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Dementia risk elevated in subclinical hyperthyroidism with suppressed TSH
Adults with subclinical hyperthyroidism and suppressed thyroid-stimulating hormone had an increased risk for dementia and a larger decline in cognitive score compared with euthyroid adults, while those with subclinical hyperthyroidism with mildly decreased thyroid-stimulating hormone or subclinical hypothyroidism had not, study data show.
Carole E. Aubert, MD, of the department of general internal medicine at Bern University Hospital and the University of Bern in Switzerland, and colleagues evaluated data from the Health, Aging and Body Composition (Health ABC) Study on 2,558 adults (mean age, 75.1 years; 51.8% women) to determine whether subclinical thyroid dysfunction is associated with dementia and cognitive decline.
Researchers assessed participants’ cognition using the Modified Mini-Mental State examination at the baseline visit of Health ABC and at least one follow-up visit. Median follow-up was 9 years.
Eighty-five percent of participants were euthyroid, 0.9% had subclinical hyperthyroidism with suppressed TSH (TSH, < 0.1 mIU/L with normal free thyroxine [T4]), 2.3% had subclinical hyperthyroidism with mildly decreased TSH (TSH, 0.1-0.44 mIU/L), 12.3% had subclinical hypothyroidism (TSH, 4.5-19.99 mIU/L with normal free T4) and 9.9% were on thyroxine medication at baseline.
Through follow-up, 22.4% of participants developed dementia: 85.9% with euthyroidism, 1.2% with subclinical hyperthyroidism and suppressed TSH, 2.3% with subclinical hyperthyroidism and mildly decreased TSH, and 10.6% with subclinical hypothyroidism.
Participants with subclinical hyperthyroidism and suppressed TSH had an increased risk for dementia (adjusted HR = 2.38; 95% CI, 1.13-5.04) compared with participants with euthyroidism; the risk remained increased after adjustment for cardiovascular risk factors (adjusted HR = 2.41; 95% CI, 1.14-5.1). The risk for dementia was not increased in subclinical hyperthyroidism and mildly decreased TSH or in subclinical hypothyroidism.
The risk for dementia was also increased in participants with subclinical hyperthyroidism and suppressed THS who used thyroxine medication at baseline (HR = 1.66; 0.5-5.53) compared with euthyroid participants, with similar results after adjustment for CV risk factors (HR = 1.98; 95% CI, 0.58-6.75).
Compared with participants with euthyroidism, participants with subclinical hyperthyroidism and suppressed TSH had a larger decline in the Modified Mini-Mental State score (adjusted mean change, –3.89).
“We prospectively found that subclinical hyperthyroidism with suppressed TSH is associated with an increased risk of dementia and a larger cognitive decline in an elderly population,” Aubert told Endocrine Today. “Further prospective studies with a larger sample size or an individual participant data analysis with information on different types of dementia with a larger number of participants with subclinical hyperthyroidism are warranted to confirm our results and ascertain more specific associations. If our results are confirmed a randomized, controlled trial would be needed to assess if treating subclinical hyperthyroidism may reduce the risk of dementia.” – by Amber Cox
For more information:
Carole E. Aubert, MD, can be reached at caroleelodie.aubert@insel.ch.
Disclosures: The authors report no relevant financial disclosures.