Low thyroid-stimulating hormone levels linked with cognitive impairment
Thyrotoxicosis from any cause, including medical treatment, was associated with an increased risk of being diagnosed with a cognitive disorder among those ages 65 years and older, a new analysis found.
Elevated thyroid hormone levels are associated with an increased risk of mild cognitive impairment or dementia among patients ages 65 years and older, new research shows.
Data were gleaned from electronic health records of patients receiving primary care at Johns Hopkins Community Physicians Network between 2014 and 2023. Fifty-six percent of participants were female, and 69.9% were White. None of the patients had a history of low thyrotropin (TSH) levels or a diagnosis of a cognitive disorder in the six months preceding their first visit. Median patient age at first visit was 68 years. Results of the cohort study were published by JAMA Internal Medicine on Oct. 23.
Of the 65,931 patients included in the analysis, there were 24,867 measurements of low TSH (based on assay-specific reference ranges) found in 2,710 patients, which the study defined as thyrotoxicosis. By age 75 years, 11% (95% CI, 8.4% to 14.2%) of patients exposed to thyrotoxicosis had a cognitive disorder (defined as mild cognitive impairment or dementia) , compared with 6.4% (95% CI, 6.0% to 6.8%) of individuals not exposed to thyrotoxicosis. These totals rose to 34% and 25%, respectively, at age 85 years. Adjusted analyses showed all-cause thyrotoxicosis was linked with a cognitive disorder diagnosis across age groups (adjusted hazard ratio [HR], 1.39 [95% CI, 1.18 to 1.64]; P<0.001).
Most low TSH levels resulted from exogenous causes (overtreatment with thyroid hormone), and sex stratification “revealed a strong female predominance for iatrogenic overtreatment,” the study authors wrote. After stratification for cause and severity, data showed exogenous thyrotoxicosis was a significant risk factor for a cognitive disorder diagnosis (adjusted HR, 1.34 [95% CI, 1.10 to 1.63]; P=0.003). In addition, more severe thyrotoxicosis was linked with a higher risk of incident cognitive disorder.
The results highlight the importance of understanding the negative effects of thyroid hormone overtreatment to help guide prescribing practice, the study authors said.
An accompanying editorial said that the current study “addresses a potential modifiable risk factor that may be associated with cognitive impairment and/or dementia in older adults.” Thyroid hormone overtreatment is also associated with a heightened risk of cardiovascular events, which may play a role in the elevated risk of cognitive decline, the editorialists noted. “Future guidelines must critically reevaluate the existing evidence and provide judicious recommendations regarding thyroid hormone management in older adults, considering its association with comorbidities and cognition,” they wrote.