title: Free thyroxine index and risk of stroke: results from the National Health and Nutrition Examination Survey Follow-up Study.
abstract: BACKGROUND
  The long-term risks of stroke associated with hypothyroidism and hyperthyroidism is unknown. We evaluated the long-term risk of stroke with hypothyroidism and hyperthyroidism compared with euthyroid status.
  
  
  METHODS
  We used the 20-year follow-up data for adults aged 25 to 74 years who participated in the First National Health and Nutrition Examination Survey Follow-up Study. Hypothyroidism or hyperthyroidism was diagnosed by free thyroxine index measurements at baseline evaluation and incident events were determined from hospital records and death certificates during follow-up. Relative risk (RR) of stroke, ischemic stroke, and intracerebral hemorrhage for each category of thyroid function were determined by Cox proportional hazards analysis after adjustment for potential confounding variables.
  
  
  RESULTS
  A total of 5,269 participants (mean age 48+/-14 years; 2,379 men) were evaluated. Hypothyroidism and hyperthyroidism were diagnosed in 493 (9.4%) and 34 (0.7%) participants, respectively. After adjustment for covariates, a significantly higher RR for all strokes and for ischemic stroke was observed in participants with hypothyroidism (RR 1.6; 95% confidence interval (CI), 1.0-2.6 and RR 1.6, 95% CI, 1.0-2.7, respectively). Hyperthyroidism was not associated with an increased risk for stroke.
  
  
  CONCLUSIONS
  An increased risk for stroke (particularly ischemic stroke) was observed in patients with hypothyroidism.
authors.affiliation: Epidemiological and Outcomes Research Division, Zeenat Qureshi Stroke Research Center, Department of Neurology and Neurosciences, University of Medicine and Dentistry of New Jersey, Newark, NJ, USA. aiqureshi@hotmail.com
authors.forename: Adnan I
authors.initials: AI
authors.lastname: Qureshi
authors.forename: Fareed K
authors.initials: FK
authors.lastname: Suri
authors.forename: Abu
authors.initials: A
authors.lastname: Nasar
authors.forename: Jawad F
authors.initials: JF
authors.lastname: Kirmani
authors.forename: Afshin A
authors.initials: AA
authors.lastname: Divani
authors.forename: Wayne H
authors.initials: WH
authors.lastname: Giles
mesh_terms: D000328:Adult; D000368:Aged; D003625:Data Collection; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D006980:Hyperthyroidism / Q000097:blood / Q000150:complications; D007037:Hypothyroidism / Q000097:blood / Q000150:complications; D008297:Male; D008875:Middle Aged; D016016:Proportional Hazards Models; D012307:Risk Factors; D020521:Stroke / Q000097:blood* / Q000453:epidemiology / Q000209:etiology*; D013974:Thyroxine / Q000097:blood*; D014481:United States / Q000453:epidemiology
chemical_list: D013974:Thyroxine