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Heavy metals, including cadmium, are suspected to increase serum uric acid levels and hyperuricemia in both gender, but the evidences about this are inconclusive. To determine whether serum cadmium in American adults(≥19 years old) is associated with uric acid levels and risk of hyperuricemia, 2620 participants from the US National Health and Nutrition Examination Survey were recruited. Hyperuricemia was defined as a serum UA concentration ≥ 416.4 μmol/L for men and ≥ 356.9 μmol/L for women. Regression analyses were used to analyze the association of cadmium with serum UA and hyperuricemia. The threshold effect explored using two-piecewise linear regression model by the smoothing plot. The overall median of blood cadmium was 0.27 μg/L in men and 0.33μg/L in women. After adjusting for the covariates (race; age; education; BMI; smoke status; alcohol consumption; blood lead; hypertension; diabetes mellitus; hemoglobin; eGFR; triglyceride; and cholesterol), a non-linear relationship between hyperuricemia and cadmium among men was detected; and there was a positive line correlation between them for women (OR = 1.58; 95%CI (1.08, 2.31)). No significant association between uric acid and cadmium in either gender was found. Blood cadmium levels in the range currently considered acceptable were positively associated with increased prevalence of hyperuricemia in women, but inversely associated in men (cadmium <0.77μg/L)., (© 2021. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

Exposure to excessive fluoride has been associated with a number of adverse health outcomes; however, there is a lack of evidence on the relation between fluoride exposure and serum uric acid levels, especially in human populations. The present study examined a potential relationship between fluoride exposure, measured as both plasma and water fluoride concentrations, and uric acid levels in an adolescent population. A nationally representative subsample of 1933 adolescents, aged 12-19 years, in the 2013-2016 National Health and Nutrition Examination Survey was analyzed for the association of fluoride concentrations with serum uric acid levels using multivariate general linear and logistic regression models, adjusting for potential confounders. Since uric acid levels change during development, hyperuricemia was defined in this study as over the mean plus one standard deviation for each sex and age group of adolescents. Of the study participants, 276 adolescents (weighted prevalence, 16.56%) had hyperuricemia. A significant and dose-dependent increase in prevalence of hyperuricemia was seen among the participants cross increasing quartiles of plasma fluoride (p-trend = 0.0017). After adjusting for potential confounders, we found that adolescents in the higher quartiles of plasma fluoride (≥0.32 µmol/L) and in the highest quartile of water fluoride (≥0.73 mg/L) had significantly increased odds of hyperuricemia compared with those in the lowest quartile. A 1.95-fold increased odds (95% CI: 1.37, 2.77) of hyperuricemia was also observed when analyzing plasma fluoride concentrations as continuous variable. A general linear model revealed that a 1 µmol/L increase in ln-plasma fluoride was associated with a 0.212 mg/dL (p < 0.0001) increased serum uric acid level. Furthermore, a positive relationship was observed between water and plasma fluoride concentrations (β = 0.1907; p < 0.0001). Our study demonstrates a potential relation between fluoride exposure and hyperuricemia in adolescents. Further studies are warranted to overcome the limitations of this study to examine the impact of long-term exposure to low levels of fluoride during development on hyperuricemia and its related health outcomes., (Copyright © 2020 The Authors. Published by Elsevier Inc. All rights reserved.)