Fluoride in drinking water and risk of hip fracture in the UK: a case-control study

Background Although the benefits of water fluoridation for dental health ar e widely accepted, concerns remain about possible adverse effects, particul arly effects on bone. Several investigators have suggested increased rates of hip fracture in places with high concentrations of fluoride in drinking water, but this finding has not been consistent, possibly because of unreco gnised confounding effects. Methods We did a case-control study of men and women aged 50 years and olde r from the English county of Cleveland, and compared patients with hip frac ture with community controls. Current addresses were ascertained for all pa rticipants; for those who agreed to an interview and who passed a mental te st, more detailed information was obtained about lifetime residential histo ry and exposure to other known and suspected risk factors for hip fracture. Exposures to fluoride in water were estimated from the residential histori es and from information provided by water suppliers. Analysis was by logist ic regression. Findings 914 cases and 1196 controls were identified, of whom 514 and 527, respectively, were interviewed. Among those interviewed, hip fracture was s trongly associated with low body-mass index (p for trend <0.001) and physic al inactivity (p for trend <0.001). Estimated average lifetime exposure to fluoride in drinking water ranged from 0.15 to 1.79 ppm. Current residence in Hartlepool was a good indicator for high lifetime exposure to fluoride, After adjustment for potential confounders, the odds ratio associated with an average lifetime exposure to fluoride greater than or equal to 0.9 ppm w as 1.0 [95% CI 0.7-1.5]. Interpretation There is a low risk of hip fracture for people ingesting flu oride in drinking water at concentrations of about 1 ppm. This low risk sho uld not be a reason for withholding fluoridation of water supplies.