Drinking fluoridated water during pregnancy may lower IQ in sons | Hacker News Reader

Drinking fluoridated water during pregnancy may lower IQ in sons

sciencemag.org

88 pointstshannon77 comments

Here's the meat:

> About 40% of the nearly 600 women lived in cities with fluoridated drinking water [...]. Three to 4 years after the women gave birth, researchers gave their children an age-appropriate IQ test. After controlling for variables such as parental education level, birth weight, prenatal alcohol consumption, and household income, as well as exposure to environmental toxicants such as lead, mercury, and arsenic, they found that if a mother’s urinary fluoride levels increased by 1 milligram per liter, her son’s (but not her daughter’s) IQ score dropped by about 4.5 points. That effect is on par with the other recent studies looking at childhood IQ and low-level lead exposure.

So that's an average 1.3 IQ drop in cities with fluoride. For 1 gender. In an IQ test for 4 year olds. An IQ test.

Can anyone with more knowledge of statistics chime in? This feels like it cannot be statistically significant with n=600, a subgroup analysis and a test I cannot imagine being even remotely accurate (IQ test for 4 year olds)

Until another replicated study comes along to dispute this, I'll take the word of the author and the editors at JAMA over your 'feel' that this isn't statistically significant.

"There was a significant interaction (P = .02) between child sex and MUFSG (6.89; 95% CI, 0.96-12.82) indicating a differential association between boys and girls. 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)."

1. https://jamanetwork.com/journals/jamapediatrics/fullarticle/...

I browsed the article and have a basic understanding of statistics, no need to get patronizing.

The article does not state the variance of this IQ test and does not state how many subgroups they analyzed and whether they corrected for that or if they a-priory were planning on analyzing gender.

Picking subgroups until you've found one that is statistically significant is a well known technique in P-hacking.

Other problems:

- The IQ score for girls is 5 points higher on average than for boys in the study group

- Fluoridation has the opposite effect for girls, the average IQ was 1.5 points higher. It is really strange for a chemical to have a completely different effect on young girls and boys. Statistical variance is much more likely

- The average IQ score in the sample was 107, well above the average 100

- Parent IQ was not a variable, only the very roughly correlated high school diploma or not and household income.

"Extraordinary claim require extraordinary evidence", and this study seems to at best be an indication that further research is needed rather than iron-clad proof of this effect.

It's really not that strange for a chemical to have different effects on girls and boys, anything that affects sex hormones at all or sex-specific development is going to have a different effect.

Even in 4 year olds, though? And such that it produces the exact opposite effect compared to the control?

Kinda looks like p-hacking. They ran calculated the p-value for a bunch of different criteria until they found one that was "statistically significant" (in this case gender, specifically just one gender). The issue is that you'll find 5% outliers 5% of the time, so if you just keep looking you'll eventually find "significance".

This would demand reproduction before action.

It only looks like p-hacking if you go in with the belief that the results can not possibly be correct, and even then Hanlon's Razor would make me reluctant to accuse them of p-hacking.

If an effect only occurs in a subgroup which we have no explanation for, it's a smell that different subgroups were tried until a "statistically significant" one was found by chance.

Why is someone raising the question of p-hacking and suggesting a replicated study is needed being downvoted?? The paper is described as “barely statistically significant” so p-hacking, which on HN we see is rampant, seems like it should be discussed

Regardless of whether it's statistically significant in terms of p-value, its pretty hard to discount the possibility the controls might not be effectively applied (and I find the basic idea that fluoride might have adverse developmental affects on babies highly plausible). When you're comparing fluoridated and non-fluoridated areas of just six cities there are likely to be other regional effects not perfectly captured by the controls - whilst controlling for parental education they found systematic differences in the parents' education levels between fluoridated and non-fluoridated communities. And they attempted that controlling without any data for the most significant factor in child IQ - parental IQ...

“Despite that, several researchers argue that the paper’s methodological shortcomings undercut its importance. In a statement to the Science Media Centre in London, an independent organization that sources expert opinions on science in the news, psychologist Thom Baguley of Nottingham Trent University in the United Kingdom noted the data “are very noisy,” meaning they contain a lot of other factors that could easily lead to false positives. Psychologist Stuart Ritchie at King’s College London added that the findings are just barely statistically significant, calling them “pretty weak and borderline.” By itself, the study “shouldn’t move the needle much at all on the question of the safety of fluoride,” he wrote.”

Safe treatment? Great.

How about obtaining informed consent first?

When I see a headline like this my instinct is to jump to "overfitting".

