By Ken Perrott 24/09/2015


Image Credit: Cochrane Oral Health Blog

The latest Cochrane Review on community water fluoridation (CWF) was published in June. Here are a citation and link for those interested:

Iheozor-Ejiofor, Z., Worthington, HV., Walsh, T., O’Malley, L., Clarkson, JE., Macey, R., Alam, R., Tugwell, P., Welch, V., Glenny, A. (2015). Water fluoridation for the prevention of dental caries (Review). The Cochrane Library, (6).

Immediately after publication, anti-fluoride propagandists launched a campaign of misrepresentation and outright distortion of the review’s findings. I dealt with some of this, and commented on the review itself, in the following posts:

The wave of misrepresentation and situations concerned health professionals – some of their on-line feedback and responses are in the Cochrane blog posts – Little contemporary evidence to evaluate effectiveness of fluoride in the water and Our response to the feedback on the Cochrane fluoridation review).

The Cochrane Oral Health Group yesterday published an updated Plain Language Summary (PLS) for the review. If you want to look in detail here is the original version of the review, and here is the abstract and updated Plain Language Summary from the latest version (now online). Their short explanation for this is:

“Following feedback, from a variety of sources, we felt it was necessary to make the language of the PLS simpler.”

This is logical. The PLS is the only part of the Review most policy makers will read. The old version contained too many words like “bias” and references to research “quality” which may have been reasonable to an academic audience but conveyed an entirely different meaning to policy makers who do not have an academic or scientific background. Anti-fluoride campaigners have worked hard to use this in their misrepresentations and distortions aimed at policy makers as well as the public.

Some of the changes

The new PLS does not include the word “bias” and now describes the selection criteria pointing out most studies made after 1975 were excluded (because they did not include initial surveys). Readers will now be more aware that the lack of information in some areas resulted from these strict selection criteria and not from lack of research.

For example, the text:

“No studies met the review’s inclusion criteria that investigated the effectiveness of water fluoridation for preventing tooth decay in adults, rather than children”

has been replaced by

“Within the ‘before and after’ studies we were looking for, we did not find any on the benefits of fluoridated water for adults.”

And the text:

“There was insufficient information available to find out whether the introduction of a water fluoridation programme changed existing differences”

has been replaced by:

“We found insufficient information to determine whether fluoridation reduces differences in tooth decay levels between children from
poorer and more affluent backgrounds.”

Will the misrepresentation continue?

Of course it will. Even the most carefully worded summary can be distorted to misrepresent reported findings. Hopefully, though, these changes will make it harder for campaigners to pull the wool over the eyes of policy makers. The careful reader will now have a better idea of the limitations of the review resulting from the strict selection criteria. Hopefully, they will also be aware that statements like “We found insufficient information . . .” do not mean there is no information. Nor does the inability, within the restricted selection criteria, to find an effect mean there is no effect.

I am disappointed that their changes did not make the situation of dental fluorosis clearer. They do now stress that most of the dental fluorosis studies reviewed “were conducted in places with naturally occurring – not added – fluoride in their water.” But this is not adequate:

“results of the studies reviewed suggest that, where the fluoride level in water is 0.7 ppm, there is a chance of around 12% of people having dental fluorosis that may cause concern about how their teeth look.”

is just not adequate

The choice of 0.7 ppm will be seen as relevant to the concentration used in CWF – but this does not mention that any difference between the  prevalence in fluoridated and unfluoridated areas is very small and not statistically significant. In other words, their comments on dental fluorosis are still not relevant to CWF.

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