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The association between subclinical thyroid dysfunction and dementia: The Health, Aging and Body Composition (Health ABC ) Study
Author(s) -
Aubert Carole E.,
Bauer Douglas C.,
da Costa Bruno R.,
Feller Martin,
Rieben Carole,
Simonsick Eleanor M.,
Yaffe Kristine,
Rodondi Nicolas
Publication year - 2017
Publication title -
clinical endocrinology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.055
H-Index - 147
eISSN - 1365-2265
pISSN - 0300-0664
DOI - 10.1111/cen.13458
Subject(s) - subclinical infection , dementia , medicine , euthyroid , prospective cohort study , thyroid function , population , endocrinology , cohort , cohort study , thyroid , disease , environmental health
Summary Objective Data on the association between subclinical thyroid dysfunction and dementia are limited and conflicting. We aimed to determine whether subclinical thyroid dysfunction was associated with dementia and cognitive decline. Design Population‐based prospective cohort study. Patients Adults aged 70‐79 years with measured thyroid function, but no dementia at baseline, and Modified Mini‐Mental State (3 MS ) at baseline and follow‐up. Measurements Primary outcome was incident‐adjudicated dementia, based on 3 MS , hospital records and dementia drugs. Secondary outcome was change in 3 MS . Models were adjusted for age, sex, race, education and baseline 3 MS , and then further for cardiovascular risk factors. Results Among 2558 adults, 85% were euthyroid ( TSH 0.45‐4.49m IU /L), 2% had subclinical hyperthyroidism with mildly decreased TSH ( TSH 0.10‐0.44 m IU /L), 1% subclinical hyperthyroidism with suppressed TSH ( TSH < 0.10 m IU /L with normal free thyroxine [ FT 4]) and 12% subclinical hypothyroidism ( TSH 4.50‐19.99 m IU /L with normal FT 4). Over 9 years, 22% developed dementia. Compared to euthyroidism, risk of dementia was higher in participants with subclinical hyperthyroidism with suppressed TSH ( HR 2.38, 95% CI = 1.13;5.04), while we found no significant association in those with mildly decreased TSH ( HR 0.79, 95% CI = 0.45;1.38) or with subclinical hypothyroidism ( HR 0.91, 95% CI = 0.70;1.19). Participants with subclinical hyperthyroidism with suppressed TSH had a larger decline in 3 MS (−3.89, 95% CI = −7.62; −0.15). Conclusions Among older adults, subclinical hyperthyroidism with a TSH < 0.10 m IU /L was associated with a higher risk of dementia and a larger cognitive decline, while subclinical hyperthyroidism with mildly decreased TSH or subclinical hypothyroidism were not.