Tag Archives: scientific critique

Experts complain to funding body about quality of fluoride-IQ research

Science should never be protected from critical and rational discussion. Funding bodies should also be aware of problems in the research they fund. Image credit: The value of experience in criticizing research.

The scientific community was generally critical of the recent Canadian maternal neonatal fluoride – child IQ research (see expert reaction to study looking at maternal exposure to fluoride and IQ in children). But this has now taken a more serious turn.  Thirty academics and professional experts from health and dental institutions in the US, Canada, UK, Ireland, and Australia have formally complained to the US National Insitute of Environmental Health Science (NEHS) about the study.

This is highly important as the NEHS is the funding body for this research. If it takes seriously the criticisms of poor quality of the research and its bias it could well mean these study authors lose their funding.

I have covered professional criticism of this study in previous articles (and included some of my own critical comments). See:

Here is the letter to the NIEHS – readers can download and read it for themselves. I urge you to do this as there may well be a lot of misrepresentation circulating in the near future if anti-fluoride activists launch a campaign to discredit it.

Release of data and methodology requested

The letter requests the NIEHS:

“formally ask the Green authors to release the HIPAA-compliant, Research Identifiable File (RIF) data sets from their study, as well as a complete explanation of their methods and the computer program/codes used in their data management and analysis.”

This request is motivated by the fact that several of the study authors “have declined to respond affirmatively to requests from other researchers for access to the data and analytical methods they used.”

I know that study authors have gone even further – for example, asking that a university department pressure one of their research students to remove social media discussion of the study. Unfortunately, the student did remove his posts – but I can understand the power of institutional pressure.

I think such to such limiting of critical post-publication discussion is ethically unscientific as it inhibits true peer review. It’s made worse in this situation as the journal has a policy of restricting publishing any critiques of papers to four weeks after publication. The journal editor did refer to “the implications of this study” being “debated in the public arena” – but it appears that the authors are not exactly keen on that either.

Large range of problems with the Canadian study

The letter lists a number of problems with the Canadian study. These include:

  1. Focusing on a subgroup analysis amid “noisy data”:
  2. Modeling and variable anomalies:
  3. Lacking data on relevant factors:
  4. Omitting crucial findings:
  5. Using invalid measures to determine individual exposures:
  6. Defining the final study group:
  7. Assessing the impact of fluoride exposure:
  8. Reporting anomalies:
  9. Internal inconsistency of outcomes:
  10. Overlooking research that conflicts with the authors’ conclusions:

I urge readers who are interested in either of these aspects to refer to the letter for details of the problems. The letter includes a list of 30 references relevant to these problems and to criticisms of the study by other professionals.

Scientific politics

In Politics of science – making a silk purse out of a sow’s ear I raised the problems presented by scientific politics where poor studies are often promoted by journals, institutions, and authors. Maybe that is to be expected – science is a human activity and therefore subject to human problems like ambition and self-promotion.

Billboards like this misrepresent the Canadian research. But self-promotion and ambition of researchers and authors provide “authoritative” statements that activists use for such fake advertising.

However, in this case, scientific ambition and self-promotion have led to apparently “authoritative” statements by professionals that have been used to feed the scaremongering of anti-fluoride activists. These professionals may argue they are careful to qualify their statements but in the end, they must bear a lot of responsibility for the sort of completely misleading and false advertising activists have been promoting. Advertising which has serious consequences because of its scaremongering.

Scaremongering and scientific integrity

The letter also raises the problem of scaremongering in its final paragraph:

“. . . the Green article could generate unjustified fear that undermines evidence-based clinical and public health practices. So much is at stake. Hundreds of millions of people around the globe—from Brazil to Australia—live in homes that receive fluoridated drinking water. Hundreds of millions of people use toothpaste or other products with fluoride. Many millions of children receive topical fluoride treatments in clinical or other settings. Tooth decay remains one of the most common chronic diseases for children and teens, and fluoride is a crucial weapon against this disease. Decay prevalence could increase if a journal article unnecessarily frightens people to avoid water, toothpaste or other products fortified with fluoride.”

This letter by 30 high ranking professionals is extremely important. The concerns it raises are very relevant to scientific integrity and hence scientific credibility. I hope that the NIEHS and similar bodies will take on board the responsibility they have to ensure the work they fund is credible, expert, scientifically authentic and as free as possible from personal scientific ambitions and biases.

