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 ...