Developmental Fluoride Neurotoxicity: Clinical Importance versus Statistical Significance
Siamak Sabour, Zahra Ghorbani
School of Dentistry, Shahid Beheshti University of Medical Sciences, Tehran, Iran, E-mail: firstname.lastname@example.org
Environ Health Perspect 121:a70–a70 (2013). http://dx.doi.org/10.1289/ehp.1206192 [Online 1 March 2013]
The author declares they have no actual or potential competing financial interests.
We were interested to read the article by Choi et al. (2012), who investigated the effects of increased fluoride exposure and delayed neurobehavioral development by reviewing published studies and performing a meta-analysis. Of the 39 studies identified, the authors considered 27 to be eligible. Choi et al. reported a mean difference in IQ (intelligence quotient) score between exposed and reference populations of –0.4 (95% confidence interval: –0.5, –0.3) using a random-effects model. Thus, children in high-fluoride areas had significantly lower IQ scores than those who lived in low-fluoride areas.
Even if we ignore the weaknesses of the study (Choi et al. 2012), including a lack of individual-level information and the high probability of confounding because the authors did not adjust for covariates, a difference of 0.4 in mean IQ is clinically negligible (Jeckel et al. 2007; Rothman et al. 2008; Szklo and Nieto 2007) even though it was statistically significant. In general, clinical importance takes priority over statistical significance. The p-value can easily change from significant to nonsignificant because of sample size or the mean difference and standard deviation of the variable in the study population (Jeckel et al. 2007; Rothman et al. 2008; Szklo and Nieto 2007). As Choi et al. (2012) pointed out in their conclusion, there is a “possibility of an adverse effect of high fluoride exposure on children’s neurodevelopment.” Such a conclusion can be considered an ecological fallacy, which can easily lead to misinterpretation of the results. It is important to know that statistics cannot provide a simple substitute for clinical judgment (Jeckel et al. 2007; Rothman et al. 2008; Szklo and Nieto 2007).
Choi AL, Sun G, Zhang Y, Grandjean P. 2012. Developmental fluoride neurotoxicity: a systematic review and meta-analysis. Environ Health Perspect 120:1362–1368.
Jeckel JF, Katz DL, Elmore JG, Wild DMG. 2007. Epidemiology, Biostatistics, and Preventive Medicine. 3rd ed. Philadelphia:Saunders/Elsevier.
Rothman JK, Greenland S, Lash TL. 2008. Modern Epidemiology. 3rd ed. Philadelphia:Wolters Kluwer/Lippincott Williams & Wilkins.
Szklo M, Nieto FJ. 2007. Epidemiology; Beyond the Basics. 2nd ed. Sudbury, MA:Jones and Bartlett.
Notice of Intent to RecruitThe National Institute of Environmental Health Sciences will soon announce a search for candidates for the position of Supervisory Technical Editor (Operations Manager) for EHP. The Operations Manager will report directly to the Editor-in-Chief of EHP. To learn more, read the full notice of intent to recruit.
CEHN October 2014 Article of the Month“Maternal Exposure to Criteria Air Pollutants and Congenital Heart Defects in Offspring: Results from the National Birth Defects Prevention Study” (Environ Health Perspect; DOI:10.1289/ehp.1307289) has been selected by the Children’s Environmental Health Network (CEHN) as its October 2014 Article of the Month. These CEHN summaries discuss the potential policy implications of current children’s environmental health research.
Sign Up to Receive E-mail Alerts
Recent Advance Publications
A Targeted Health Risk Assessment Following the Deep Water Horizon Oil Spill: Polycyclic Aromatic Hydrocarbon Exposure in Vietnamese-American Shrimp Consumers
Commuting-Adjusted Short-Term Health Impact Assessment of Airborne Fine Particles with Uncertainty Quantification via Monte Carlo Simulation
Effects of Benzo[a]pyrene Exposure on Human Hepatocellular Carcinoma Cell Angiogenesis, Metastasis, and NF-κB Signaling
Gene-Specific Differential DNA Methylation and Chronic Arsenic Exposure in an Epigenome-Wide Association Study of Adults in Bangladesh
Prenatal Exposure to Maternal Cigarette Smoking and DNA Methylation: Epigenome-Wide Association in a Discovery Sample of Adolescents and Replication in an Independent Cohort at Birth through 17 Years of Age