Thyroid function and cognition in the euthyroid elderly: a case-control study embedded in Quebec longitudinal study - NuAge.

It is presently unclear whether there is a significant association between thyroid function and cognitive decline in euthyroid elderly. This case-control study aimed to examine serum thyroid stimulating hormone (TSH), total thyroxine, free thyroxine, total triiodothyronine, and free triiodothyronine in relation to cognitive decline over a 3-year period in a subsample of 62 participants (31 pairs) aged 67 years and over at baseline from the NuAge study (Quebec longitudinal study). They were matched for age, sex and global cognition. In conditional regression logistic models, there was no significant association between any thyroid function indices and the 3-year risk of cognitive decline as measured with the Modified Mini-Mental State Examination (3MS). TSH and thyroid hormones do not appear to be associated with cognitive decline in euthyroid older persons. These findings need confirmation given the small number of pairs of subjects.
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