Low micronutrients worsen effects of blood heavy metals on cognitive function

Blood concentrations of heavy metals tend to induce cognitive decline, especially among individuals with lower micronutrient status, reveals a study.

A group of researchers analysed data from 2,858 participants aged ≥60 years in the National Health and Nutrition Examination Survey 2011‒2014. They used multivariable linear and logistic regression models to examine the main effects of heavy metals and micronutrients and their additive and multiplicative interactions on cognitive function.

After adjustment for confounders, blood concentrations of lead (β, ‒1.67, 95 percent confidence interval [CI], ‒3.32 to ‒0.03) and cadmium (β, ‒2.02, 95 percent CI, ‒3.19 to ‒0.85) showed an inverse association with the Digit Symbol Substitution Test (DSST) score (a higher score indicating better cognitive function), while serum 25-hydroxyvitamin D (25[OH]D; β, 2.23, 95 percent CI, 0.88‒3.59) demonstrated a positive association.

Furthermore, significant additive and multiplicative interactions were observed between blood lead and erythrocyte folate, between blood lead and serum 25(OH)D, and between blood cadmium and erythrocyte folate and low DSST score.

Individuals in quartiles (Q) 2 through 4 showed a progressively higher risk of low cognitive functions assessed by the DSST score (Q2: odds ratio [OR], 1.58, 95 percent CI, 0.95‒2.61; Q3: OR, 2.00, 95 percent CI, 1.18‒3.39; Q4: OR, 2.45, 95 percent CI, 1.44‒4.17; p_trend=0.00083) than those in the first quartile of a weighted composite score of risk factors (defined as greater than or equal to the median for two metals or less than the median for three micronutrients).

“This study revealed that the neurodegenerative influence of heavy metals is more pronounced in individuals with lower micronutrient status,” the researchers said. “If the results of the present study are confirmed by future studies, reducing heavy metal exposure and improving micronutrient status may offer a novel and practical strategy for preventing cognitive decline and dementia.”