Association between vanadium exposure and children's attention deficit hyperactivity disorder symptoms: A birth cohort study

Background Vanadium is a toxic metal element with a wide range of applications and people can be generally exposed to vanadium. At present, studies investigating the effect of vanadium exposure on offspring's neurodevelopment are scarce.

Objective This study aims to determine vanadium exposure levels of pregnant women and newborns in Ma'anshan city and to explore the association of vanadium exposure with the risk of attention deficit hyperactivity disorder (ADHD) symptoms among children.

Methods The recruitment to the Ma'anshan Birth Cohort was between May 2013 and September 2014. A total of 3 474 women from Ma'anshan Maternal and Child Health Care Center, and 2 922 mother-newborn pairs were finally enrolled in this study. We collected maternal peripheral blood samples during the first and second trimesters and neonatal umbilical cord blood samples. The concentrations of serum vanadium in maternal peripheral blood and neonatal umbilical cord blood were determined by inductively coupled plasma mass spectrometry. Children's ADHD symptom scores were assessed by the Chinese version of the Conners Abbreviated Symptom Questionnaire at follow-up visits of 36-month-old children between October 2016 and April 2018. We converted serum vanadium concentrations by natural logarithm and divided serum vanadium concentrations into low (< P₂₅), medium (P₂₅- < P₇₅), and high (≥P₇₅) level groups according to the distribution of serum vanadium levels. Binary logistic models were performed to analyze the association between exposure to vanadium and the risk of ADHD symptoms among children.

Results The positive rates of vanadium in maternal peripheral serum and neonatal umbilical cord serum were both 100.00%. The M (P₂₅-P₇₅) concentrations of serum vanadium in the first trimester, second trimester, and umbilical cord blood were 1.46 (1.29-1.65), 1.41 (1.20-1.65), and 1.56 (1.31-1.85) μg·L^-1, respectively. The mean child age at the time of ADHD symptoms assessment was (36.28±1.82) months old, and the positive rate of reporting ADHD symptoms was 6.40%. After adjusting for selected confounding factors, the risk of ADHD symptoms among children increased to 4.70 (95% CI： 2.04-10.80) times for each unit increase of natural logarithm of serum vanadium in the first trimester; compared with the low level group, the high level group of serum vanadium in the first trimester showed an increased risk of ADHD symptoms (OR=2.13, 95% CI： 1.33-3.43); the associations between serum vanadium levels in the second trimester and umbilical cord blood and the risk of ADHD symptoms among children showed no statistical significance (all Ps > 0.05). By sex stratification, for each unit increase of natural logarithm of serum vanadium in the first trimester, the risk of ADHD symptoms among boys and girls increased to 3.66 (95% CI： 1.31-10.25) times and 6.73 (95% CI： 1.65-27.40) times, respectively; compared with the low level group, the high level group of serum vanadium in the first trimester had an increased risk of ADHD symptoms in both boys and girls (OR=2.03, 95% CI： 1.14-3.61; OR=2.44, 95% CI： 1.04-5.73); there were no significant correlations between vanadium level in the second trimester and umbilical cord blood and the risk of ADHD symptoms in boys and girls (all Ps > 0.05).

Conclusion The selected pregnant women in Ma'anshan are generally exposed to vanadium; high levels of serum vanadium exposure during the first trimester could increase the risk of ADHD symptoms among children.