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Fluoridation – A new fight against scientific misinformation

Anti-fluoride campaigners think a new Canadian fluoride IQ study is the best thing since sliced bread but the scientific critiques warn they are wrong. Photo Illustration by The Daily Beast/Getty

The new Canadian fluoride-IQ study has certainly created some sensational reporting. On the one hand, anti-fluoride campaigners are lauding the study as the best things since sliced bread and seem sure it will lead to the end of community water fluoridation. Mainstream media have featured the findings – although in most cases warn they are controversial and may be meaningless. As would be expected, alternative health media have been promoting it and repeating the anti-fluoridation arguments.

However, scientific commenters have mainly criticised the study and warned that even if the findings are valid it is just one study and it is far too early to consider stopping community water fluoridation – a health policy which is so far been seen as economical, safe and effective in helping fight tooth decay.

I strongly believe the scientific critiques are important. One should not rely on “authority” statements in such matters – especially statements from well known anti-fluoride activists. But we should also be aware that self-promotion by the authors and journal, and by the authors’ institutions, is also not a reliable indicator of the worth of a study.

In the end, the validity and worth of this study will depend on the data and methodology – and good scientific critiques will look at these, not the status of the journal, institutions or authors. And not the public statements being made to promote the findings.

Some interesting critiques are coming from Dr. René F. Najera who is a Doctor of Public Health, an epidemiologist and biostatistician. These are the very skills essential for a proper critique of the Canadian study.

The specific study Dr. Najera refers to is:

Green, R., Lanphear, B., Hornung, R., Flora, D., Martinez-Mier, E. A., Neufeld, R., … Till, C. (2019). Association Between Maternal Fluoride Exposure During Pregnancy and IQ Scores in Offspring in Canada. JAMA Pediatrics, 1–9.

For my other comments on the Candian fluoride/IQ research see:

The “shenanigans” of activists

In his first article, The Hijacking of Fluorine 18.998, Part One, Dr. Najera gives some background. He says:

“Time after time, epidemiological studies have shown that fluoridated water leads to less tooth decay. Less tooth decay leads to better health outcomes as poor oral health is a risk factor for a variety of conditions. At the same time, all of these studies failed to see any association between bad outcomes and fluoridation done correctly.”


” . . those people who were suspicious of putting fluoride in the water did what people who are suspicious of public health interventions often do: they heard of some bad outcome of ingesting fluoride (which is a compound made up of fluorine, the chemical element), amplified it, exaggerated it and showed it as the ultimate example of what fluoride consumption at any concentration can do to a person.”

He compares this to “the shenanigans of the anti-vaccine crowd” and concludes that:

“…just like we had to do in the late 1990s with the Wakefield Fraud “study” that was not a study, here we go fighting a new fight against misinformation…”

He concludes this because:

“In consultation with friends and colleagues, we found a lot to be worried about in the epidemiological design of the study and the biostatistical analysis of the resulting data… And, of course, of the conclusions reached by the authors and the press (with some help from the authors). “

Some epidemiological concerns

In his second article, The Hijacking of Fluorine 18.998, Part Two, Dr. Najera expresses his epidemiological concerns about the research. These include:

1: Unwarranted exclusion of some mother-child pairs:

“For example, some were excluded because they did not drink tap water or lived outside a water treatment zone. Wouldn’t you want to know if not drinking tap water or living outside a water treatment zone led to children with normal-to-high IQs compared to the others?

This raised flags with me because I don’t exclude someone from an outbreak investigation if they don’t have a desired exposure. In fact, I want to know if someone who is not exposed to something is less likely to develop the disease or have the condition I’m studying. It would be like saying that I don’t want women who live in air-conditioned apartments in a city included in a study on Zika because they are not likely to have been exposed to mosquitoes like women living in huts in the jungle.”

2: Overlap of groups:

“In the end, they had 369 mother-child pairs with mean urine fluoride (MUF) measurements, IQ measurements and water fluoride data and 400 mother-child pairs with fluoride intake and IQ measurements. But that’s 769 pairs when 610 children were originally considered? Yes, there is some overlap between the two groups. No big deal if they do their biostats right. (Spoiler alert for Part Three: They didn’t.)”

3: Urinary fluoride data questionable:

“They then used data on mean urine fluoride concentrations from spot (one-time) urine samples taken at different points in the mothers’ pregnancies, and they only accepted those who had been tested throughout (i.e. didn’t miss a test). The problem with this is that the standard to really know how much fluoride someone is exposed to — by testing their urine — is a 24-hour collection of urine. In that test, you have someone collect their urine for 24 hours and then we measure the fluoride (or a lot of other chemicals) in that sample. This is because urine concentrations of chemicals vary throughout the day. If you drink a lot of fluoridated water in the morning, then your urine is likely to have higher concentrations shortly thereafter than in the evening, when you’ve been drinking bottled water without fluoride. Or, if you worked out in the morning and drank energy drinks but stuck to only tap water in the evening, your urine fluoride will be different.”

