biostudies-literatureDori Dthe Canadian Institutes of Health Researche70960https://www.ebi.ac.uk/biostudies/studies/S-EPMC12706624biostudies-literatureUnknown21(12)<h4>Introduction</h4>Controversial hypotheses suggest that "suboptimal" thyroid function - defined as higher-normal thyroid-stimulating hormone (TSH) (2.0 to 4.5 μIU/mL) or low-normal free thyroxine (FT4) - may increase risk of cognitive decline and dementia in older patients.<h4>Methods</h4>We examined this claim using data from the Canadian Comprehensive Assessment of Neurodegeneration and Dementia cohort (ages 50 to 91; cognitive statuses from unimpaired to dementia, rarer subtypes of dementia excluded). Thyroid function was categorized as "optimal" (TSH < 2.0 μIU/mL or FT4 ≥ 16.74 pmol/L) or "suboptimal." Six hundred eighty-eight participants had TSH data, and 476 participants had FT4 data.<h4>Results</h4>Chi-squared analyses showed no significant association between "suboptimal" thyroAlzheimer's & dementia : the journal of the Alzheimer's AssociationThyroid function and cognitive health: rethinking the relationship between "suboptimal" TSH/FT4 levels and cognitive decline.PMC12706624CNA-163902CNA-137794BDO-148341Chertkow HBorrie MSeixas-Lima BLahiri DRoncero CDori DfalseThyroid function and cognitive health: rethinking the relationship between "suboptimal" TSH/FT4 levels and cognitive decline.<h4>Introduction</h4>Controversial hypotheses suggest that "suboptimal" thyroid function - defined as higher-normal thyroid-stimulating hormone (TSH) (2.0 to 4.5 μIU/mL) or low-normal free thyroxine (FT4) - may increase risk of cognitive decline and dementia in older patients.<h4>Methods</h4>We examined this claim using data from the Canadian Comprehensive Assessment of Neurodegeneration and Dementia cohort (ages 50 to 91; cognitive statuses from unimpaired to dementia, rarer subtypes of dementia excluded). Thyroid function was categorized as "optimal" (TSH < 2.0 μIU/mL or FT4 ≥ 16.74 pmol/L) or "suboptimal." Six hundred eighty-eight participants had TSH data, and 476 participants had FT4 data.<h4>Results</h4>Chi-squared analyses showed no significant association between "suboptimal" thyro2025-01-01T00:00:00Z2025 Dec2026-06-07T05:21:34.815Z2026-06-07T03:07:12.216ZS-EPMC127066244140000710.1002/alz.70960