Meta-analysis of fluoridation and fractures has been done

EDITOR—The article by McDonagh et al is valuable but not necessarily new in the area of fractures.1 They conclude that the evidence relating fluoridation to fractures is weak and shows no significant effect either way. This is identical to the conclusion that we published in a 1999 meta-analysis not cited by McDonagh et al but listed on Medline.2 This study located 26 studies in this area, compared with their 20, and reported a relative risk for fracture of 1.02 (95% confidence interval 0.96 to 1.09). Interestingly, sex, urbanicity index, and the quality (but not duration) of the study explained 25% of the variation between studies in meta-regression.

Further work in this area will need to be done at an individual level to advance this field, but even this is problematic given the paper by Phipps et al in the same issue of the journal, which reports on a very large cohort of women.3 Nevertheless, it seems unlikely that water fluoridation to 1 ppm has any significant effect on the incidence of fractures at a population level based on the current (albeit weak) evidence.

Critical difference was overlooked

EDITOR—I wish to comment on the paper by McDonagh et al on fluoridation and the study by Phipps et al on bone fracture.1 2 Although the paper by McDonagh et al deals a very serious blow to fluoridation on the basis of their findings of a much lower benefit for caries reduction than previously claimed and a much higher level of dental fluorosis than is acceptable, the authors do not make it clear that dental fluorosis is an indication of a toxic effect of fluoride, in a similar way that the blue line on gums is an indicator of lead poisoning. This raises the question of what other enzymes …