Cochrane responds to misrepresentation of their fluoridation review


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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12 responses to “Cochrane responds to misrepresentation of their fluoridation review

  1. Wow, the Parachute bloggist really does want to have his cake and eat it too!
    Where the alterations to the summary of the Cochrane Review fit his leaning, he congratulates them. Where it goes against his pre-existing biases, instead of admitting that he might be in error he criticises the Cochrane reviewers. I guess Mr Parachute will never be happy until every one of his existing views on the advisability of artificially fluoridating water supplies is confirmed by a review. Any reviews that come to contrary conclusions to what he has ossified in his thinking will apparently be criticised as inadequate or wrong.


  2. David, my approach results from an objective analysis and analysing the review and changes to the PLS critically and intelligently.

    How about you specifically debating the points I have made in an intelligent way instead of floating a straw man?

    Liked by 1 person

  3. Wow, David Mcrae’s difficulty in comprehension runs to not even being able to identify Ken Perrott as being the author of this blog.


  4. Ken
    You say that
    The new PLS does not include the word “bias”
    but I can find seven.
    Two of them refer to Cochrane’s ‘Risk of bias’ tool and the other five to risks of bias associated with studies.


  5. Go have a check using a search tool, Ross. I couldn’t find any occurrence in the Plain Language Summary but the Abstract hasn’t been changed so the word is still in that.



  6. You are right. My word search unwittingly stopped short of the PLS but how does the revised PLS without ‘bias’ weaken the unchanged Abstract or the 274 page full report which includes nearly 1,000 uses of ‘bias’ – admittedly many of them as a component of headings.
    All documents seem to me to be pretty lukewarm about the efficacy of CWF.


  7. The problem is that the PLS is aimed at policy makers who may not have a background in science and, therefore, cannot make a proper assessment of the full text or abstract. Hence, they get the wrong idea from words like “bias”, research quality and the limitations imposed by selection criteria.

    Someone familiar with the science, and particularly scientific assessment of social policies, can take all these qualifications into account – as indeed the full text of the document does in its comments.

    I suspect you do not understand this aspect – from your statement about the temperature of documents. Proper assessment of such research must be based on real world possibilities. Unfortunately the quality criteria (and selection criteria) was suitable for clinical drug trials, but not social health measures. A point the document itself made in its discussion.


  8. An increasing number of knowledgeable people are questioning the foundation science on which CWF has been built. Given the following extract the only surprise I have is that die hard defenders of CWF are still fighting a rear-guard action:
    The distortion abuse and misuse of science in the recent VW emissions debacle has a parallel in the issue of fluoridating our drinking water.
    “Sugar Industry’s Influence on the Policies on Sugars (From Journal of Dental Research October 2015)
    The sugar, food, and drink industries protect themselves from potentially damaging information and research suitable for policy makers by lobbying and influencing research policy
    (Kearns et al. 2015). Denying evidence that sugars are harmful to health has always been at the heart of the sugar industry’s defence. The industry’s tactic is to undermine all the scientific
    evidence by supporting scientists who offer contrary evidence, thereby creating a “controversy.” They also fudge and offer contrary evidence to delay any policy decisions and manipulate
    governments to procrastinate (Bes-Rastrollo et al. 2013; Goldman et al. 2014). Their influence on national and international committees is considerable (Kearns et al. 2015).
    The World Sugar Research Organisation, representing sugar industry interests, successfully blocked the 1990 and 2003 WHO / Food and Agriculture Organization joint committees’ recommendations
    on sugars from becoming WHO policy, as we know from personal experience and as noted by Kearns et al. (2015). Kearns et al. also showed how the sugar industry
    funded research on a vaccine against tooth decay with questionable potential for widespread application. It influenced policy in the US National Institute of Dental Research, which
    changed the proposals for the National Caries Program to exclude the proposal to restrict sugars consumption to prevent caries (Kearns et al. 2015).”
    Unfortunately our politicians seem more focused on flags and Pandas rather than on an issue that is causing real harm to a significant number of people.


  9. for an absent friend …

    Anti fluoridation lobby groups and alternative health industry protect themselves from potentially damaging information and research suitable for policy makers by lobbying and influencing research policy.
    Denying the evidence that CWF is harmless to health has always been at the heart of the anti fluoridation lobby groups and the alternative health industry’s approach. The industry’s tactic is to undermine all the accepted scientific evidence by supporting scientists who offer contrary evidence, thereby creating a “controversy.” They also fudge and offer contrary evidence to delay any policy decisions and manipulate governments to procrastinate . Their influence on scientifically uninformed policy committees can be of some concern.

    Anti fluoridationist activists are informed by personal experience, social media, blogs and Facebook posts. Also known is how the alternative medicine industry
    funded research published in non reputable journals. Fortunately, these fail to influence policy in the US National Institute of Dental Research, and failed to
    change proposals within the National Caries Program.

    Fortunately our politicians seem are inattentive to this lobbying as CWF is proven to be protecting the dental health of a significant number of people.



  10. David Fierstien

    Trevor Crosby says: “An increasing number of knowledgeable people are questioning the foundation science on which CWF has been built. Given the following extract the only surprise I have is that die hard defenders of CWF are still fighting a rear-guard action.”

    I wonder what planet Trevor has been living on. The following is a portion of an email to me from Mr. Kip Duchon, National Fluoridation Engineer at the CDC.

    ” . . one of the organizations that oppose fluoridation has a list of professionals, about 4500, who have signed the opposition to fluoridation statement. In the U.S. there are over 860,000 physicians, 2.8 million nurses, nearly 170,000 dentists and about 3.2 million PhD’s, or about 7 million. If the list is accurate, then 0.064% or 1 in every 1555 oppose fluoridation. I understand that about 25% of the US list of Professionals Opposed to fluoridation are from outside the US, so the actual percentages opposing fluoridation might be even lower if that is the case. As I said in the beginning of this message, there is no accurate assessment of professionals opposed to fluoridation, and this would be as crude as any analysis, but maybe it puts that in perspective.”


  11. The links to the Cochrane blog go nowhere. And regardless of what language they are using, does it not still say that after more than 50 years of study, they still cannot vouch for fluoride’s safety or effectiveness – in large part because of the poor quality of past reports and studies? The York review found the same thing 15 years ago.


  12. Yes, Shaman, apparently they have removed their blog, or at least this discussion.

    The review considered only efficacy – it did not consider “safety” or health issues. And it is not a matter of “vouching” for anything – their job was to review the literature.

    If you read the review itself, and particularly the discussion, you will see the authors acknowledge that their selection criteria and criteria for judgement of “quality” was not really appropriate for a social health measure where double-blind controlled studies are impossible.

    Unfortunately, these qualifications did not make it to the abstract or original plain language summary and this provided scope for misrepresentation of the review’s findings. Feedback pointing this out resulting in a rewrite of the plain language summary.

    I have no idea why the blog or blog articles have been removed and think it rather poor, ethically, for them not to have provided explanations.


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