NEW YORK (Reuters Health) – New research shows no association between thyroid dysfunction and cognitive decline, questioning the value of screening for subclinical thyroid dysfunction for the prevention of cognitive decline or dementia, researchers say.

“In clinical guidelines, overt and subclinical thyroid dysfunction are mentioned as causal and treatable factors for cognitive decline. However, the scientific literature on these associations shows inconsistent findings,” they note in JAMA Internal Medicine.

To investigate further, they evaluated cross-sectional and longitudinal associations between baseline thyroid dysfunction and cognitive function and dementia using individual patient data from 23 cohorts including more than 74,000 participants.

Eighty-nine percent of the participants had normal thyroid function, 0.8% had overt hyperthyroidism, 3.4% had subclinical hyperthyroidism, 5.6% had subclinical hypothyroidism and 0.9% had overt hypothyroidism.

Subclinical thyroid dysfunction was not associated with global cognitive function at baseline, annual decline in cognitive function or risk of dementia, report Dr. Nicolien van Vliet of Leiden University Medical Center, in the Netherlands, and colleagues.

“Hence, it is unlikely that treatment for otherwise undetected subclinical thyroid dysfunction would improve cognitive function,” they say.

“Moreover, the chance of over treatment is considerable, which increases the risk of atrial fibrillation, atherosclerosis, and cerebral infarction and thereby might increase the risk of cognitive decline,” they caution.

It remains uncertain whether treatment of overt hypothyroidism or hyperthyroidism is associated with cognitive decline and risk of dementia, the researchers note.

Based on their findings, they say existing clinical guidelines that recommend screening for subclinical thyroid dysfunction for prevention of cognitive decline or dementia should be revisited.

The study had no commercial funding.

SOURCE: https://bit.ly/2YqLTM0 JAMA Internal Medicine, online September 7, 2021.

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