Older people with hypothyroidism may be at increased risk of developing dementia , according to a study published in 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.
Background and objectives: Dementia has gained attention in aging societies and is estimated to affect 50 million adults worldwide in 2020, and 12% of the US population may develop a thyroid disorder in their lifetime. There have been limited studies investigating the correlation between thyroid disorder and dementia in the Asian population. Methods: Our large , nationwide population-based case-control study used the Taiwan National Health Insurance Research Database. 7,843 adults with newly diagnosed dementia without a prior history of dementia or neurodegenerative disease between 2006 and 2013 were identified and included in our study. 7,843 adults without a diagnosis of dementia before the index date were age- and gender-matched as controls. The diagnosis of hyperthyroidism or hypothyroidism was identified before the dementia diagnosis or on the same index date. Results were obtained from logistic regression models and adjusted for sex, age, history of hypertension, diabetes, coronary artery disease, depression, hyperlipidemia, alcohol dependence syndrome, tinnitus, hearing loss, and radioactive iodine treatment. Results: A total of 15,686 patients were included in the study . Both case and control groups were slightly predominantly female (4,066 [51.8%]). The mean (SD) age for those with dementia was 74.9 (11.3) years and for those without dementia was 74.5 (11.3) years. Among patients aged 65 years or older , a history of hypothyroidism was associated with a higher risk of being diagnosed with dementia (aOR, 1.81; 95% CI, 1.14-2.87; p=0.011), an association not present in patients over 50 years of age but under 65 years of age. We found that this association was most significant among patients aged 65 years or older with a history of hypothyroidism who received hypothyroidism medication (aOR, 3.17; 95% CI 1.04-9.69; p=0.043). Discussion: Our large-scale case-control study found that among people ≥ 65 years of age, those with a history of hypothyroidism were associated with an 81% increased risk of having dementia and among them, there was a more than 3-fold increase in risk of dementia with thyroid conditions requiring thyroid hormone replacement treatment. Future well-controlled prospective longitudinal studies should be conducted to elucidate these potential mechanisms and relationships. Classification of evidence: This study provides Class III evidence that among patients aged 65 years or older, a history of hypothyroidism was associated with an increased risk of being diagnosed with dementia. |
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Hypothyroidism occurs when the thyroid gland does not produce enough thyroid hormones. This can slow down the metabolism. Symptoms include feeling tired, weight gain, and sensitivity to cold.
"In some cases, thyroid disorders have been associated with dementia symptoms that may be reversible with treatment," said study author Chien-Hsiang Weng, MD, MPH, of Brown University in Providence, Rhode Island. 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 delay 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 years . The researchers looked at who had a history of hypothyroidism or hyperthyroidism . Hyperthyroidism can increase metabolism. Symptoms include unintentional weight loss, rapid or irregular heartbeats, 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 people with dementia , 68 people, or 0.9%, had hypothyroidism , compared with 34 of people without dementia , or 0.4%. When researchers adjusted for other factors that could affect dementia risk, such as sex, age, high blood pressure and diabetes, they found that people over 65 with hypothyroidism were 81% more likely to develop dementia than people of the same age who did not have thyroid problems.
For people under age 65 , having a history of hypothyroidism was not associated with an increased risk of dementia.
When researchers looked only at people taking medications for hypothyroidism, they found that they were three times more likely to develop dementia than those not taking medications. "One explanation for this could be that these people are more likely to experience greater symptoms of hypothyroidism where treatment is needed," Weng said.
Weng noted that the observational study does not prove that hypothyroidism is a cause of dementia; it just shows an association . One limitation of the study was that the researchers were unable to include information about the severity of hypothyroidism in the participants.
