Thyroid Function Linked With Dementia Risk

By Thomas R. Collins

LAKE BUENA VISTA, Fla -- October 21, 2015 -- Thyroid function appears to play a role in the development of dementia, researchers said here at the 15th International Thyroid Congress (ITC).

Pulling details from the Rotterdam Study database on people in the Rotterdam area of the Netherlands, Layal Chaker, MD, Erasmus Medical Center, Rotterdam, the Netherlands, and colleagues analysed levels of thyroid-stimulating hormone (TSH) and dementia, along with cardiovascular and other factors.

Thyroid hormone levels could potentially affect dementia in various ways, with lower levels causing altered gene expression that can lead to Alzheimer’s disease or high levels having negative effects on the viability of neurons, also enhancing risk for dementia. In addition, both low and high levels can have adverse effects on cholinergic neurons and on vascular mechanisms, which can play a role in dementia formation.

The database included 9,466 people with information on dementia and thyroid function.

The researchers found that a higher TSH level correlated with lower risk of dementia. TSH level yielded a hazard ratio of 0.90 for dementia.

The reverse was also true: lower TSH correlated with a higher risk of dementia.

Women aged 65 years or older seemed to be the most affected, with the 10-year absolute risk of dementia falling from 15% at 0.4 mIU/L to 10% at 4.0 mIU/L. No relationship was seen in men aged 65 years or older.

Researchers also looked at thyroid function and the risk of vascular brain disease, but found no relation.

“We find high and high-normal thyroid function to be related to a higher risk of dementia,” said Dr. Chaker. “It seems to be mainly in women. And our studies on cognitive function are in line with this -- with higher TSH having a higher cognitive function. We do not really find any evidence of a vascular pathway.”

The 2015 ITC meeting is sponsored by the American Thyroid Association (ATA), the European Thyroid Association (ETA), the Latin American Thyroid Society, and the Asia & Oceania Thyroid Association.

[Presentation title: Thyroid Function and the Risk of Dementia: The Rotterdam Study. Abstract 5]
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