Are high fluoride levels in drinking water associated with hypothyroidism prevalence in England?

Background and aims Studies have suggested that there is a possible link between fluoride exposure and thyroid function. The aim of this study was to examine whether there are differences in the prevalence of hypothyroidism between populations in England living in areas with high and low levels of fluoride in drinking water. Methods We used a cross-sectional study design using secondary data to develop a linear regression model of predictive factors for hypothyroidism prevalence at practice level using fluoride levels in drinking water, hypothyroidism prevalence data, the proportion of registered patients that were female and the proportion of older patients (aged 55+ and 65+). We compared the hypothyroidism prevalence of GP practices in areas with fluoride levels ?0.7mg/l to those with fluoride levels