Associations of Urinary and Blood Trace Elements with Diabetes Mellitus in US Adults: A Cross-Sectional NHANES 2013–2014 Analysis

INTRODUCTION: Environmental trace element exposure has been proposed as a modifiable risk factor for type 2 diabetes mellitus (DM), but findings are inconsistent. We examined associations between urinary and blood trace elements and DM, and their sensitivity to model specification.
METHODS: We analysed 1,486 adults aged 20 years or older from the 2013–2014 NHANES cycle. DM was defined by American Diabetes Association criteria. Seventeen urinary and five blood elements were measured by mass spectrometry. Groups were compared using Mann–Whitney U and chi-square tests with Benjamini–Hochberg correction. Log-transformed concentrations were entered into logistic regression models adjusted for age, sex, body mass index, race/ethnicity, socioeconomic position, smoking, hypertension, and kidney disease, fitted with and without complex survey weights. Odds ratios (OR) are reported per interquartile-range increase.
RESULTS: DM prevalence was 13.7%. In adjusted models (n=1,388), urinary arsenous acid was inversely associated with DM (OR 0.55, 95% CI 0.36–0.86, p=0.008); this persisted under the survey design (OR 0.47, 0.30–0.72, p<0.001) and after creatinine adjustment. Urinary cadmium, strongly associated when age was omitted (OR 1.56, 1.17–2.07, p=0.002), showed no association after adjustment for age (OR 0.89, 0.65–1.23, p=0.481). Blood selenium was associated in the unweighted analysis (OR 1.26, p=0.020) but not in the weighted analysis; urinary tin and molybdenum were only associated under the survey design.
DISCUSSION AND CONCLUSION: The cadmium–DM association was fully attributable to age confounding, and arsenous acid showed an inverse rather than positive association. Such associations are highly sensitive to model specification; adequate age adjustment and use of the complex survey design are essential in NHANES-based analyses.

Keywords: Trace elements, environmental exposure, diabetes mellitus, nutrition surveys, confounding factors, epidemiologic.