SIR, – In your annotation (Jan 28, p. 203) the preventive action of fluorides on osteoporosis is said to be confirmed by the recent findings of Bernstein et al. While it is quite possible that fluorides may have such an effect, the cited article has several deficiencies which in my opinion are severe enough to cast doubt on the validity of the results.
Of the factors known to influence the development and severity of involutional osteoporosis, age is of prime importance. In the paper under scrutiny, the material has been divided into age-groups without specifying the average ages within the groups. For statistical evaluation between the groups, this omission is particularly serious for the age group of 65 + years, because of possible wide age-variations upward, and especially because the high-fluoride group included only 38 male and 42 female subjects. A difference in the mean age of as little as 5 years between the high-fluoride and low-fluoride groups might be responsible for the entire statistical significance in differences of bone density and of percentage of compressed vertebrae between the two groups.
Secondly, it is most unusual and contrary to all previous experience that male populations should have a higher rate of severe osteoporosis than females. The extraordinary incidence of spinal compressions in males over 65 years old of about 50% indicates that the given study-population in general does not confirm to populations elsewhere as to the incidence of osteoporosis. Therefore, some other unknown (and unusual) factors may have been influencing the results. It is somewhat paradoxical that prevention of osteoporosis by administration of fluorides is suggested by a study in which men had more severe osteoporosis than women, and yet no difference was found in the prevalence of osteoporosis between the male subjects in the high and low fluoride areas.
These criticisms are not so much directed against Bernstein et al., who have made a good effort to solve a difficult problem, as against the too easy acceptance of early or preliminary results.