In a study like this they use P=0.05 as their cut off for significance. One in 20 such studies would be expected to give meaningless results. But they had the choice of cohort (all kids or boys and girls separately), so 1 in 10. They measured urine concentrations of fluorine at three time points during pregnancy, which makes for 7 different potential combinations of input variables, for a total of 14 different potential analyses, where 1 in 20 is expected to be significant. Of course, they didn't preregister, so who knows whether their analysis changed on the fly..

Good points. It's even more than 1 in 20 when you realize that studies does no get published with p > 0.05, so in the "published studies" sample this effect should be even larger.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4418502/ This article from 2014 classifies fluoride as a neurotoxicant.

Why is a link to peer reviewed material getting downvoted ?

Not liking the study is one thing but downvoting a link to material without stating a reason is willful ignorance.

It's absolutely dangerous in large quantities, like most anything else is dangerous in large quantities.

I am not a scientist and anyone who is should feel free but from what I have read flouride is a bioaccumlator.

At what point does it become dangerous to continue to drink water ?

Drowning is a strong contraindicator.

There is also water intoxication, which can be deadly.

From flouride was assumed... humor noted ;)

> At what point does it become dangerous to continue to drink water ?

According to this page [0], the LD50 of water is 6 liters, so somewhere before that.

[0] https://www.compoundchem.com/2014/07/27/lethaldoses/

> I have read flouride is a bioaccumlator

Well, that's something I never heard about, and contradicts even basic high-school chemistry.

Where did you read it?

various places on the net.. some sites are crackpot but others seem ok... I will let you decide which category this falls in

https://www.atsdr.cdc.gov/phs/phs.asp?id=210&tid=38

There is nothing about bioaccumulation there.

Fluoride is one of those ions that diffuse thought and out of our bodies almost like there is no barrier anywhere.

Animals that eat fluoride-containing plants may accumulate fluoride. However, the fluoride accumulates primarily in the bones or shell rather than in edible meat.

The reference the author uses to support his claim in this case referred to a review he co-authored that looked at high concentrations of fluoride. Her is one funded by the National Toxicology Program both relevant to community water fluoridation concentration levels of fluoride (low): https://link.springer.com/article/10.1007/s12640-018-9870-x#... - which found, for male Long-Evans Hooded Rats at least, " Drinking water exposure at these low levels was not found to alter motor performance or learning and memory in the test paradigms assessed. Low-level F− did not alter thyroid hormone levels and produce neuronal damage or glia reactivity in the hippocampus, or histological damage in the heart, kidney, or liver. The low-level F− diet did not show a significant effect on the behavioral endpoints examined."

I predict this research will receive reasoned and appropriate appraisal by the press and public officials.

Or, ya know, the real experts.....parents on Facebook.

Well, you can do what you like but when it comes to complex medical issues my winning strategy is to wait for a Hollywood actor, famous musician, or a daytime TV host to tell me what to think.

Original study without the opinionated article:

https://jamanetwork.com/journals/jamapediatrics/fullarticle/...

Going forward, it'd probably be appropriate to only post the studies and not some sleazy clickbait opinion headline "you won't believe what this controversial study says blah blah!"

This will definitely need further testing to confirm validity and to pin down the effect further, but if true, that will leave the question of whether as a society we feel the substantial dental health benefits in most areas are worth the 1.3-point IQ reduction, and if not, what we can do to counterbalance the effects of removing flouride from the water.

Edit: Corrected the IQ drop amount.

The average IQ drop was 1.3 points. It's 4.5 points per mg/L of fluoride and the average difference was 0.29 mg/L.

> Longtime fluoridation critics are lauding the study, but other researchers say it suffers from numerous flaws that undercut its credibility. Either way, “It’s a potential bombshell,” …

Umm, what?

What, you missed Jack Ripper's celebratory tweetstorm?

Did he suggest that women drink only pure-grain alcohol during pregnancy?

Is IQ even a significant measure? What a drop of 1.3 points in average even means. There is a measurable, real difference between a 120 and a 121.3 IQ person? This smells p-hacking

No. It has been demonstrated on numerous occasions that all IQ tests are ineffective in predicting long term outcomes along any measure.

It’s also been demonstrated in numerous studies that IQ tests are not remotely objective - cultural and other variations produce massive gaps in measured IQ of individuals in different social groups. To the extent that you can engineer IQ tests “without bias” that demonstrate group A is smarter than group B, for almost any groups A and B.

That’s before we get into the borderline statistics, weak methodology, and vanishingly small sample size: 600 infants, so somewhere in the realm of 300/300 split, so they’re saying a p=0.05 result of a 1.3 point drop in IQ. You only need a minor number of infants with learning difficulties to cause that. Even if the testing methodology were sound (which it isn’t).

