Blood Lead, Blood Manganese, and Memory in Older US Adults

Abstract

Background: Lead and manganese are neurotoxicants; however, it is unclear whether co-exposure to these metals results in a synergistic neurotoxicity. Aims: Assess the relationship between blood lead (BPb) and/or blood manganese (BMn) with memory. Methods: This was a cross-sectional analysis of 1463 elderly (=60 years) individuals from the National Health and Nutrition Examination Survey (NHANES) 2011-2012; this is the only period BMn is available. Blood samples were analyzed for BPb and BMn using ICP-MS. Blood metals were natural-log transformed for analyses. Self-reported memory problems in the past week were dichotomized. Analysis included appropriate survey weights and linearized standard errors. Multivariable logistic regression models examined the relationship between Pb, Mn, or both with memory. Models were adjusted for age, sex, race/ethnicity, education, smoking (based on cotinine) and self- reported health status. Models were also stratified by sex and elevated PbB or BMn. Results: Geometric mean BPb and BMn were 1.60 µg/dL (95% confidence interval (CI): 1.55, 1.65) and 8.64 µg/L (8.48, 8.80), respectively. The adjusted odds ratio (aOR) of memory with a one-unit increase of ln(BPb) was 1.03 (0.76, 1.39) among all elderly and 1.45 (1.00, 2.11) among males only. There was a borderline significant (p=0.09) association of MnB with memory. The aOR for BMn and memory was higher among those in the highest quartile of BPb; however, neither this association, nor a model including an interaction term for BMn-BPb, was statistically significant. Conclusion: Our results demonstrated a sex-specific association of BPb with self- reported memory. Although not statistically significant, our results also suggest the potential for an association of BMn with memory, with a greater impact among those with high Pb exposure. Inclusion of neurocognitive test outcome results and longer- term exposure assessments for metals are recommended for future research.