Re: Letter to the Editor of Public Health in response to ‘Association……’? between low fluoride exposure and children’s intelligence: A meta-analysis relevant to community water fluoridation’

Abstract

Section snippets

Registration of the protocol
The protocol for meta-analysis was published in PROSPERO (CRD42022315263) and included in the PRISMA checklist. We acknowledge this oversight and recognize that including this information in the publication would have helped the readers.

Study selection process
Regarding the study selection process, we list in Fig. 1 the reasons for excluding 51 publications. Our research question was: Does fluoride exposure recommended for caries prevention decrease children’s cognition and IQ scores? Therefore, we focused on studies where we could demonstrate that fluoride exposure was less than ?1.5 mg/L in water. Exposure to water supplies above this level of fluoride is known to be associated with severe enamel fluorosis or skeletal fluorosis, such that it can be

Risk-of-bias assessment (RoB)
In general, systematic review protocols that address etiological questions about the relationship between exposure and outcome exclude all cross-sectional and ecological studies.18 For example, Karipidis et al. used the OHAT RoB tool to determine the effect of exposure to radiofrequency fields on cancer risk.19 They excluded all cross-sectional and ecological studies because these study designs do not allow for calculating the intended measures of effect. Eick et al. found that using different

Details of the supplemental analysis
Due to the limited number of words and figures, we could not provide the details of all the analyses in the text. The relationship between fluoride (F) concentration in water or urine and IQ was explored in eight studies. Supplementary Figure B shows no significant fluctuation of SMD in IQ scores across the differences in fluoride concentrations by non-linear modeling with restricted cubic spline meta-regression (P = 0.21) with three knots at 10, 50, and 90th percentiles. The model was weighted

Lack of effect or inherent difficulty in observing an adverse effect at lower exposure levels
The reader’s statement that the supplementary Figures B and C confirm the inherent difficulty in observing an adverse effect at lower exposure levels seems to be hypothesizing after the results are known, a questionable research practice. The difference in the prevalence of dental fluorosis and severity of caries between fluoridated and non-fluoridated communities demonstrate that the effect of fluoride is observable at lower exposure levels if it is present.5,28 According to Green et al.,

ONLINE AT https://www.sciencedirect.com/science/article/abs/pii/S0033350625000356?via%3Dihub

Authors and Affiliations

Jayanth V. Kumar, California Department of Public Health (Retired), 13521 Petrel St., Clarksburg, MD, 20871, USA

lMark E. Moss

Mark E. Moss, ECU School of Dental Medicine, 1851 MacGregor Downs Road – MS 701, East Carolina University, Greenville, NC, 27834-4354, USA

lHonghu Liu

Honghu Liu, Public & Population Health, Department of Medicine, University of California, Los Angeles (UCLA), USA

Susan Fisher-Owens

Susan Fisher-Owens, School of Medicine and School of Dentistry, University of California, San Francisco, 1001 Potrero Ave, San Francisco, CA, 94110, USA

Received 9 January 2025, Accepted 20 January 2025, Available online 17 February 2025.