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Comparative Study
. 2012 Nov 27:345:e7895.
doi: 10.1136/bmj.e7895.

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

Affiliations
Comparative Study

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

Christian Selmer et al. BMJ. .

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.

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Conflict of interest statement

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.

Figures

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Fig 1 Flowchart of study cohort selection.
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Fig 2 Cumulative incidence of atrial fibrillation in relation to thyroid dysfunction at baseline thyroid screening (age >65 years). Values adjusted for competing risk of death from all causes
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Fig 3 Adjusted incidence rate ratios (box and whiskers) and unadjusted incidence rates per 1000 person years (bars) for atrial fibrillation by level of thyroid stimulating hormone (TSH) in euthyroid and subclinical hyperthyroid patients in study cohort

Comment in

References

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