Associations Between Serum Selenium, Zinc, and Copper Levels and Cognitive Function in the Elderly

Background/Objectives: Cognitive decline in older people is greatly affected by various risk factors, especially imbalances in trace elements. This study aimed to examine the relationships between serum levels of selenium, zinc, and copper and cognitive impairment. This study included 854 participants aged 63 to 85 years. Methods: We conducted clinical assessments of metabolic disorders and measured serum levels of selenium, zinc, and copper. Cognitive impairment was evaluated using the Mini-Cog test. Results: The primary analysis identified significant differences (all p < 0.05) in age, body mass index, waist circumference, various metabolic parameters (such as fasting plasma glucose, glycated hemoglobin, and plasma triglyceride levels) and some cardiometabolic indices between the groups with and without cognitive impairment. Further assessments using multiple logistic regression and receiver operating characteristic analysis showed an association between increased serum selenium and zinc levels and a protective effect against cognitive impairment. In contrast, elevated serum copper levels were identified as a risk factor for cognitive impairment. This analysis also demonstrated high sensitivity and specificity, along with established cut-off levels for all of the trace elements studied. Conclusions: The Mini-Cog test is an effective cognitive screening test for the older population. Our findings establish a significant association between the balanced status of key antioxidant trace elements and cognitive health. Specifically, adequate serum selenium and zinc levels are associated with enhanced cognitive performance, while elevated copper may indicate a pro-oxidant state detrimental to cognitive function. Consequently, these three elements offer promise as practical, accessible biomarkers for the early identification and risk stratification of individuals susceptible to cognitive impairment. Future research should prioritize clinical trials focused on targeted nutritional strategies—specifically optimizing dietary intake and/or supplementation of selenium and zinc while carefully managing copper balance—as a viable primary prevention approach to reduce the global burden of cognitive decline.