Other scientific commenters have also been critical of the urinary fluoride data.  Dr F. Perry Wilson suggests that blood plasm fluoride would have been a far better indicator of fluoride intake (see More expert comments on the Canadian fluoride-IQ paper).

The World Health Organisation’s (WHO) recommendations on the monitoring total fluoride intake for populations also stress the need for 24-hour collection and warn that “urinary fluoride excretion is not suitable for predicting fluoride intake for individuals.” [WHO’s emphasis] (see Anti-fluoridation campaigner, Stan Litras, misrepresents WHO).

WHO recommends it only for monitoring fluoride intake of groups of people because of the large effects of individual diets (see Basic Methods for Assessment of Renal Fluoride Excretion in Community Prevention Programmes for Oral Health). But in this Canadian study, urinary fluoride values were used to estimate individual intake of fluoride.

4: Fluoride intake assessed via an unvalidated survey:

“This means that it is hard to know if the survey really measures what it is supposed to measure. Still, they used it, and it leaves the study wide open to recall bias, something you want to minimize as much as possible. And they would have minimized it if they used it a more valid survey, or a prospective design to their study.

First, what is a prospective design? Well, this is when you take a group of women and sign them up for the study, then you carefully measure their fluoride intake with more validated laboratory assays and questionnaires, and then you follow their children and measure their IQ periodically. You don’t do it all retrospectively with already collected data. But, sometimes, what you have is what you have.

Next, what is recall bias? Recall bias is this interesting phenomenon we see when we rely on people telling us their story in order to ascertain risks and outcomes of exposures. We epidemiologists have noticed that people who have bad outcomes tend to be more likely to remember significant exposures. For example, parents of children with birth defects are more likely to remember things like exposures to chemicals or a history of disease in the family. While parents of typical children don’t recall similar exposures as much because, well, they aren’t looking to connect any dots.

(You see this all the time in anti-vaccine circles, where parents of autistic children are more likely to recall bad reactions to vaccines in their children.)”

Dr. Najera also finds this methodology strange because “they multiplied the intake of certain drinks by some factors in order to estimate fluoride intake:”

“This complicates things because, as you saw above, they excluded women who were not in places where the water was being treated and women who didn’t consume tap water. But, come on, have you ever met someone who never consumed tap water? Do we not use tap water to cook foods all the time? What about that fluoride intake? And why just multiply for fluoride in beverages and not, say, that delicious Canadian cheese soup I’ve heard good things about?”

5: Problems with IQ testing of children:

“I’ve asked some friends of mine who are experts in childhood development, and they are skeptical of accurate measurements of IQ in children because children develop at different rates depending on a variety of variables. You may have seen this when you look at a classroom or a school play. Children are on a big spectrum of development, with milestones being really more like average moments.”

6: Sample not representative:

“The sample used in this study is not at all representative of all mothers and their children in Canada, not even close. As we saw in the paper, many women were left out of the study for a variety of reasons, and mother-child pairs were also excluded. I want to believe that there were good reasons for this, but I could not find them in the paper. The authors do mention that they wanted to look only at mothers consuming fluoride, but why not include those who were not expected or outright did not consume fluoride in order to really compare two populations of interest?”

Dr. Najera finishes with a general comment about the way other studies in the scientific literature are used to provide credibility to the findings;

“Finally, the authors mention other studies — some with rats, other purely environmental — where there is some association between fluoride intake and lowered IQ or some sort of negative impact to neurodevelopmental delay. The thing is, public health agencies around the whole world have been looking at these claims and not finding them to be true within their populations. “

I also find the practice concerning, especially as it is relatively common. I think it indicates confirmation bias – the authors making citations that they think support their findings (and purposely refraining from citing studies that don’t). I find this practice disingenuous because it never qualifies the citations with any reference to the applicability to the real-life situation of community water fluoridation. It never points out the high fluoride concentrations used in animal studies or the fact that many research articles on fluoride and child IQ have involved populations in areas of endemic fluorosis where health problems abound.

Dr. Najera is planning a third article discussing the biostatistical issues with the research – a very important issue I have commented on in previous posts. I look forward to it and will do a post on it in due course.

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