Thyroid function within the normal range, subclinical hypothyroidism and the risk of atrial fibrillation

Baumgartner, C. et al. (2017) Thyroid function within the normal range, subclinical hypothyroidism and the risk of atrial fibrillation. Circulation, 136(22), pp. 2100-2116. (doi: 10.1161/CIRCULATIONAHA.117.028753) (PMID:29061566)

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Abstract

Background -Atrial fibrillation (AF) is a highly prevalent disorder leading to heart failure, stroke, and death. Enhanced understanding of modifiable risk factors may yield opportunities for prevention. The risk of AF is increased in subclinical hyperthyroidism, but it is uncertain whether variations in thyroid function within the normal range or subclinical hypothyroidism are also associated with AF. Methods -We conducted a systematic review and obtained individual participant data from prospective cohort studies that measured thyroid function at baseline and assessed incident AF. Studies were identified from MEDLINE and EMBASE databases from inception to July 27, 2016. The euthyroid state was defined as thyroid-stimulating hormone (TSH) 0.45 to 4.49 mIU/L, and subclinical hypothyroidism as TSH 4.5 to 19.9 mIU/L with free thyroxine (fT4) levels within reference range. The association of TSH levels in the euthyroid and subclinical hypothyroid range with incident AF was examined by using Cox proportional hazards models. In euthyroid participants, we additionally examined the association between fT4 levels and incident AF. Results -Of 30 085 participants from 11 cohorts (278 955 person-years of follow-up), 1958 (6.5%) had subclinical hypothyroidism and 2574 individuals (8.6%) developed AF during follow-up. TSH at baseline was not significantly associated with incident AF in euthyroid participants or those with subclinical hypothyroidism. Higher fT4 levels at baseline in euthyroid individuals were associated with increased AF risk in ageand sex-adjusted analyses (hazard ratio, 1.45; 95% confidence interval, 1.26-1.66, for the highest quartile versus the lowest quartile of fT4; P for trend ≤0.001 across quartiles). Estimates did not substantially differ after further adjustment for preexisting cardiovascular disease. Conclusions -In euthyroid individuals, higher circulating fT4 levels, but not TSH levels, are associated with increased risk of incident AF.

Item Type:Articles
Keywords:Atrial fibrillation, free thyroxine, subclinical hypothyroidism, thyroid hormones, thyroid stimulating hormone.
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Macfarlane, Professor Peter and Stott J, Professor David
Authors: Baumgartner, C., da Costa, B. R., Collet, T.-H., Feller, M., Floriani, C., Bauer, D. C., Cappola, A. R., Heckbert, S. R., Ceresini, G., Gussekloo, J., den Elzen, W. P.J., Peeters, R. P., Luben, R., Völzke, H., Dörr, M., Walsh, J. P., Bremner, A., Iacoviello, M., Macfarlane, P., Heeringa, J., Stott, D. J., Westendorp, R. G.J., Khaw, K.-T., Magnani, J. W., Aujesky, D., and Rodondi, N.
College/School:College of Medical Veterinary and Life Sciences > Institute of Cardiovascular and Medical Sciences
College of Medical Veterinary and Life Sciences > Institute of Health and Wellbeing > Robertson Centre
Journal Name:Circulation
Publisher:American Heart Association
ISSN:0009-7322
ISSN (Online):1524-4539
Published Online:23 October 2017
Copyright Holders:Copyright © 2017 American Heart Association, Inc
First Published:First published in Circulation 136(22):2100-2116
Publisher Policy:Reproduced in accordance with the copyright policy of the publisher

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