports to carry out the study. All of the authors contributed significantly to the study design, data analysis, interpretation of results and manuscript writing.
Funding This study was supported by grants from the Swedish Research Council K2014-52X-14045-14-3, Sweden, Swedish Rheumatism Association, COMBINE, King Gustaf V 80-year Foundation, Institutet of Environmental Medicine, Theme Inflammation, and “The regional agreement on medical training and clinical research (ALF)” at Karolinska Institutet/Stockholm County Council, and Centre for Research and Development, Uppsala University/County Council of Gävleborg.
Competing interests None declared.
Patient consent Obtained.
Ethics approval The Ethics Committee of Karolinska University Hospital approved the study.
Provenance and peer review Not commissioned; externally peer reviewed.
Data sharing statement No additional data are available.