Abstract
The evidence regarding a potential link of low-to-moderate iodine deficiency, selenium status, and cadmium exposure during pregnancy with neurodevelopment is either contradicting or limited. We aimed to assess the prenatal impact of cadmium, selenium, and iodine on children’s neurodevelopment at 4 years of age. The study included 575 mother–child pairs from the prospective “Rhea” cohort on Crete, Greece. Exposure to cadmium, selenium and iodine was assessed by concentrations in the mother’s urine during pregnancy (median 13 weeks), measured by ICPMS. The McCarthy Scales of Children’s Abilities was used to assess children’s general cognitive score and seven different sub-scales. In multivariable-adjusted regression analysis, elevated urinary cadmium concentrations (≥0.8 µg/L) were inversely associated with children’s general cognitive score [mean change: −6.1 points (95 % CI −12; −0.33) per doubling of urinary cadmium; corresponding to ~0.4 SD]. Stratifying by smoking status (p for interaction 0.014), the association was restricted to smokers. Urinary selenium was positively associated with children’s general cognitive score [mean change: 2.2 points (95 % CI −0.38; 4.8) per doubling of urinary selenium; ~0.1 SD], although the association was not statistically significant. Urinary iodine (median 172 µg/L) was not associated with children’s general cognitive score. In conclusion, elevated cadmium exposure in pregnancy of smoking women was inversely associated with the children’s cognitive function at pre-school age. The results indicate that cadmium may adversely affect neurodevelopment at doses commonly found in smokers, or that there is an interaction with other toxicants in tobacco smoke. Additionally, possible residual confounding cannot be ruled out.Electronic supplementary materialThe online version of this article (doi:10.1007/s10654-016-0151-9) contains supplementary material, which is available to authorized users.
Highlights
Millions of children worldwide never reach their full neurodevelopmental potential
The present findings support a few previous studies indicating that elevated cadmium exposure during pregnancy may be inversely associated with children’s cognitive function measured at pre-school age
We found a significant interaction between the mother’s urinary cadmium concentration and smoking status, and further stratification showed that only children born to mothers who smoked during pregnancy, and had higher exposure levels, appeared affected
Summary
The numbers of environmental chemicals that have been associated with neurodevelopmental toxicity are steadily increasing [1, 2]. Toxic trace elements, such as lead, methylmercury, arsenic and manganese have repeatedly been shown to impair neurodevelopment [2, 3]. A systematic review and meta-analysis [3], covering studies between January 2000 and March 2012, identified four studies exploring an association between cadmium exposure and neurodevelopment, but only one study had measured the prenatal exposure This Chinese study, found an inverse association between the children’s prenatal cadmium exposure, assessed by concentrations in cord blood, and full scale IQ at 4.5 years [4]. The conflicting findings may be a result of low power in several studies, the use of different developmental tests, and differences in diet and nutritional status
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