Thyroid Problems Linked to Increased Risk of Dementia

Summary: Older adults who suffer from hypothyroidism are at increased risk of developing dementia. The risk is even higher in those who require thyroid hormone replacement therapy to treat their condition.

Source: AAN

Older people with hypothyroidism, also called underactive thyroid, may be at increased risk of developing dementia, according to a study published in the July 6, 2022, online issue of Neurology.

The risk of developing dementia was even higher for people whose thyroid condition required thyroid hormone replacement medication.

Hypothyroidism occurs when the thyroid gland doesn’t make enough thyroid hormones. This can slow metabolism. Symptoms include feeling tired, weight gain and sensitivity to cold.

“In some cases, thyroid disorders have been associated with dementia symptoms that can be reversible with treatment,” said study author Chien-Hsiang Weng, MD, MPH, of Brown University in Providence, Rhode Island.

“While more studies are needed to confirm these findings, people should be aware of thyroid problems as a possible risk factor for dementia and therapies that could prevent or slow irreversible cognitive decline.”

For the study, researchers looked at the health records of 7,843 people newly diagnosed with dementia in Taiwan and compared them to the same number of people who did not have dementia. Their average age was 75. Researchers looked to see who had a history of either hypothyroidism or hyperthyroidism.

Hyperthyroidism, which is also called overactive thyroid, is when the thyroid produces too much hormone. This can increase metabolism. Symptoms include unintended weight loss, rapid or irregular heartbeat and nervousness or anxiety.

A total of 102 people had hypothyroidism and 133 had hyperthyroidism.

The researchers found no link between hyperthyroidism and dementia.

Of the people with dementia, 68 people, or 0.9%, had hypothyroidism, compared to 34 of the people without dementia, or 0.4%.

This shows a brain
Hypothyroidism occurs when the thyroid gland doesn’t make enough thyroid hormones. This can slow metabolism. Symptoms include feeling tired, weight gain and sensitivity to cold. Image is in the public domain

When researchers adjusted for other factors that could affect the risk of dementia, such as sex, age, high blood pressure and diabetes, they found that people over age 65 with hypothyroidism were 80% more likely to develop dementia than people the same age who did not have thyroid problems.

For people younger than 65, having a history of hypothyroidism was not associated with an increased risk of dementia.

When researchers looked only at people who took medication for hypothyroidism, they found they were three times more likely to develop dementia than those who did not take medication. “One explanation for this could be that these people are more likely to experience greater symptoms from hypothyroidism where treatment was needed,” Weng said.

Weng noted that the observational study does not prove that hypothyroidism is a cause of dementia; it only shows an association.

A limitation of the study was that researchers were not able to include information about how severe the hypothyroidism was for participants.

About this dementia research news

Author: Natalie Conrad
Source: AAN
Contact: Natalie Conrad – AAN
Image: The image is in the public domain

Original Research: The findings will appear in Neurology

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  1. The unanswered question for me is whether these people who are being diagnosed and treated at 65 and older have had long-standing untreated subclinical/borderline hypothyroidism, cellular hypothyroidism (that wasn’t reflected in standard blood tests), or autoimmune Thyroid Peroxidase (TPO) antibodies that indicate Hashimoto’s thyroiditis.

    My theory is that people with hypothyroidism that is fully replaced — OPTIMAL thyroid function — would be at far less risk that those who go through their adulthood with borderline or suboptimal thyroid function that’s *finally* diagnosed in their 60s…

    I think we need a lot more research into this subject before anyone concludes that treating hypothyroidism in our 60s is a *cause* of dementia…

  2. I’d be interested to know what the correlation is for those who had developed hypothyroidism as a result of taking lithium carbonate as a medicine.

  3. My 70 year old sister has had hypoparathyroidism since she was 17 years old.
    Does she face an increased risk of dementia too?

  4. I want to see more about the correlation of dementia to hypothalamus and anterior pituitary. This article is way too thin on details. Surely the “cause” of the hypothyroidism was considered?

  5. Quote from article written by Chien-Hsiang Weng, MD, MPH, of Brown University in Providence, Rhode Island:

    “When researchers looked only at people who took medication for hypothyroidism, they found they were three times more likely to develop dementia than those who did not take medication. “One explanation for this could be that these people are more likely to experience greater symptoms from hypothyroidism where treatment was needed.”

    Another plausible explanation, not mentioned, is that the medication given to treat hypothyroidism is responsible for the increased incidents of dementia.

    Christina K Gross

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