title: Are fluoride levels in drinking water associated with hypothyroidism prevalence in England? A large observational study of GP practice data and fluoride levels in drinking water.
abstract: BACKGROUND
  While previous research has suggested that there is an association between fluoride ingestion and the incidence of hypothyroidism, few population level studies have been undertaken. In England, approximately 10% of the population live in areas with community fluoridation schemes and hypothyroidism prevalence can be assessed from general practice data. This observational study examines the association between levels of fluoride in water supplies with practice level hypothyroidism prevalence.
  
  
  METHODS
  We used a cross-sectional study design using secondary data to develop binary logistic regression models of predictive factors for hypothyroidism prevalence at practice level using 2012 data on fluoride levels in drinking water, 2012/2013 Quality and Outcomes Framework (QOF) diagnosed hypothyroidism prevalence data, 2013 General Practitioner registered patient numbers and 2012 practice level Index of Multiple Deprivation scores.
  
  
  RESULTS
  We found that higher levels of fluoride in drinking water provide a useful contribution for predicting prevalence of hypothyroidism. We found that practices located in the West Midlands (a wholly fluoridated area) are nearly twice as likely to report high hypothyroidism prevalence in comparison to Greater Manchester (non-fluoridated area).
  
  
  CONCLUSIONS
  In many areas of the world, hypothyroidism is a major health concern and in addition to other factors-such as iodine deficiency-fluoride exposure should be considered as a contributing factor. The findings of the study raise particular concerns about the validity of community fluoridation as a safe public health measure.
authors.affiliation: Centre for Health Services Studies, University of Kent, Canterbury, Kent, UK.
authors.forename: S
authors.identifier: http://orcid.org/0000-0002-7002-2614
authors.initials: S
authors.lastname: Peckham
authors.affiliation: Centre for Health Services Studies, University of Kent, Canterbury, Kent, UK.
authors.forename: D
authors.initials: D
authors.lastname: Lowery
authors.affiliation: Centre for Health Services Studies, University of Kent, Canterbury, Kent, UK.
authors.forename: S
authors.initials: S
authors.lastname: Spencer
mesh_terms: D000328:Adult; D017677:Age Distribution; D003430:Cross-Sectional Studies; D060766:Drinking Water / Q000009:adverse effects* / Q000737:chemistry*; D004739:England / Q000453:epidemiology; D005260:Female; D005457:Fluoridation / Q000009:adverse effects* / Q000706:statistics & numerical data; D058006:General Practice / Q000706:statistics & numerical data; D006801:Humans; D007037:Hypothyroidism / Q000139:chemically induced* / Q000453:epidemiology; D016015:Logistic Models; D008297:Male; D015995:Prevalence; D017678:Sex Distribution
chemical_list: D060766:Drinking Water
keywords: ENDOCRINOLOGY; EPIDEMIOLOGY; PUBLIC HEALTH POLICY