Association of urinary metals levels with obesity in urban preschoolers in Shiyan of Hubei Province

Background Metal exposure is associated with obesity in adults, but evidence from studies on preschool children is insufficient.

Objective This study is designed to analyze the relationship between urinary metal levels and obesity in preschool children.

Methods In the cross-sectional study, a questionnaire survey and a physical examination were conducted among 1 595 preschoolers in Shiyan of Hubei Province. According to the standards of the World Health Organization, body mass index (BMI) ≥ the 95th (P₉₅) percentile for their age and sex is considered to be obese. The urinary concentrations of 24 metals were determined by inductively coupled plasma mass spectrometry. The participants were divided into Q1 to Q4 groups according to the quartiles of urinary metal concentrations. The relationships between exposure levels to mono-metals and poly-metals and obesity in the preschoolers were evaluated by binary logistic models, and variables in the polymetallic exposure model were screened by Lasso regression.

Results A total of 1 471 children were included in this study, with a mean age of (4.4±1.0) years, and boys accounted for 55.6%. The overall obesity rate was 11.8%. In single-metal models that was adjusted for obesity-related factors (such as sex, age, birth weight), the risks of obesity for children in the vanadium, copper, manganese, and uranium Q3 groups were 52%, 56%, 55%, and 75% of those in the Q1 groups; the risks of obesity for children in the molybdenum, vanadium, rubidium, aluminum, cadmium, arsenic, uranium, and thallium Q4 groups were 54%, 56%, 59%, 52%, 50%, 39%, 73%, and 55% of those in the Q1 groups, respectively; except copper and manganese, above metals had a linear trend with the risk of childhood obesity (P_trend < 0.05). Six metals such as vanadium, aluminum, cadmium, arsenic, uranium, and titanium selected by LASSO regression were included in the polymetallic exposure model, and the results showed that the risk of obesity for children in the arsenic Q4 group was 50% (95% CI: 0.28-0.87) of that in the Q1 group, and there was still a linear trend (P_trend=0.046); the risk of obesity for children in the uranium Q3 group was 53% (95% CI: 0.31-0.91) of that in the Q1 group, but there was no linear trend (P_trend=0.131).

Conclusion Some urinary metal levels are negatively correlated with obesity of preschool children in Shiyan city of Hubei province, among which arsenic and uranium may be potential critical influencing factors for obesity.