To the Editor.
—I was interested in the article by Danielson et al.1 The authors seem to have obtained a good-sized sample and addressed the shortcomings of the study. I am, however, puzzled by the claim of a significantly increased risk of hip fracture due to artificial fluoridation exposure in both men and women. Although the male subjects exposed to artificial fluoridation did demonstrate a higher relative risk (RR) than those not exposed, the 95% confidence interval (CI) includes 1.00. This would seem to indicate that the increased risk is not statistically significant. Also, an odds ratio (OR) would seem more appropriate than an RR because this study is not prospective in design, as shown by the authors' inability to determine individual prefracture exposures to fluoridation, since such events occurred before the data were recorded.