Abstract 12505: New-onset Atrial Fibrillation is an Independent Long-term Risk-factor for Hyperthyroidism
Background: Hyperthyroidism is a well-known risk factor for atrial fibrillation (AF), but it is unknown whether new-onset AF predicts later-occurring hyperthyroidism.
Objectives: To examine the long-term risk of hyperthyroidism in patients admitted to hospital with new-onset AF.
Methods: All patients admitted with first-time AF in Denmark from 1997 to 2006 and their present and subsequent use of antithyroid medication were identified by individual-level linkage of nationwide registries of hospitalization and drug dispensing from pharmacies. Patients with previous thyroid disease or any thyroid medication were excluded. Development of hyperthyroidism was assessed by treatment initiation of methimazole or propylthiouracil within a 10 year period. Every patient was matched with ten controls in the background population by sex and age and the risk of hyperthyroidism was analyzed by multivariate Cox proportional-hazard models.
Results: A total of 139,521 patients with new-onset AF were included (mean age 73.5 years [SD ±12.5] and 52% males). The total number of patients initiating antithyroid medication in the 10 year period after index AF was 7,138 (5.2%), of whom 4,924 (69%) were women and 2,214 (31%) were men. The gender-stratified cumulative incidence of hyperthyroidism for new-onset AF patients and controls is shown in the Figure. Cox regression analysis showed significantly increased risk of hyperthyroidism in patients with new-onset AF compared to controls (hazard ratio [HR] 2.98; 95% confidence interval [CI] 2.84-3.12) and this effect was found for both women (HR 2.39;CI 2.26–2.53) and men (HR 5.30;CI 4.89–5.75). This risk was increased throughout the 10 year period.
Conclusions: New-onset AF is an independent long-term risk factor for later occurrence of hyperthyroidism. Increased focus on subclinical hyperthyroidism in patients with new-onset AF is warranted.
- © 2010 by American Heart Association, Inc.