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Hypothyroidism not associated with mild cognitive impairment
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There is no significant correlation between hypothyroidism and mild cognitive impairment, often thought to be a precursor for Alzheimer’s, according to a recent study in JAMA Neurology.
“We did not find any significant association of [mild cognitive impairment] with clinical and subclinical hypothyroidism after accounting for possible confounding factors and interactions,” Ajay K. Parsaik, MD, of the department of psychiatry and behavior sciences at the University of Texas Medical School, and colleagues wrote. “Our findings are consistent with those of previous studies that reported a lack of association between thyroid dysfunction and cognitive decline.”
As previous studies had not looked at mild cognitive impairment (MCI) as the earliest detectable cognitive impairment, the researchers chose that as their focus in looking at 1,904 eligible patients.
MCI was present in 16.3% of individuals with normal thyroid function (n=1,450), 17.2% of those with clinical hypothyroidism (n=313) and 17.7% of those with subclinical hypothyroidism (n=141). After adjusting for age, educational level, sex, apolipoprotein E ε4, depression, diabetes, hypertension, stroke, body mass index and coronary artery disease, there was no evidence of a significant association.
The authors noted that their findings need validation in separate settings utilizing standard criteria for MCI and a longitudinal study.
Disclosure: Parsaik reports no conflicts of interest. Please see the full study for other authors’ disclosures.
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Jeffrey R. Garber, MD
This is a nicely done study that does not support screening those between ages 70 and 89 for hypothyroidism in order to identify patients with reversible mild cognitive impairment. The study also suggests that hypothyroidism, regardless of whether it is clinical or subclinical does not cause mild cognitive impairment. The latter point requires some clarification. There is little doubt that profound hypothyroidism affects cognition and may be reversible with thyroid hormone therapy. However, the incidence of untreated profound – as opposed to mild to moderate overt hypothyroidism – even in elderly populations is too low to affect the outcomes in studies such as this one or to justify screening on this basis alone.
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