Addendum:

Per [1] the prevalence of learning disabilities is 7.8% of the population of 3-17 year olds, with 3.8% showing severe learning impairment. So if we take our 600 infants we’d expect around 40 kids with learning difficulties to some extent. But it should be easy to see that at the relatively tiny sample sizes (generously 150 boys in the F vs non-F groups) that minor variance would be more than sufficient to skew things.

Further sample considerations: controlling for all those variables necessarily increases the noise (legit not sure how they get to p=0.05) due to the further reduced group sizes.

[1] https://www.ncbi.nlm.nih.gov/books/NBK332880/

Is it just me or do the groups have a significant overlap in their margin of error?

Returning to this, I did the calculations and here is the margin of error for each group: 11%, 9%, 9%. Their common error (the overlapping region of area) is the interval 87.79-104.95. The IQ scores from each group (94.91, 96.29, 96.47) are well within that margin of error. If you perform a t-test on 3-Ca vs. 3-placibo you'll see that the difference is not statistically significant.

How is this study concluding these results? What math are they using?

From the research article:

> 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).

> A 1-mg higher daily intake of fluoride among pregnant women was associated with a 3.66 lower IQ score (95% CI, −7.16 to −0.14) in boys and girls.

I'm not sure about the notation, but even the first result looks pretty close to include the null hypothesis, where the change is 0.

It's interesting how policies like fluoridation of water are accepted at face value assuming the highest of scientific / statistical rigor was used to justify them. Of course that is not the case. Yet it requires just that, not common sense, to even question the practice in a manner that people will not consider somehow off-kilter. Our faith in authorities is stronger than ever, while the scientific community struggles with our basic ability to reproduce much of the research we even today cite is rigorous even ground-breaking.

Interesting you get downvoted for stating we should question everything to include authority.

Thought science was all about questioning and reconfirming truth as more knowledge is obtained

I think that we are in for a new renaissance of scientific discovery as we grapple with all of the issues related to the reproducibility crisis. It will lead to better statistics, better science and more useful results. Untill then we will have people arguing with the authority of their position and "because science"

If you took a look at the study and the margin of error for their results, you'd notice that the margin of error has an overwhelming overlap.

I'm not against fluoridation, but it does seem weird that we're so certain about these things...until we're not.

Shouldn't we stop doing one-size-fits-all medication and actually expand access to toothpaste & dentists?

There are drugs that help with specific complications that are just simply not made because the market for them is too small, they're call orphan drugs (https://en.wikipedia.org/wiki/Orphan_drug). The drugs that make it to market are not necessarily the best at treating you, they just cover enough of the population (normally more than one ailment per drug) and can be profitable.

I understand these. And it pains me that they exist.

I'm mostly talking about the availability of certain medication. Like, it makes sense to have a nationwide vaccine program. It doesn't make sense to have fluoridated water due to the relative ease of access to toothpaste.

Especially because we really can't tell with certainty what consuming this does in the long-multigenerational term. Why should we take the risk?

In my youth I lived off a well and did not have access to fluoridated water. My parents still live in that house. There are large swaths of people who live off of a well in the United States. We started adding fluoride to water because our knowledge at the time said it was a good idea (and still probably is). The rates of tooth decay falls when fluoride is introduced in drinking water.

https://www.cdc.gov/fluoridation/pdf/natures_way.pdf

But the only places that have fluoride added to the water are metropolitan areas (at least around me in a Midwestern state).

The weakness of this argument is that there has been no control for a rise in rates of disease over many decades it would take for a bio-accumulating substance.

I understand - fluoridation has been immensely helpful. However, should we re-visit our decisions every once in a while and see if we can do things differently?

Toothpaste production is now more streamlined. We know the immense benefits of fluoride, so getting it to people in a more concentrated and localized matter can be a next step in helping people with this.

Essentially I'm saying it was a potential risk we accepted because the benefits far outweighed the potential risk down the line, but now that we have alternative solutions with smaller potential risk should we discuss them or not?

The effect of fluoride is in addition to the effect of toothpaste and other fluoride delivery modalities (25%). Even if that were not the case, prior to the adoption of other fluoridation modalities, fluoridation reduced cavities by as much as 65%. Additionally, for urban centers it costs less than a tube of toothpaste per person per year. Finally, it works without requiring a behavioral intervention - people naturally drink and eat. It is not considered one of the top ten public health interventions of the 20th century for nothing.

If this turns out to be true, I hope they'll take a closer look at the relationship between Fluorine and Iodine. My guess is the fluorine has effects that mimic iodine deficiency and perhaps increasing iodine can counter the negative effects of the fluorine. Women also need more Iodine than men, though I'm not sure if that's true at age 4 but it might explain the sex difference as well.

It's a nice idea, but I think it's wrong.

The nice part is that Fluorine and Iodine are in the same column of the periodic table, so they are somewhat similar.

