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Community Water Fluoridation and Intelligence: Prospective Study in New Zealand
Jonathan M Broadbent1, W Murray Thomson, Sandhya Ramrakha
1Jonathan M. Broadbent and Lyndie A. Foster Page are with the Discipline of Preventive and Restorative Dentistry, Department of Oral Rehabilitation, Faculty of Dentistry, University of Otago, Dunedin, New Zealand. W. Murray Thomson is with the Discipline of Dental Epidemiology and Public Health, Department of Oral Sciences, Faculty of Dentistry, University of Otago. Sandhya Ramrakha, Jiaxu Zeng, and Richie Poulton are with the Dunedin Multidisciplinary Health and Development Study Research Unit, Department of Preventive and Social Medicine, Dunedin School of Medicine, University of Otago. Terrie E. Moffitt is with the Department of Psychology and Neuroscience, Psychiatry and Behavioral Sciences, Duke University, Durham, NC.
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Objectives. This study aimed to clarify the relationship between community water fluoridation (CWF) and IQ. Methods. We conducted a prospective study of a general population sample of those born in Dunedin, New Zealand, between April 1, 1972, and March 30, 1973 (95.4% retention of cohort after 38 years of prospective follow-up). Residence in a CWF area, use of fluoride dentifrice and intake of 0.5-milligram fluoride tablets were assessed in early life (prior to age 5 years); we assessed IQ repeatedly between ages 7 to 13 years and at age 38 years. Results. No clear differences in IQ because of fluoride exposure were noted. These findings held after adjusting for potential confounding variables, including sex, socioeconomic status, breastfeeding, and birth weight (as well as educational attainment for adult IQ outcomes). Conclusions. These findings do not support the assertion that fluoride in the context of CWF programs is neurotoxic. Associations between very high fluoride exposure and low IQ reported in previous studies may have been affected by confounding, particularly by urban or rural status.