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Mortality in idiopathic inflammatory myopathy: results from a Swedish nationwide population-based cohort study
  1. Gerd Cecilie Dobloug1,
  2. John Svensson2,
  3. Ingrid E Lundberg2,
  4. Marie Holmqvist2,3
  1. 1 Department of Rheumatology, Oslo University Hospital, Oslo, Norway
  2. 2 Rheumatology Unit, Department of Medicine, Karolinska Institutet, Karolinska University Hospital, Stockholm, Sweden
  3. 3 Unit of Clinical Epidemiology, Department of Medicine, Karolinska Institutet, Stockholm, Sweden
  1. Correspondence to Dr Marie Holmqvist, Unit of clinical epidemiology, Department of Medicine, Karolinska Institutet, T2, Karolinska Universitetssjukhuset, Stockholm 17176, Sweden; marie.holmqvist{at}ki.se

Abstract

Patients with idiopathic inflammatory myopathies (IIMs) suffer an increased burden of comorbidities, but data on mortality in recently diagnosed IIM are conflicting. Also, little is known when, if ever, in relation to IIM diagnosis, mortality is increased.

Methods A population-based IIM cohort of patients diagnosed between 2002 and 2011 and general population comparators were identified using healthcare registers. They were linked to the cause of death register for follow-up.

Results 224 (31%) of the 716 patients with IIM and 870 (12%) of the 7100 general population died during follow-up. This corresponded to a mortality rate of 60/1000 person-years in IIM and 20/1000 person-years in the general population. The cumulative mortality at 1 year after diagnosis was 9% in IIM and 1% in the general population, and increased in both IIM and the general population with time. The overall hazard ratio (HR) 95%CI of death comparing IIM with the general population was 3.7 (3.2 to 4.4). When we stratified on time since diagnosis, we noted an increase in mortality already within the first year of diagnosis compared with the general population, HR 9.6 (95% CI 6.9 to 13.5). This HR then plateaued around 2 after >10 years with the disease, although the estimates were not statistically significant. Malignancies, diseases of the circulatory and respiratory system were common causes of death.

Conclusion Mortality is increased in patients with contemporary IIM. The increased mortality was noted within a year of diagnosis, which calls for extra vigilance during the first year of IIM diagnosis.

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Footnotes

  • Contributors Study concept and design: MH, IEL and GCD. Acquisition of data: MH and IEL. Statistical analysis: MH. Analysis and interpretation of data, drafting of manuscript and critical revision of manuscript and final approval given: all authors. Obtained funding: IEL and MH. Study supervision: MH.

  • Funding The Swedish Research Council (Vetenskapsrådet), the Research Agreement on Medical Training and Clinical Research (ALF), Karolinska Institutet, the Swedish Rheumatism Association (Reumatikerförbundet) and the Swedish Society of Medicine (Svenska läkaresällskapet).

  • Competing interests IEL has received research grants from Astra-Zeneca and Bristol-Myers Squibb and has consultancies from Bristol-Myers Squibb and IDERA Pharmaceuticals. All other authors have declared no competing interests.

  • Patient consent This is a register-based study.

  • Ethics approval This study was approved by the Ethical Committee in Stockholm, Sweden.

  • Provenance and peer review Not commissioned; externally peer reviewed.

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