The problems is that between Fluorine and Iodine there is Chlorine and Bromine. Let's ignore Bromine for simplicity.

The recommended intake of Fluorine and Iodine is approximately .001 or .002 g/day, and the recommended intake of Chlorine is 1 or 2 g/day. (With a lot of simplifications. For a serious number ask your medical doctor.)

So the intake of Chlorine is almost 1000 bigger than the intake of Fluorine and Iodine. So my guess is that the problem in whatever part of the body that need to recognizes Iodine is that there is too much Chlorine. Also Chlorine is more similar to Iodine.

Here's an interesting aspect to the source of flouride of which most people are unaware:

https://origins.osu.edu/article/toxic-treatment-fluorides-tr...

Here is the CDC take on the products used in fluoridation. https://www.cdc.gov/fluoridation/engineering/wfadditives.htm... They are all subject to NSF Standard 60 requirements for purity. "Some have suggested that pharmaceutical grade fluoride additives should be used for water fluoridation. Pharmaceutical grading standards used in formulating prescription drugs are not appropriate for water fluoridation additives. If applied, those standards could actually exceed the amount of impurities allowed by AWWA and NSF/ANSI in drinking water."

Does it set a cap in potential or just drop in each individual relatively?

Did this come from the John Birch Society?

The conspiracy theorists were right?

Old news.

People have suspected for a while, but it was not as clear as this new larger study. This is much more difficult to dismiss.

If the math was solid, you'd have a point. But it doesn't, so you don't.

Because you know more then the editors at Jama? Without explaining why?

Returning to the math, I did the calculations and here is the margin of error for each group: 11%, 9%, 9%. Their common error (the overlapping region of area) is the interval 87.79-104.95. The IQ scores from each group (94.91, 96.29, 96.47) are well within that margin of error. If you perform a t-test on 3-Ca vs. 3-placibo you'll see that the difference is not statistically significant.

I'm sorry but if you've done even the most minimal study of fluoride levels, this is something you'd know - not because it's proven but because the extrapolated data going back from decades makes sense.

To the point - the movie Doctor Strangelove even goes as far as to mock this controversy. So, I restate my claim. If you know nothing of this, then it's because you haven't researched it.

How do fluoride levels alone prove anything? Also fluoride levels of (or in) what? You make vague claims that you think are to support some point that is not clear.

Drinking fluoridated water does not do anything to protect teeth. They don't have it in Europe and have dental health that's just fine. Just goes to show you can do ANYTHING with good PR. The Fluoridation campaign was headed up by Edward Bernays[1] who was Freud's Nephew and one of the greatest propagandists of all time. His other famous accomplishment was convincing women that they should smoke[2].

[1] https://en.wikipedia.org/wiki/Public_relations_campaigns_of_...

[2] https://en.wikipedia.org/wiki/Public_relations_campaigns_of_...

I'm no fan of mass medication without a choice (or supplementation, whatever), but what you state is not the full story:

> They don't have it in Europe and have dental health that's just fine.

Much of Europe (not all) doesn't fluoridate their water, but they DO fluoridate salt and milk, or have high levels of natural fluoride in their water.

To quote wikipedia[1] (yes, yes, I know, although they at least have a citation[2] for it):

> the European Commission finds no advantage to water fluoridation compared with topical use

> Community water fluoridation is rare in Continental Europe with 97–98% choosing not to fluoridate drinking water. Fluoridated salt and milk is promoted in some European countries instead. Water fluoridation has been replaced by other modes in many countries where water supplies are too decentralized for it to be a practical choice, or existing natural fluoride levels were already ample, including Germany, Finland, Japan, Netherlands, Sweden, Switzerland, Denmark and at a time Israel.

That doesn't mean they didn't find fluoridation useful, just that topical use is just as good.

Personally, I dislike the idea of forcing everyone to use fluoridated products (by not providing alternatives, or by putting it in all the water) and would prefer if topical use were encouraged instead, but my preferences aside, fluoride has been proven to be beneficial to teeth.

[1] https://en.wikipedia.org/wiki/Fluoridation_by_country

[2] https://en.wikipedia.org/wiki/Fluoridation_by_country#cite_n...

Being effective is not the same as being safe. Has it been disproven to cause any number of potential long term ill effects? Just two of which are suggested connections to weakening of bones and cognitive impairment / alzheimer's. This is the old debate over the precautionary principle I suppose, but it bolsters the argument for personal discretion rather than heavy handed imposition of "treatment."

I'm not arguing that either way, I'm just pointing out that the often repeated mantra of "Europe has banned fluoridated water" or the many variants of that which I keep hearing are not exactly correct.

When I lived in Europe, I always drank bottled mineral water.

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