Just imagine it. If the local anti-fluoride group Fluoride Free NZ (FFNZ) really put their faith in “Top Medical Journals” they would now be erecting billboards encouraging pregnant women to drink fluoridated water because a new study shows a positive relation of child cognitive abilities with prenatal maternal urinary fluoride.
The study has been reported at a recent conference – this is the citation and links to an abstract:
Santa-Marina, L., Jimenez-Zabala, A., Molinuevo, A., Lopez-Espinosa, M., Villanueva, C., Riano, I., … Ibarluzea, J. (2019). Fluorinated water consumption in pregnancy and neuropsychological development of children at 14 months and 4 years of age. Environmental Epidemiology, 3.
This appears to be research using Spanish data and the abstract reports that a number of cognitive measures for children aged 4 – 5 years-old are positively related to their mother’s prenatal urine fluoride concentrations:
“At the age of 4-5 years, an increase of 1 mg/l in the level of fluoride in urine during pregnancy (mean level of 1st and 3rd trimesters) was related to a higher score on the perceptual-manipulative scale of 4.44 (0.13, 0.75) points. Taking into account the window of prenatal exposure, at week 32 the level of fluorine was associated with an increase of 4.11 (0.28, 7.94) points in verbal function, 3.57 (-0.03, 7.18) in perceptive-manipulative and 3.97 (0.29, 7.65) in general cognitive.”
And the researchers concluded:
“Prenatal exposure at the levels found in fluorinated drinking water may exert a beneficial effect on the development at 4 years of age. At low doses, fluoride could present a dose-response pattern with a beneficial effect.”
Compare this with the report of a negative effect taken from the abstract of Green et al., (2019) – the study FFNZ relies on for their current scaremongering propaganda:
“A 1-mg/L increase in MUFSG was associated with a 4.49-point lower IQ score (95%CI, −8.38 to −0.60) in boys, but there was no statistically significant association with IQ scores in girls (B = 2.40; 95%CI, −2.53 to 7.33).” [MUFSG is an abbreviation for maternal urinary F cocnetration].
And Green et al., (2019) concluded:
“In this study, maternal exposure to higher levels of fluoride during pregnancy was associated with lower IQ scores in children aged 3 to 4 years. These findings indicate the possible need to reduce fluoride intake during pregnancy.”
So there you go. You can happily erect a billboard to promote either message depending on your own bias and your desire to confirm that bias. You can scaremonger and attempt to frighten mothers and pregnant women. Or you can do the opposite – perhaps even scaremongering to warn mothers that they must drink fluoridated water – or warn them not be taken in by activists who only wish to reduce your child’s opportunities in later life.
My take on this.
I have yet to see the full paper reporting this study and look forward to its publication. But I am not looking to confirm a bias – I simply want to see the data and subject it to the same sort of scientific critique I have made for the Green et al (2019) paper.
My initial response is that the reported relationship will be weak (going on the confidence intervals given). So I am sure that many of the criticisms I made of Green et al., (2019) will also apply to Santa-Marina et al., (2019).
But I think this situation with conflicting results from different research groups – both relying on weak statistical relationships – is the sort of result we can expect from analysis of unsatisfactory weak data. Sensible readers should be aware of this and not be swayed by single studies – especially studies using very weak relationships.
Unfortunately, activists do not have such scientific ethics – they will simply use the data and studies supporting their propaganda and biases. And they will claim these studies are of high quality and the best thing since sliced bread. On the other hand, these activists will attempt very hard to discredit the new study and I wonder if they will be able to see the irony of using arguments that could equally be used against the Green et al., (2108) study they promote.
More serious is the confirmation bias that goes on in the scientific community and the way authors like those involved in the Green et al., (2019) paper make statements promoting their work which are then used by activists to promote scaremongering messages.
I do not know enough about the research group involved in the Santa-Marina et al., (2019) study but, from their record, the other research group headed by Christine Till seem to be driven to confirm their bias against community water fluoridation and this is motivating them to extract weak relationship from poor data.
See my critiques of papers from Christine Till’s group:
- ADHD linked to elevation not fluoridation
- ADHD link to fluoridation claim undermined again
- Fluoridation not associated with ADHD – a myth put to rest
- Fluoridation and attention deficit hyperactivity disorder – a critique of Malin and Till (2015)
- ADHD and fluoride – wishful thinking supported by statistical manipulation?
- What do these mother-child studies really say about fluoridation?
- Biostatistical problems with the Canadian fluoride/IQ study
- Fluoridation – A new fight against scientific misinformation
- Politics of science – making a silk purse out of a sow’s ear
- If at first you don’t succeed . . . statistical manipulation might help
- Fluoridation and ADHD: A new round of statistical straw clutching
I hope that this new study is reported in the media with the same interest the Green et al., (2109) study was. But I also hope the situation is used to get the message across that this sort of study should not be used to inform public policy. And that we should not be taken in by the scaremongering promotion of these sort of weak studies by anti-fluoride activists.