Developmental Fluoride Neurotoxicity: Choi et al. Respond
Anna L. Choi1, Philippe Grandjean1, Guifan Sun2, Ying Zhang2
1Harvard School of Public Health, Boston, Massachusetts, E-mail: firstname.lastname@example.org; 2China Medical University, Shenyang, China
Environ Health Perspect 121:a70–a70 (2013). http://dx.doi.org/10.1289/ehp.1206192R [Online 1 March 2013]
The author declares they have no actual or potential competing financial interests.
Sabour and Ghorbani’s comments about the reported mean difference in IQ (intelligence quotient) scores reported in our article (Choi et al. 2012) suggest a misunderstanding of the scale unit we used and the public health significance of even a small decrease in the average IQ associated with exposure. We appreciate this opportunity to clarify the factual information about the reported IQ measure.
The standardized weighted mean difference (SMD) in IQ score between exposed and reference populations was –0.45 (95% confidence interval: –0.56, –0.35) using a random-effects model (Choi et al. 2012). We used the SMD because the studies we included used different scales to measure the general intelligence. The SMD is a weighted mean difference standardized across studies, giving the average difference in standard deviations for the measure of that outcome. For commonly used IQ scores with a mean of 100 and an SD of 15, 0.45 SDs is equivalent to 6.75 points (rounded to 7 points). As research on other neurotoxicants has shown, a shift to the left of IQ distributions in a population will have substantial impacts, especially among those in the high and low ranges of the IQ distribution (Bellinger 2007).
Bellinger BC. 2007. Interpretation of small effect sizes in occupational and environmental neurotoxicity: individual versus population risk. Neurotoxicology 28:245–251.
Choi AL, Sun G, Zhang Y, Grandjean P. 2012. Developmental fluoride neurotoxicity: a systematic review and meta-analysis. Environ Health Perspect 120:1362–1368.
Introducing Children’s Health Collection 2014
EHP’s fifth annual Children’s Health Collection is now available. The collection comprises abstracts of all relevant articles published in EHP from October 2013 through September 2014: peer-reviewed research articles, news features, Science Selections, and editorials.
ISEE 2014 Abstracts Now Available
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CEHN November 2014 Article of the Month
“Asthma in Inner-City Children at 5–11 Years of Age and Prenatal Exposure to Phthalates: The Columbia Center for Children’s Environmental Health Cohort” (Environ Health Perspect; DOI:10.1289/ehp.1307670) has been selected by the Children’s Environmental Health Network (CEHN) as its November 2014 Article of the Month. These CEHN summaries discuss the potential policy implications of current children’s environmental health research.
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