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Association Between Thyroid Dysfunction and Incident Dementia in the Atherosclerosis Risk in Communities Neurocognitive Study.

TitleAssociation Between Thyroid Dysfunction and Incident Dementia in the Atherosclerosis Risk in Communities Neurocognitive Study.
Publication TypeJournal Article
Year of Publication2019
AuthorsGeorge KM, Lutsey PL, Selvin E, Palta P, Windham BGwen
Secondary AuthorsFolsom AR
JournalJ Endocrinol Metab
Volume9
Issue4
Pagination82-89
Date Published2019 Aug
ISSN1923-2861
Abstract

Background: Abnormal thyroid hormone levels (high or low) and autoimmunity from autoimmune thyroid disease (AITD) may increase dementia risk.

Methods: We examined the associations of thyroid dysfunction or possible AITD in 1990 - 1992 with dementia through 2017 in the Atherosclerosis Risk in Communities (ARIC) Neurocognitive Study. Thyroid dysfunction (subclinical and overt hypo- or hyperthyroidism and euthyroidism) was categorized from serum thyroid-stimulating hormone (TSH) and free thyroxine (FT4) cut-points and AITD from anti-thyroid peroxidase (anti-TPO) antibody positivity. Dementia was identified primarily based on cognitive test performance, neuropsychological examinations and clinician review of suspected cases. Additional cases of dementia were ascertained through telephone interviews or relevant hospital and death certificate codes. Cox regression with multivariable adjustment was used for analysis.

Results: After exclusions for missing data, 12,481 participants were included in the analysis (mean index exam age 57 ┬▒ 5.7 (44% male, 25% black)), and 2,235 incident dementia cases were identified. AITD was not significantly associated with dementia. Subclinical hypothyroidism was associated with a lower risk of dementia (hazard ratio (HR) (95% confidence interval (CI)): 0.74 (0.60 - 0.92)), while overt hyperthyroidism was associated with a higher risk of dementia (HR (95% CI): 1.40 (1.02 - 1.92)) compared to euthyroid participants. Participants with serum FT4 concentrations above the 95th percentile were at an increased risk of dementia compared to those in the middle 90% of FT4 (HR (95% CI): 1.23 (1.02 - 1.48)).

Conclusions: Subclinical hypothyroidism was associated with reduced risk of dementia, whereas overt hyperthyroidism, particularly very elevated FT4, was associated with increased risk of dementia. The association between subclinical hypothyroidism and reduced risk of dementia cannot be explained, but may have been an artifact due to change. By extrapolation, effective treatment of overt hyperthyroidism may modestly reduce dementia risk in older adults.

DOI10.14740/jem588
Alternate JournalJ Endocrinol Metab
PubMed ID32411312
PubMed Central IDPMC7223793
Grant ListK24 DK106414 / DK / NIDDK NIH HHS / United States
R01 DK089174 / DK / NIDDK NIH HHS / United States
R01 HL059367 / HL / NHLBI NIH HHS / United States
T32 HL007779 / HL / NHLBI NIH HHS / United States