title: New-onset atrial fibrillation is a predictor of subsequent hyperthyroidism: a nationwide cohort study.
abstract: OBJECTIVE
  To examine the long-term risk of hyperthyroidism in patients admitted to hospital with new-onset AF. Hyperthyroidism is a well-known risk factor for atrial fibrillation (AF), but it is unknown whether new-onset AF predicts later-occurring hyperthyroidism.
  
  
  RESULTS
  All patients admitted with new-onset AF in Denmark from 1997-2009, and their present and subsequent use of anti-thyroid medication was identified by individual-level linkage of nationwide registries. Patients with previous thyroid diagnosis or thyroid medication use were excluded. Development of hyperthyroidism was assessed as initiation of methimazole or propylthiouracil up to a 13-year period. Risk of hyperthyroidism was analysed by Poisson regression models adjusted for important confounders such as amiodarone treatment. Non-AF individuals from the general population served as reference. A total of 145,623 patients with new-onset AF were included (mean age 66.4 years [SD ±13.2] and 55.3% males) of whom 3% (4,620 events; 62.2% women) developed hyperthyroidism in the post-hospitalization period compared to 1% (48,609 events; 82% women) in the general population (n = 3,866,889). In both women and men we found a significantly increased risk of hyperthyroidism associated with new-onset AF compared to individuals in the general population. The highest risk was found in middle-aged men and was consistently increased throughout the 13-year period of observation. The results were confirmed in a substudy analysis of 527,352 patients who had thyroid screening done.
  
  
  CONCLUSIONS
  New-onset AF seems to be a predictor of hyperthyroidism. Increased focus on subsequent risk of hyperthyroidism in patients with new-onset AF is warranted.
authors.affiliation: Department of Cardiology, Gentofte University Hospital, Hellerup, Denmark. cselmer@gmail.com
authors.forename: Christian
authors.initials: C
authors.lastname: Selmer
authors.forename: Morten Lock
authors.initials: ML
authors.lastname: Hansen
authors.forename: Jonas Bjerring
authors.initials: JB
authors.lastname: Olesen
authors.forename: Charlotte
authors.initials: C
authors.lastname: Mérie
authors.forename: Jesper
authors.initials: J
authors.lastname: Lindhardsen
authors.forename: Anne-Marie Schjerning
authors.initials: AM
authors.lastname: Olsen
authors.forename: Jesper Clausager
authors.initials: JC
authors.lastname: Madsen
authors.forename: Ulla
authors.initials: U
authors.lastname: Schmidt
authors.forename: Jens
authors.initials: J
authors.lastname: Faber
authors.forename: Peter Riis
authors.initials: PR
authors.lastname: Hansen
authors.forename: Ole Dyg
authors.initials: OD
authors.lastname: Pedersen
authors.forename: Christian
authors.initials: C
authors.lastname: Torp-Pedersen
authors.forename: Gunnar Hilmar
authors.initials: GH
authors.lastname: Gislason
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001281:Atrial Fibrillation / Q000150:complications*; D015331:Cohort Studies; D003718:Denmark / Q000453:epidemiology; D011307:Drug Prescriptions / Q000706:statistics & numerical data; D005260:Female; D006760:Hospitalization / Q000706:statistics & numerical data; D006801:Humans; D006980:Hyperthyroidism / Q000150:complications* / Q000175:diagnosis / Q000188:drug therapy / Q000453:epidemiology*; D008297:Male; D008875:Middle Aged; D012306:Risk; D055815:Young Adult