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The spectrum of thyroid disease and risk of new onset atrial fibrillation: a large population cohort study

BMJ 2012; 345 doi: http://dx.doi.org/10.1136/bmj.e7895 (Published 27 November 2012) Cite this as: BMJ 2012;345:e7895
  1. Christian Selmer, research fellow1,
  2. Jonas Bjerring Olesen, research fellow1,
  3. Morten Lock Hansen, research fellow1,
  4. Jesper Lindhardsen, research fellow1,
  5. Anne-Marie Schjerning Olsen, research fellow1,
  6. Jesper Clausager Madsen, research fellow2,
  7. Jens Faber, professor34,
  8. Peter Riis Hansen, research director1,
  9. Ole Dyg Pedersen, research fellow5,
  10. Christian Torp-Pedersen, professor14,
  11. Gunnar Hilmar Gislason, research director1
  1. 1Department of Cardiology, Gentofte University Hospital, Hellerup, Denmark
  2. 2Copenhagen General Practitioners Laboratory, Copenhagen, Denmark
  3. 3Department of Endocrinology, Herlev University Hospital, Herlev, Denmark
  4. 4Faculty of Health Sciences, University of Copenhagen, Denmark
  5. 5Department of Cardiology, Roskilde University Hospital, Copenhagen, Denmark
  1. Correspondence to: C Selmer cselmer{at}gmail.com
  • Accepted 5 November 2012

Abstract

Objectives To examine the risk of atrial fibrillation in relation to the whole spectrum of thyroid function in a large cohort of patients.

Design Population based cohort study of general practice patients identified by linkage of nationwide registries at the individual level.

Setting Primary care patients in the city of Copenhagen.

Subjects Registry data for 586 460 adults who had their thyroid function evaluated for the first time by their general practitioner during 2000-10 and who were without previously recorded thyroid disease or atrial fibrillation.

Main outcome measure Poisson regression models used to estimate risk of atrial fibrillation by thyroid function.

Results Of the 586 460 individuals in the study population (mean (SD) age 50.2 (16.9) years, 39% men), 562 461 (96.0%) were euthyroid, 1670 (0.3%) had overt hypothyroidism, 12 087 (2.0%) had subclinical hypothyroidism, 3966 (0.7%) had overt hyperthyroidism, and 6276 (1.0%) had subclinical hyperthyroidism. Compared with the euthyroid individuals, the risk of atrial fibrillation increased with decreasing levels of thyroid stimulating hormone (TSH) from high normal euthyroidism (incidence rate ratio 1.12 (95% CI 1.03 to 1.21)) to subclinical hyperthyroidism with reduced TSH (1.16 (0.99 to 1.36)) and subclinical hyperthyroidism with supressed TSH (1.41 (1.25 to 1.59)). Both overt and subclinical hypothyroidism were associated with a lower risk of atrial fibrillation.

Conclusion The risk of atrial fibrillation was closely associated with thyroid activity, with a low risk in overt hypothyroidism, high risk in hyperthyroidism, and a TSH level dependent association with risk of atrial fibrillation across the spectrum of subclinical thyroid disease.

Footnotes

  • Contributors: CS made primary contributions to data collection and analysis, interpretation of results, and writing the manuscript. GHG and ODP helped to write the first draft. JBO, GHG, MLH, ODP, JL, and CT-P contributed to the study conception and design. All authors contributed to interpretation of results, all revised the manuscript critically for important intellectual content, and all approved the final manuscript. CS is the guarantor.

  • Funding: The study was partly funded by unrestricted grants from the Danish Heart Foundation (No 11-04-R84-A3483-22669), Danish Thyroid Association, Agnes and Knut Mørk Foundation, and FUKAP and START Foundations, Gentofte University Hospital, Denmark.

  • Competing interests: All authors have completed the ICMJE uniform disclosure form at www.icmje.org/coi_disclosure.pdf (available on request from the corresponding author) and declare: no support from any organisation for the submitted work; no financial relationships with any organisations that might have an interest in the submitted work in the previous three years; no other relationships or activities that could appear to have influenced the submitted work.

  • Ethical approval: Retrospective register studies do not require ethical approval in Denmark. This study was approved by the Danish Data Protection Agency (reference 2007-41-1667). All authors had full access to the data and take full responsibility for their integrity.

  • Data sharing: No additional data available.

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