Abstract
BACKGROUND: Understanding the particularities of thyroid-cognition interactions in older adults is crucial in assessing the risks and evaluating therapeutic options. METHODS: Cross-sectional analyses where participants from Alzheimer's Disease Neuroimaging Initiative (ADNI) with mild cognitive impairment (MCI) and healthy controls (HC), with complete neurocognitive tests, thyroid stimulating hormone (TSH) <10 μIU/mL, and geriatric depression scale (GDS) <5, were eligible. Linear and logistic regression models, including testing for non-linearity, were performed. Sex strata were explored. RESULTS: Of the total 1845 multiethnic US-participants, with a median age of 73 (IQR: 68, 78); 887 (48 %) were females, and 1056 (57 %) had MCI. The median TSH level was 1.70 μIU/mL (IQR: 1.15, 2.40); significantly lower in MCI than HC (1.66 vs. 1.74 μIU/mL, p-value=0.02). There was a significant association between TSH and overall cognition only in males (adj. ß (Males)=-0.40[-0.74, -0.07], p-value=0.019). The odds of being diagnosed with MCI at baseline decreased with higher TSH levels in the total study population (adj. OR(Total)=0.87[0.79 0.95], p-value=0.002) and in males (adj. OR(Males)=0.80[0.70, 0.92], p-value=0.001). CONCLUSIONS: There was a sex-specific, statistically significant association between TSH levels and cognition in multiethnic middle-aged and older ADNI adults. Lower TSH levels and worse global cognition were statistically associated only in males. To precisely delineate the chronological onset of these disorders, longitudinal clinical studies are needed.