Multiple metal exposures and metabolic syndrome: A cross-sectional analysis of the National Health and Nutrition Examination Survey 2011-2014

Background: Epidemiologic studies suggest toxic metals are linked with diabetes and cardiovascular disease, while experimental studies indicate nutritionally essential metals are involved in the metabolism of macro nutrients and defense against oxidative stress. Objectives: We sought to evaluate how essential and toxic metals are cross-sectionally related to metabolic syndrome, a clustering of cardiometabolic conditions. Methods: Using data from the 2011-2014 National Health and Nutrition Examination Survey (n = 1088), we characterized metal concentrations as measured in spot urine (arsenic, cadmium, and inorganic/elemental mercury), whole blood (manganese, lead, methylmercury, and selenium), and serum (copper and zinc) samples. Principal component analysis was performed to derive patterns of exposures. Metabolic syndrome was defined according to the 2009 Joint Scientific Statement as the presence of >= 3 of the following conditions: high blood pressure, high triglycerides, low HDL cholesterol, high fasting glucose, and abdominal obesity. Results: After adjustment for potential confounders, prevalence ratios for metabolic syndrome comparing the highest to the lowest quartiles were 1.41 (95% CI: 1.18-1.67) for the arsenic-inorganic/elemental mercury pattern, 0.95 (0.78-1.16) for the methylmercury-manganese pattern, 0.73 (0.57-0.94) for the cadmium-lead pattern, 0.91 (0.76-1.10) for the copper pattern, and 1.36 (1.13-1.63) for the selenium-zinc pattern. The positive associations observed for the arsenic-inorganic/elemental mercury pattern were due to an elevated prevalence of high blood pressure, low HDL cholesterol, and high triglycerides among those with greater exposures. Associations for the selenium-zinc pattern were driven by a positive relationship with high triglycerides. Greater lead-cadmium co-exposures were related to a lower prevalence of dyslipidemia and abdominal obesity. Conclusions: These cross-sectional findings suggest both toxic and essential metal exposures may contribute to cardiometabolic health, but need to be confirmed with prospective data.