Association between mixture exposure to metals in urine and cognitive function in older adults in the United States: NHANES 2011-2014.

AIMS

The effects of exposure to individual metals on cognitive function have been widely reported, but research on the effects of metal mixtures is rare. This study aims to investigate the association of exposure to both individual metals and multiple metals in urine on cognitive function in US elderly.

METHODS

Data derived from the National Health and Nutrition Examination Survey 2011-2014 were utilized in this cross-sectional study. A total of 13 urinary metals were determined using inductively coupled plasma mass spectrometry. Cognitive function assessments included the Consortium to Establish a Registry for Alzheimer's Disease (CERAD) word learning test, the CERAD word recall test, the animal fluency test, and the Digit Symbol Substitution test (DSST). To assess the relationships between multiple metal exposures and cognitive performance, linear regression and Bayesian kernel machine regression (BKMR) and the weighted quantile sum (WQS) regression models were employed.

RESULTS

A total of 1018 older adults were included. The participants' mean scores on the CERAD word learning test, the CERAD word recall test, the animal fluency test, and the DSST were 19.04 ± 4.62, 5.96 ± 2.30, 16.71 ± 5.57 and 45.56 ± 17.07, respectively. There were 10 metals with detection rates higher than 80 %. The linear regression model revealed that higher levels of barium (Ba), cadmium (Cd), lead (Pb), and tungsten (W) were associated with a decline in cognitive function scores. Conversely, increased levels of molybdenum (Mo), cobalt (Co), strontium (Sr), and thallium (Tl) were associated with improved cognitive function scores. Furthermore, BKMR model demonstrated that the slope of the dose-response curve between Mo and animal fluency test score decreased with increasing concentrations of Cd, suggesting an interaction effect of Mo and Cd exposure on cognitive function. WQS regression model demonstrated a significant negative association between exposure to metal mixtures and DSST score (β=-2.42, p < 0.001).

CONCLUSIONS

Our study suggests significant associations between several metals, such as Ba, Cd, Pb, W, Mo, Co, Sr and Tl, and cognitive function in older adults. Moreover, there is an interaction between Mo and Cd on cognitive function under metal co-exposure conditions. Prospective studies are needed to confirm the potential causal relationship.