Associations of blood heavy metals with cognitive function in older US adults: single and mutually adjusted effects

Heavy metal exposure has been associated with various diseases. The purpose of this study was to determine the single and mutually adjusted associations between blood heavy metals and cognitive function in older adults.

This observational study utilizes data from the National Health and Nutrition Examination Survey (NHANES) between 2011 and 2014 and involved 1460 participants aged ≥ 60 years. The concentrations of blood lead (Pb), cadmium (Cd), mercury (Hg), selenium (Se), and manganese (Mn) were measured using inductively coupled plasma mass spectrometry (ICP-MS). Cognitive function was assessed using the Immediate Recall Test (IRT), delayed recall test (DRT), animal fluency test (AFT), and digit symbol substitution test (DSST). Mutually adjusted linear regression models, restricted cubic spline (RCS) analyses, and subgroup analyses were performed to evaluate individual and mutually adjusted associations between blood metal concentrations and cognitive function.

Multiple linear regression analysis revealed an inverse association between Cd concentrations and cognitive scores (β=-2.698, 95% CI: -4.842, -0.554). Blood Se levels were positive associations with cognitive scores (β = 0.049, 95% CI: 0.022, 0.076) and all four cognitive domains. The RCS showed that the dose-response association between Cd and cognitive scores appeared to be linear (P-nonlinear = 0.566), while Se exhibited a left-skewed inverted U-shaped curve with cognitive scores (P-nonlinear = 0.013).

A high concentration of Cd is strongly associated with cognitive decline. However, the protective effect of Se on cognitive function plateaus after reaching a certain concentration. These findings may have significance for the development of interventions aimed at alleviating cognitive impairment.