Table 7.

Comparison of prospective epidemiological studies

Broadbent et al. (2015)	Green et al. (2019)
Study design
Prospective study Children in areas of residence with and without community water fluoridation (CWF) at age of 3 and/or 5 years General population-based study of children born in Dunedin, New Zealand Complete birth cohort of consecutive births between April 1, 1972–March 31, 1973 with 1037 children (91% of eligible births) and 95.4% retention after 38 years of prospective follow-up Assessment of IQ at ages 7, 9, 11 and 13 years by the Wechsler Adult Intelligence Scale-Revised (averaged into 1 measure) Assessment of IQ at 38 years by the Wechsler Adult Intelligence Scale-Revised test	Prospective study N = 2001 pregnant women were recruited in the MIREC program from 10 cities in Canada between 2008 and 2011. From the children a subset of n = 610 was selected because of “budgetary restraints” Maternal urinary fluoride was measured in urine spot samples at each trimester and a mean was obtained IQ was available in 601 children analyzed between age 3 to 4 years by the Wechsler Primary and Preschool Scale of Intelligence-III Finally, maternal urinary fluoride concentrations and IQ data of the children were available for 512 mother-child pairs
Main result
Fluoride concentrations in drinking water of areas with CWF ranged between 0.7 and 1.0 mg/L (ppm); without CWF between 0.0–0.3 mg/L. Community water fluoridation was not associated with intelligence; the statistical analysis was adjusted for: sex, socioeconomic status, low birth weight, and breastfeeding; analysis of adult IQ also adjusted for educational achievements	Urinary fluoride concentrations of the mothers were 0.51 (0.33–0.62) mg/L (mean; 25th–75th percentile range). An increase of 1 mg/L maternal urinary fluoride was associated with a 4.49 lower IQ score in boys (p = 0.02), but not in girls (p = 0.33). This analysis was adjusted for city, HOME score, maternal education, ethnicity, child sex and prenatal secondhand smoke exposure
Further factors analyzed for an association with IQ
Sex: n.s Socioeconomic status: p < 0.001 Breastfeeding (in areas with CWF): p < 0.001 Low birth weight: p < 0.024 Educational attainment (for adult IQ): p < 0.001 Fluoride toothpaste: n.s Fluoride tablets: n.s	P < 0.001 (girls had 4.95 higher IQ scores than boys) Not reported Not reported Not reported Not reported Not reported Not reported

n.s. not significant