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Rheumatoid arthritis
Original research
Siblings of patients with rheumatoid arthritis have an increased mortality rate: a Swedish cohort study
  1. Helga Westerlind,
  2. Bénédicte Delcoigne and
  3. Johan Askling
  1. Department of Medicine, Solna, Karolinska Institutet, Stockholm, Sweden
  1. Correspondence to Helga Westerlind; Helga.Westerlind{at}ki.se

Abstract

Objectives To estimate the mortality among siblings of patients with rheumatoid arthritis (RA) and put any excess mortality among these in relation to the mortality among patients with RA.

Methods Using prospective nation-wide registers, we identified patients diagnosed with new-onset RA 2001–2017 (n=8137), patients with prevalent RA 2006–2017 (n=25 464), matched general population comparator subjects to all RA patients (n=22 457/68 674) and full-siblings of all groups (n=28 878/91 546).

We followed all cohorts until death, 31 December 2018, migration and (for non-RA subjects) RA diagnosis. We compared patients with RA versus the general population, and siblings of RA versus siblings of the general population using Cox regression, including adjustment for socio-economy.

Results The HR of death versus the general population was 1.11 (95% CI 1.01 to 1.22) for incident and 1.46 (95% CI 1.39 to 1.52) for prevalent patients with RA. The siblings of these patient groups were also at increased risk of death (HR=1.10, 95% CI 1.01 to 1.20 and 1.09, 95% CI 1.04 to 1.13, respectively), with little impact of adjustment for socio-economy.

Conclusion The mortality in RA is increased, but around one-fifth of this excess is present also among their siblings. Previous literature using general population rates for comparison has thus likely overestimated the direct impact on mortality attributable to RA. To bring down excess mortality in RA, optimal disease control is important but may not suffice.

  • Rheumatoid arthritis
  • Epidemiology
  • Treatment
  • Outcomes research
http://creativecommons.org/licenses/by-nc/4.0/

This is an open access article distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited, appropriate credit is given, any changes made indicated, and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/.

https://doi.org/10.1136/rmdopen-2020-001197

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    Footnotes

    • Contributors HW had full access to all of the data used for the analysis in this study and takes full responsibility for the integrity of the data and the accuracy of the data analysis. Study concept and design: JA, HW. Acquisition of data: JA, HW. Statistical analysis: HW, JA, BD. Analysis and interpretation of data: all authors. Drafting of manuscript: HW, JA. Critical revision of manuscript and final approval given: all authors. Obtained funding: JA. Study supervision: JA.

    • Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

    • Competing interests Karolinska Institutet (JA as principal investigator) has or has had research agreements with Abbvie, Astra-Zeneca, BMS, Eli Lilly, MSD, Pfizer, Roche, Samsung Bioepis, Sanofi and UCB, mainly in the context of safety monitoring of biologics via ARTIS/Swedish Biologics Register.

    • Patient consent Waived by the Region Stockholm Ethics Review Board because of the register-based setting.

    • Data sharing statement No data are available.

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