Community water fluoridation and health outcomes in England: a cross-sectional study.

Abstract

Six million people in England live in areas where the level of fluoride in water is adjusted to reduce the significant public health burden of dental caries. The dental effects of fluoride are well established, but evidence for suggested adverse health effects is limited, with a lack of rigorous small area population studies that control for confounding. This study aims to test the association between water fluoridation schemes and selected health outcomes using the best available routine data sources. Ecological level exposure to fluoridated water was estimated for standard small areas and administrative districts in England using Geographical Information Systems and digitized boundaries based on known patterns of water supply. The association between fluoridation and dental and nondental health indicators was tested using multivariable regression models including ecological level confounding variables. Health indicator data were obtained from routine sources. There was strong evidence of lower prevalence of dental caries (P<0.001) among children living in fluoridated areas, they also had fewer teeth affected on average (P<0.001), and lower admission rates for tooth extraction (55% lower; 95% CI-73%, -27%; P=0.001). There was no strong evidence of an association between fluoridation and hip fracture, Down syndrome, all-cancer, all-cause mortality or osteosarcoma. Fluoridation was negatively associated with the incidence of renal stones (7.9% lower; 95% CI-9.6%,-6.2%; P<0.001) and bladder cancer (8.0% lower; 95% CI-9.9%,-6.0%; P<0.001). This study uses the comprehensive data sets available in England to provide reassurance that fluoridation is a safe and highly effective public health measure to reduce dental decay. Although lower rates of certain nondental outcomes were found in fluoridated areas, the ecological, observational design prohibits any conclusions being drawn regarding a protective role of fluoridation.