title: Subclinical thyroid dysfunction and cognitive decline in old age.
abstract: BACKGROUND
  Subclinical thyroid dysfunction has been implicated as a risk factor for cognitive decline in old age, but results are inconsistent. We investigated the association between subclinical thyroid dysfunction and cognitive decline in the PROspective Study of Pravastatin in the Elderly at Risk (PROSPER).
  
  
  METHODS
  Prospective longitudinal study of men and women aged 70-82 years with pre-existing vascular disease or more than one risk factor to develop this condition (N = 5,154). Participants taking antithyroid medications, thyroid hormone supplementation and/or amiodarone were excluded. Thyroid function was measured at baseline: subclinical hyper- and hypothyroidism were defined as thyroid stimulating hormones (TSH) <0.45 mU/L or >4.50 mU/L respectively, with normal levels of free thyroxine (FT4). Cognitive performance was tested at baseline and at four subsequent time points during a mean follow-up of 3 years, using five neuropsychological performance tests.
  
  
  RESULTS
  Subclinical hyperthyroidism and hypothyroidism were found in 65 and 161 participants, respectively. We found no consistent association of subclinical hyper- or hypothyroidism with altered cognitive performance compared to euthyroid participants on the individual cognitive tests. Similarly, there was no association with rate of cognitive decline during follow-up.
  
  
  CONCLUSIONS
  We found no consistent evidence that subclinical hyper- or hypothyroidism contribute to cognitive impairment or decline in old age. Although our data are not in support of treatment of subclinical thyroid dysfunction to prevent cognitive dysfunction in later life, only large randomized controlled trials can provide definitive evidence.
authors.affiliation: Department of Gerontology and Geriatrics, Leiden University Medical Center, Leiden, The Netherlands.
authors.forename: Liselotte W
authors.initials: LW
authors.lastname: Wijsman
authors.forename: Anton J M
authors.initials: AJ
authors.lastname: de Craen
authors.forename: Stella
authors.initials: S
authors.lastname: Trompet
authors.forename: Jacobijn
authors.initials: J
authors.lastname: Gussekloo
authors.forename: David J
authors.initials: DJ
authors.lastname: Stott
authors.forename: Nicolas
authors.initials: N
authors.lastname: Rodondi
authors.forename: Paul
authors.initials: P
authors.lastname: Welsh
authors.forename: J Wouter
authors.initials: JW
authors.lastname: Jukema
authors.forename: Rudi G J
authors.initials: RG
authors.lastname: Westendorp
authors.forename: Simon P
authors.initials: SP
authors.lastname: Mooijaart
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000097:blood / Q000523:psychology*; D003072:Cognition Disorders / Q000097:blood / Q000503:physiopathology / Q000523:psychology*; D005260:Female; D006801:Humans; D006980:Hyperthyroidism / Q000097:blood / Q000503:physiopathology / Q000523:psychology*; D007037:Hypothyroidism / Q000097:blood / Q000503:physiopathology / Q000523:psychology*; D008137:Longitudinal Studies; D008297:Male; D009483:Neuropsychological Tests; D012307:Risk Factors; D013960:Thyroid Function Tests; D013961:Thyroid Gland / Q000503:physiopathology*; D013972:Thyrotropin / Q000097:blood; D013974:Thyroxine / Q000097:blood
chemical_list: D013972:Thyrotropin; D013974:Thyroxine
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