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Cognitive impairment linked with subclinical hypothyroidism in adults
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A relationship between subclinical hypothyroidism and cognitive impairment was found among adults younger than 75 years and those with higher thyroid-stimulating hormone concentrations, according to recent study findings published in The Journal of Clinical Endocrinology & Metabolism.
“Taking together our results, we can conclude that a possible interaction between mild thyroid deficiency and [central nervous system] function could be present in subjects younger than 75 years, while no effected was documented in the oldest (> 75 years),” the researchers wrote. “In this setting, it is worth noting that a similar figure has been described also for cardiovascular and stroke risk of [subclinical hypothyroidism] patients.”
Fabio Monzani
In the meta-analysis, Fabio Monzani, MD, of the University of Pisa in Italy, and colleagues evaluated 13 studies that met the following criteria: published data, cross-sectional, case control or longitudinal analysis enrolling at least 15 patients with subclinical hypothyroidism; well-defined normal upper limit of TSH value; and defined and unique commercial product to run TSH assay. The primary outcome of cognitive function was evaluated as composite endpoint of incidence or prevalence of dementia or difference of Mini Mental State Examination (MMSE), Wechsler Adult Intelligence Scale and Wechsler Memory Scale-Revised scores.
Among patients younger than 75 years with subclinical hypothyroidism there was a significant risk for cognitive alteration: composite endpoint (OR = 1.56; 95% CI, 1.07-2.27) and risk for dementia (OR = 1.81; 95% CI, 1.43-2.28). A positive association was found between the composite endpoint and the degree of TSH elevation (P = .005). There was no significant effect found between subclinical hypothyroidism and cognitive function: composite endpoint (OR = 1.26; 95% CI, 0.96-1.66), risk for dementia (OR = 1.42; 95% CI, 0.97-2.07) and MMSE mean difference (P = .78).
“No correlation [between subclinical hypothyroidism and cognitive function] was found while considering all the studies as a whole. The lack of utilization of age-related serum TSH reference ranges and consequent potential over-diagnosis of [subclinical hypothyroidism] in older people may account for this,” the researchers wrote. – by Amber Cox
Disclosure: The researchers report no relevant financial disclosures.
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