
Maternal fluoride exposure during pregnancy and IQ scores in offspring - bookofjoe
https://jamanetwork.com/journals/jamapediatrics/fullarticle/2748634
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merricksb
Separate discussion:

[https://news.ycombinator.com/item?id=20739540](https://news.ycombinator.com/item?id=20739540)

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gamedori
The previous thread was very critical of this article's statistics.

Reposting my comment:

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..

~~~
phreeza
Those multiple comparisons are quite obvious from the text, so a rigorous
reviewer may have asked them to do a Bonferroni correction. Not sure if this
was the case though.

~~~
gamedori
You're right, and one would hope that happened. But not knowing the field or
journal norms, all I could do was search the text for "Bonferroni" and
"regist". In my lab if additional analysis was requested by the reviewer and
we did it, we would have added a sentence to the manuscript.

But not having published in this field or journal, I have no idea what their
norms are.

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colordrops
There is always a lot of skepticism around studies that show fluoridation is
bad for health. Question though, shouldn't we need strong evidence that
_adding_ fluoride to the water is safe, rather than the other way around? Even
if it has some (questionably) positive effects, that doesn't make it right to
add an arbitrary chemical to a fundamental substance needed for life. While we
are at it, why don't we add iodine, vitamin D, magnesium, etc?

~~~
AstralStorm
What kind of safety threshold do you require?

Acute, chronic, cancer studies, Alzheimer's links? Comparison vs bad dental
hygiene in the above? What is the reference group you propose?

How much would you pay for this relatively superb level of detail? (Which is
on par with 50+ years of longitudinal and cross sectional studies. About 1
billion USD.)

~~~
vixen99
No need to pay a cent if you don't add it to the water. Anecdotally it appears
difficult to find a toothpaste than doesn't contain fluoride sufficient to
strengthen tooth enamel & bone via its incorporation over time and there are
other sources in food and drink (tea). Fluoride has no other role in human
metabolism.

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coding123
If you're water conscious like me that doesn't want anything "added" to the
water, consider buying a home distiller. Just search for distiller in amazon
for some ideas of what you get. It takes 3-5 hours for about a gallon. If you
just queue them up during your work day. Just store the water in large glass
mason jars and throw them in the fridge. Kick the plastic bottled water
habits. It's not just BPA but tons of plasticizers that leech into your fav.
bottled waters. My wife and I switched to this after we drank some Fiji from a
gas station, after it had warmed up - all you can taste is plastic - even with
the BPA free stickers. In the end we decided you can't really trust the
companies distributing plastic bottled water because you never know which
crate is left out in 105 degree summer heat during its various transitions.
That's pretty disgusting if you think about it.

~~~
basicplus2
If you do go down this track you need to re-mineralise the water as pure water
is damaging to the body as pure water will leach all the electrolytes from
your body.

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phyzome
Not if you're also eating food.

~~~
whenchamenia
Most people are already deficient in salt and magnesium, I think more is
likely better.

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tdonovic
All the tap water in Australia is fluoridated. You would be considered a bit
odd if you drink filtered water instead of tap water (bar say SA where the
water tastes bad). All other things equal, we should expect 3&4 yearolds to
have a 3.66 higher IQ than those, say, in NSW, where the water is treated and
tastes good enough to drink?

Surely there are some population effects or something else going on here, or
the effect, especially later on in life, evens out between the groups.

~~~
aplummer
Particularly with the nationwide school test scoring, there should be
statistically significant score differences in QLD (only recently
fluoridated).

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mindfulhack
[https://www.sciencemag.org/news/2019/08/drinking-
fluoridated...](https://www.sciencemag.org/news/2019/08/drinking-fluoridated-
water-during-pregnancy-may-lower-iq-sons-controversial-study-says):

 _" If the work holds up—a big “if,” as the paper’s findings are already
coming under heavy scrutiny—it could hold serious implications for public
policy."_

Why should scientific data be doubted simply because its implications, if
taken seriously, would be to cause more inconvenience or less money-making in
our lives?

~~~
Arbalest
Because it would be too easy to influence public policy by any interested
parties. We already know corporations sponsor papers for their PR, this just
means it would become a simple tool to influence policy.

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tomq
Barely significant results like this are suspect. See
[https://www.vox.com/science-and-
health/2017/7/31/16021654/p-...](https://www.vox.com/science-and-
health/2017/7/31/16021654/p-values-statistical-significance-redefine-0005) for
a good overview. TLDR: the smart money is on this result failing to reproduce.

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ve55
Reposting a more skeptical comment to provide some balanced responses:
[https://old.reddit.com/r/slatestarcodex/comments/cslscx/is_f...](https://old.reddit.com/r/slatestarcodex/comments/cslscx/is_fluoride_potentially_neurotoxic/exfkypd/)

>Sci-Hub Link: [https://sci-
hub.se/10.1001/jamapediatrics.2019.1728](https://sci-
hub.se/10.1001/jamapediatrics.2019.1728)

>Study itself: [https://sci-
hub.se/10.1001/jamapediatrics.2019.1729](https://sci-
hub.se/10.1001/jamapediatrics.2019.1729)

>A decent amount of this is focused on Black Tea consumption during pregnancy
which is apparently a problem:
[https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4808922/](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4808922/)

>Collected skeptical commentary at the Science Media Centre:
[https://www.sciencemediacentre.org/expert-reaction-to-
study-...](https://www.sciencemediacentre.org/expert-reaction-to-study-
looking-at-maternal-exposure-to-fluoride-and-iq-in-children/)

>First, the claim that maternal fluoride exposure is associated with a
decrease in IQ of children is false. This finding was non-significant (but not
reported in the abstract). They did observe a decrease for male children and a
slight increase in IQ (but non-significant) for girls. This is an example of
subgroup analysis – which is frowned upon in these kinds of studies because it
is nearly always possible to identify some subgroup which shows an effect if
the data are noisy. Here the data are very noisy. A further issue is that the
estimate of the decrease in IQ for male offspring is unfeasibility large – at
4-5 IQ points. This level of average deficit would be readily detectable in
previous studies and is likely a reflection of bias or very noisy data (the
interval estimate here is very wide). As high fluoride areas are not randomly
assigned there are also countless uncontrolled confounders. While they did
correct for a limited set of covariates, the overall effect was non-
significant with and without covariates. In summary it is not correct to imply
that the data here show evidence of a link between maternal fluoride exposure
and IQ. The average change in IQ is not statistically significant.

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BIair
_Estimated Fluoride Intake and IQ A 1-mg increase in fluoride intake was
associated with a 3.66 (95% CI, −7.16 to −0.15; P = .04) lower FSIQ score
among boys and girls_

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broski-billups
I'm on Detroit water and just checked the latest water test I could find --
.57ppm fluoride. If I did the math right, there is 1mg fluoride in every .46
gallons of water.

~~~
broski-billups
Additionally, the maximum level allowed in my city is 16mg per gallon, and has
been since I was born. However, in the year I was born(1992) the maximum
measured level per the city test was 48mg per gallon.

