Associations between blood cadmium levels and cognitive function in a cross-sectional study of US adults aged 60 years or older

OBJECTIVES: The relationship between cadmium exposure and cognition has been well studied in children. However, the association between environmental cadmium exposure and cognitive function has not been researched extensively in older adults. Our goal was to evaluate the association between cognitive function and blood cadmium levels in US adults aged 60 years or older. DESIGN: A cross-sectional study. SETTING: The US National Health and Nutrition Examination Survey (NHANES). PARTICIPANTS: A total of 2068 adults aged 60 years or older who completed four cognitive assessment tests and blood cadmium detection in two waves of NHANES (2011–2014). MAIN OUTCOME MEASURES: Cognitive assessment was conducted by household interview or at a Mobile Examination Center (MEC) using the Consortium to Establish a Registry for Alzheimer’s Disease (CERAD) Word List Learning Test, the CERAD Word List Recall Test, the Animal Fluency Test and the Digit Symbol Substitution Test (DSST). We created a composite cognitive z-score to represent global cognitive function. RESULTS: The median blood cadmium concentration in the study participants was 0.35 µg/L, and the IQR was 0.24–0.56 µg/L. In linear regression analyses, adjusting for demographics, behaviour and medical history, blood cadmium as a continuous variable was inversely associated with the composite z-score (μg/L, β=−0.11, 95% CI −0.20 to −0.03). Similarly, there was a significant association between quartiles of blood cadmium and composite z-score, with somewhat lower scores in the upper quartile of exposure (blood cadmium ≥0.63 µg/L) compared with those in the lower quartile of exposure (blood cadmium <0.25 µg/L) (μg/L, β=−0.14, 95% CI −0.25 to –0.03), and there was a trend by quartiles of blood cadmium (P<0.0001). CONCLUSIONS: Our findings suggest that increased blood cadmium is associated with worse cognitive function in adults aged 60 years or older in the USA.