title: Hypothyroidism and risk of mild cognitive impairment in elderly persons: a population-based study.
abstract: OBJECTIVE
  An association of clinical and subclinical hypothyroidism with mild cognitive impairment (MCI) has not been established.
  
  
  OBJECTIVE
  To evaluate the association of clinical and subclinical hypothyroidism with MCI in a large population-based cohort.
  
  
  METHODS
  A cross-sectional, population-based study was conducted in Olmsted County, Minnesota. Randomly selected participants were aged 70 to 89 years on October 1, 2004, and were without documented prevalent dementia [CORRECTED]. A total of 2050 participants were evaluated and underwent in-person interview, neurologic evaluation, and neuropsychological testing to assess performance in memory, attention/executive function, and visuospatial and language domains. Participants were categorized by consensus as being cognitively normal, having MCI, or having dementia according to published criteria. Clinical and subclinical hypothyroidism were ascertained from a medical records linkage system.
  
  
  METHODS
  Association of clinical and subclinical hypothyroidism with MCI.
  
  
  RESULTS
  Among 1904 eligible participants, the frequency of MCI was 16% in 1450 individuals with normal thyroid function, 17% in 313 persons with clinical hypothyroidism, and 18% in 141 individuals with subclinical hypothyroidism. After adjusting for covariates (age, educational level, sex, apolipoprotein E ε4, depression, diabetes mellitus, hypertension, stroke, body mass index, and coronary artery disease) we found no significant association between clinical or subclinical hypothyroidism and MCI (odds ratio [OR], 0.99 [95% CI, 0.66-1.48] and 0.88 [0.38-2.03], respectively). No effect of sex interaction was seen on these effects. In stratified analysis, the odds of MCI with clinical and subclinical hypothyroidism among men was 1.02 (95% CI, 0.57-1.82) and 1.29 (0.68-2.44) and, among women, was 1.04 (0.66-1.66) and 0.86 (0.37-2.02), respectively.
  
  
  CONCLUSIONS
  In this population-based cohort of elderly people, neither clinical nor subclinical hypothyroidism was associated with MCI. Our findings need to be validated in a separate setting using the published criteria for MCI and confirmed in a longitudinal study.
authors.affiliation: Department of Psychiatry and Behavior Sciences, The University of Texas Medical School, Houston2Mayo Alzheimer's Disease Research Center, Mayo Clinic, Rochester, Minnesota3Department of Neurology, Mayo Clinic, Rochester, Minnesota.
authors.forename: Ajay K
authors.initials: AK
authors.lastname: Parsaik
authors.affiliation: Mayo Alzheimer's Disease Research Center, Mayo Clinic, Rochester, Minnesota3Department of Neurology, Mayo Clinic, Rochester, Minnesota4Department of Clinical Neuroscience, School of Medicine and Health Sciences, University of North Dakota, Fargo.
authors.forename: Balwinder
authors.initials: B
authors.lastname: Singh
authors.affiliation: Department of Neurology, Mayo Clinic, Rochester, Minnesota5Division of Epidemiology, Department of Health Sciences Research, Mayo Clinic, Rochester, Minnesota.
authors.forename: Rosebud O
authors.initials: RO
authors.lastname: Roberts
authors.affiliation: Division of Biomedical Statistics and Informatics, Department of Health Sciences Research, Mayo Clinic, Rochester, Minnesota.
authors.forename: Shane
authors.initials: S
authors.lastname: Pankratz
authors.affiliation: Division of Biomedical Statistics and Informatics, Department of Health Sciences Research, Mayo Clinic, Rochester, Minnesota.
authors.forename: Kelly K
authors.initials: KK
authors.lastname: Edwards
authors.affiliation: Department of Psychiatry and Psychology, Mayo Clinic, Scottsdale, Arizona8Department of Neurology, Mayo Clinic, Scottsdale, Arizona.
authors.forename: Yonas E
authors.initials: YE
authors.lastname: Geda
authors.affiliation: Division of Endocrinology, Department of Internal Medicine, Mayo Clinic, Rochester, Minnesota.
authors.forename: Hossein
authors.initials: H
authors.lastname: Gharib
authors.affiliation: Mayo Alzheimer's Disease Research Center, Mayo Clinic, Rochester, Minnesota3Department of Neurology, Mayo Clinic, Rochester, Minnesota.
authors.forename: Bradley F
authors.initials: BF
authors.lastname: Boeve
authors.affiliation: Mayo Alzheimer's Disease Research Center, Mayo Clinic, Rochester, Minnesota3Department of Neurology, Mayo Clinic, Rochester, Minnesota.
authors.forename: David S
authors.initials: DS
authors.lastname: Knopman
authors.affiliation: Mayo Alzheimer's Disease Research Center, Mayo Clinic, Rochester, Minnesota3Department of Neurology, Mayo Clinic, Rochester, Minnesota.
authors.forename: Ronald C
authors.initials: RC
authors.lastname: Petersen
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D060825:Cognitive Dysfunction / Q000175:diagnosis* / Q000453:epidemiology* / Q000523:psychology; D015331:Cohort Studies; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D007037:Hypothyroidism / Q000175:diagnosis* / Q000453:epidemiology* / Q000523:psychology; D008297:Male; D011159:Population Surveillance / Q000379:methods*; D012042:Registries; D012307:Risk Factors