Hypothyroidism Correlated with Dementia Risk in Taiwanese Population 

A retrospective review of claims data from the Taiwan’s National Health Insurance Research Database (NHIRD), published in Neurology, showed a correlation between hypothyroidism and dementia in people over age 65. The odds ratio for dementia was even higher for people treated with thyroid hormone replacement medication.

Of 7,843 people diagnosed with dementia, 0.9% had hypothyroidism. These individual's records were compared with an equal number of age- and sex-matched records in the database from people without dementia diagnoses. 

After adjustment for sex, age, hypertension, and diabetes, individuals age 65 or more who had with hypothyroidism were 80% more likely (aOR, 1.81; 95% Cl 1.14-2.87; P=.011) to also have dementia. Among those who took hormone replacement therapy for hypothyroidism, the likelihood of dementia was increased by over threefold (aOR, 3.17; 95% Cl 1.04-9.69; P=.043). No correlation of hypothyroidism and dementia was seen in people under age 65.

The increased likelihood of hypothyroidism was independent of the other known risk factors, for which significant correlations were also observed, including:hypertension (P < 0.001), diabetes (P < 0.001), coronary artery disease (P<.001), depression (P<.001), tinnitus (P= .013), and alcohol dependence (P<.001).

“In some cases, thyroid disorders have been associated with dementia symptoms that can be reversible with treatment,” said Chien-Hsiang Weng, MD, MPH, clinical assistant professor, family medicine, Brown University. “One explanation for this could be that these people are more likely to experience greater symptoms from hypothyroidism where treatment was needed. 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.”

This study adds to a body of literature with contradictory results that have shown both positive and negative correlations, as well as no correlation, between dementia and hypothyroidism as measured by thyroid stimulating hormone (TSH) levels. Further studies of thyroid hormone and metabolism and dementia are needed.

These data come from health records of 7,843 people who were newly diagnosed with dementia were compared with the same number of records of people without dementia matched for age and sex and taken from the same database of health records. Mean age of all individuals whose data was reviewed was 75