Activities of daily living, behavioral and psychological symptoms of dementia, and cognitive and physical function according to thyroid function in Alzheimer's disease

BackgroundThe relationships between thyroid hormone profiles and activities of daily living (ADLs), behavioral and psychological symptoms (BPSD), cognitive status, and physical function in patients with Alzheimer's disease (AD) remain poorly understood.ObjectiveThis study investigates the relationships among ADLs, BPSD, and cognitive and physical function relative to thyroid status in patients with AD.MethodsWe recruited 2484 outpatients diagnosed with AD aged 65 and older with serum free triiodothyronine (FT3), free thyroxine (FT4), and thyroid-stimulating hormone (TSH) levels measured at their first memory clinic visit. The participants were divided into five groups by their serum FT4 and TSH levels: euthyroidism, hypothyroidism, subclinical hypothyroidism, hyperthyroidism, and subclinical hyperthyroidism. Differences in dependent variables among these groups were compared using analysis of covariance. Correlations of the dependent variables with FT3, FT4, FT3/FT4, and TSH levels and the presence of non-thyroidal illness syndrome (NTIS) were examined using a multiple regression model.ResultsNo significant differences in ADLs, BPSD, and cognitive or physical performance were observed among the groups stratified by FT4 and TSH levels. Although there were slight variations according to the analytical method employed, the overall results indicated that lower FT3, higher FT4, and lower FT3/FT4 were correlated with worse ADLs, mood, and cognitive and physical function. AD patients with NTIS exhibited notably worse basic ADLs than other groups.ConclusionsThese results suggest that thyroid hormone levels are associated with ADLs, mood, and cognitive and physical function in AD patients, suggesting the need for careful monitoring of AD patients with lower FT3, higher FT4, lower FT3/FT4, and NTIS.