title: Subclinical thyroid dysfunction and the risk of stroke: a systematic review and meta-analysis.
abstract: Subclinical thyroid dysfunction has been associated with coronary heart disease, but the risk of stroke is unclear. Our aim is to combine the evidence on the association between subclinical thyroid dysfunction and the risk of stroke in prospective cohort studies. We searched Medline (OvidSP), Embase, Web-of-Science, Pubmed Publisher, Cochrane and Google Scholar from inception to November 2013 using a cohort filter, but without language restriction or other limitations. Reference lists of articles were searched. Two independent reviewers screened articles according to pre-specified criteria and selected prospective cohort studies with baseline thyroid function measurements and assessment of stroke outcomes. Data were derived using a standardized data extraction form. Quality was assessed according to previously defined quality indicators by two independent reviewers. We pooled the outcomes using a random-effects model. Of 2,274 articles screened, six cohort studies, including 11,309 participants with 665 stroke events, met the criteria. Four of six studies provided information on subclinical hyperthyroidism including a total of 6,029 participants and five on subclinical hypothyroidism (n = 10,118). The pooled hazard ratio (HR) was 1.08 (95 % CI 0.87-1.34) for subclinical hypothyroidism (I (2) of 0 %) and 1.17 (95 % CI 0.54-2.56) for subclinical hyperthyroidism (I (2) of 67 %) compared to euthyroidism. Subgroup analyses yielded similar results. Our systematic review provides no evidence supporting an increased risk for stroke associated with subclinical thyroid dysfunction. However, the available literature is insufficient and larger datasets are needed to perform extended analyses. Also, there were insufficient events to exclude clinically significant risk from subclinical hyperthyroidism, and more data are required for subgroup analyses.
authors.affiliation: Department of Internal Medicine, Thyroid Center, Erasmus University Medical Center, Room Ee502, PO Box 2040, 3000 CA, Rotterdam, The Netherlands, l.chaker@erasmusmc.nl.
authors.forename: Layal
authors.initials: L
authors.lastname: Chaker
authors.forename: Christine
authors.initials: C
authors.lastname: Baumgartner
authors.forename: M Arfan
authors.initials: MA
authors.lastname: Ikram
authors.forename: Abbas
authors.initials: A
authors.lastname: Dehghan
authors.forename: Marco
authors.initials: M
authors.lastname: Medici
authors.forename: W Edward
authors.initials: WE
authors.lastname: Visser
authors.forename: Albert
authors.initials: A
authors.lastname: Hofman
authors.forename: Nicolas
authors.initials: N
authors.lastname: Rodondi
authors.forename: Robin P
authors.initials: RP
authors.lastname: Peeters
authors.forename: Oscar H
authors.initials: OH
authors.lastname: Franco
mesh_terms: D005260:Female; D006801:Humans; D006980:Hyperthyroidism / Q000097:blood / Q000150:complications* / Q000503:physiopathology; D007037:Hypothyroidism / Q000097:blood / Q000150:complications* / Q000503:physiopathology; D008297:Male; D020521:Stroke / Q000097:blood / Q000209:etiology*; D013960:Thyroid Function Tests; D013972:Thyrotropin / Q000097:blood
chemical_list: D013972:Thyrotropin