Abstract

Excerpts:

Our study has several strengths. So far as we know, this is the first epidemiological study to uncover the effect modification of DAT1 and MAOA gene polymorphism in the relationship between fluoride exposure and IQ, and the first study to analyze the high-dimensional interaction among fluoride exposure and the four DA relative genes. Our findings suggest a novel clue for the neuro-toxicological mechanism of fluoride.

Our study also has some limitations. We used urinary fluoride to represent the fluoride exposure from drinking water, which ignored the bias of short-term fluoride intake from diet. However, our finding could still reveal the health effects of internal fluoride exposure. Due to the cross-sectional design, our results are not strong for causal demonstration. Small sample size also limited the statistical power. Further prospective studies with larger sample size are essential to validate our findings. Nevertheless, the effect modification of DA relative genes and interaction among UF and these genes are still noteworthy.

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Appendix A. Supplementary material

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Table 1. Basic characteristics of study population.

Characteristics	Mean ±?SD or n (%)
Sample size	567
Age (years old)	9.15?±?1.02
Gender
Boys	284 (50.1)
Girls	283 (49.9)
Body mass index (kg/m2)	17.76?±?3.55
Paternal education level
<high school	162 (28.6)
?high school	405 (71.4)
Maternal education level
<?high school	177 (31.2)
??high school	390 (68.8)
Household income (RMB/year)
??30,000	135 (23.8)
30,000–100,000	303 (53.4)
>?100,000	129 (22.8)
Maternal age at delivery (years old)
??30	365 (64.4)
>?30	202 (35.6)
Abnormal birth
no	461 (81.3)
yes	106 (18.7)
Log_UF	0.015 (0.252)
IQ scores	112.17 (11.75)

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