Thyrotoxicosis linked to increased risk for cognitive disorder in older adults

Key takeaways:

• Those exposed to thyrotoxicosis had a cognitive disorder incidence of 11% by age 75 years.
• All-cause thyrotoxicosis was linked to a 39% increased risk for cognitive disorder across all ages.

Exposure to either endogenous or exogenous thyrotoxicosis was associated with a higher risk for cognitive disorder in older adults, a study in JAMA Network Open found.

According to the American Thyroid Association, the proportion of the U.S. population taking thyroid hormone has risen significantly in the last couple decades, increasing from 4.1% in 1997 to 8% in 2016.

However, there is concern of unintended consequences from overtreatment in older adults, Jennifer S. Mammen, MD, PhD, MPhil, an assistant professor of medicine at Johns Hopkin University, told Healio.

“One still controversial possible consequence is dementia — there are several cohort studies showing an association with thyroid disease and cognition, but these mostly exclude overtreatment as a cause, and a large meta-analysis found that the effect was present but not statistically significant, probably because the numbers with natural disease are so small,” she said.

The researchers aimed to better understand the relationship between thyrotoxicosis and the incidence of dementia by analyzing electronic health records of 65,931 patients aged 65 years and older who were receiving primary care from Jan. 1, 2014, to May 6, 2023.

They found that patients exposed to thyrotoxicosis during this study period had a cognitive disorder incidence of 11% (95% CI, 8.4%-14.2%) at age 75 years, compared with 6.4% (95% CI, 6%-6.8%) for those who were not exposed.

At age 85 years, cognitive disorder incidence was 34% (95% CI, 29.2%-39.9%) for those exposed and 25.9% (95% CI, 25%-26.8%) for those not exposed.

After Mammen and colleagues adjusted for possible cofounders, all-cause thyrotoxicosis was significantly associated with the risk for a cognitive disorder diagnosis (adjusted HR = 1.39; 95% CI, 1.18-1.64) across age groups.

Additionally, exogenous thyrotoxicosis remained a significant risk factor (adjusted HR = 1.34; 95% CI, 1.1-1.63) when stratified for cause and severity and was suggestive of a dose response.

Mammen said two findings particularly stood out to her, the first being “that we see a dose response — the risk is higher for people with more severe thyrotoxicosis.”

“Secondly, we see a similar effect with two different types of exposure — both thyroid disease and excess thyroid hormone treatment,” she said.

Mammen explained that “it is important to realize that thyroid hormone therapy has a therapeutic range that needs to be respected.”

“Importantly, for older adults, dose requirements often decrease with aging, and that means that treatment needs to be monitored and doses adjusted appropriately,” she said. “We already knew that excess thyroid hormone increases the risk for atrial fibrillation and there [are] also data that there is an increased risk of osteoporotic fracture, so now we have yet another aging-related morbidity that is potentially accelerated by thyrotoxicosis.”

References:

• Adams R, et al. JAMA Intern Med. 2023;doi:10.1001/jamainternmed.2023.5619.
• Hypothyroidism. https://www.thyroid.org/patient-thyroid-information/ct-for-patients/october-2020/vol-13-issue-10-p-8-9/. Accessed Oct. 25, 2023.