Thyroid stimulating hormone, cognitive impairment and depression in an older korean population

Associations of thyroid dysfunction with cognitive impairment and depression in late-life have been described but remain controversial. This study aimed to investigate the associations of serum thyroid stimulating hormone (TSH) levels with cognitive impairment and depression after controlling for potential confounding factors.

The sample consisted of 495 community residents aged 65 or over in whom serum TSH had been assayed. Cognitive impairment was defined using the Community Screening Interview for Dementia, and depression was diagnosed using the Geriatric Mental State schedule. Age, gender, education, smoking history, physical activity, blood pressure, diabetes, and serum total cholesterol and albumin were included as covariates.

There was a significant association between lower (hyperthyroid) serum TSH levels (<0.5 mIU/L) and cognitive impairment after adjustment [odds ratio 7.12 (95% confidence interval 1.35-37.5)]. However, no association was found between TSH levels and depression.

Based on TSH levels, hyperthyroidism but not hypothyroidism was associated with cognitive impairment in this sample, and we found no evidence for an association of either with depression.