Urine metals concentrations and dyslexia among children in China.

BACKGROUND: Exposures to heavy metals has been linked to many developmental disorders. However, few studies have investigated the effects of exposure and co-exposure to metals on dyslexia, especially with regard to dyslexics in China. OBJECTIVES: To investigate the association between urine metal concentrations and dyslexia in a case-control study among children in China. METHODS: A case-control study was conducted in the Tongji Reading Environment and Dyslexia (READ) research program. A total of 228 dyslexics and 228 controls were matched on gender, age (within one year), and grade. The concentrations of 21 urine metals were measured by an inductively coupled plasma-mass spectrometer (ICP-MS). Multivariable conditional logistic regression models were applied to estimate the adjusted odds ratios (ORs) of Chinese dyslexia. RESULTS: After adjusting for potential confounders, two metals (selenium and argentum) were significantly associated with dyslexia in single-metal multivariable models. Argentum was positively associated with the risk of dyslexia, while selenium was negatively associated. In the multiple-metal model, compared with extreme quartiles, the ORs (95% CIs) for selenium was 0.36 (95% CI: 0.14-0.93; Ptrend = 0.029). In the joint association analysis, children with higher levels of urine argentum and lower level of urine selenium had a significantly higher risk of dyslexia than those with low levels of argentum and selenium (OR = 5.06, 95% CI: 1.67-18.84). CONCLUSIONS: The findings suggest that exposure to selenium and argentum may relate to dyslexia in China. Longitudinal studies are needed to further evaluate these relationships and investigate potential mechanisms.