Can Hypothyroidism Increase Dementia Risk?

Dementia risk is higher in older people with hypothyroidism and even higher in those who are taking thyroid hormone replacement medication.

Highlights:

Hypothyroidism may increase dementia risk in the elderly
People on medication for hypothyroidism are three times more likely to develop dementia
However, hyperthyroidism had no link with dementia

Older people with underactive thyroid (hypothyroidism) were found to be at a higher risk of developing dementia, reveals a study published in the online issue of Neurology®, the medical journal of the American Academy of Neurology.

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

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‘Dementia risk is higher in older people with hypothyroidism and even higher in those who are taking thyroid hormone replacement medication.’

Thyroid Problems

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.

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Hyperthyroidism, 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.

Link Between Thyroid Problems and Dementia

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

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Symptoms of hypothyroidism are often general, unspecific changes in the body. Lethargy, weight gain, stiffness and cramping of muscles are some of the symptoms of hypothyroidism.

The researchers found no link between hyperthyroidism and dementia.

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

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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 could not include information about how severe hypothyroidism was for participants.

Source-Eurekalert