Tag Archives: hypothyroidism

Anti-fluoride activists misrepresent another thyroid study

Image credit: Hypothyroidism | Natural Approach To Low Thyroid Hormone

Anti-fluoride activists closely follow the publication of results from fluoride studies and react to new scientific papers in one of the following ways:

  1. Use it to claim community water fluoridation (CWF) is harmful – even if this requires misrepresentation or distortion of the studies findings (a recent example is the prenatal fluoride/child IQ study of Bashash et al., (2017)  heavily promoted and misrepresented by Paul Connett in his current New Zealand talks).
  2. Viciously attack the study if it finds CWF beneficial and reports no harmful effects (remember their reaction to the NZ IQ-Fluoridation study of Broadbent et al., 2014).
  3. Do their best to ignore the study if it can’t be misrepresented and the media is not reporting it.

Well, now we have a very new study from Iran reporting relationships between drinking water fluoride and thyroid problems and already we can see activists launching into reaction 1.

The paper is:

Kheradpisheh, Z., Mirzaei, M., Mahvi, A. H., Mokhtari, M., Azizi, R., Fallahzadeh, H., & Ehrampoush, M. H. (2018). Impact of Drinking Water Fluoride on Human Thyroid Hormones: A Case-Control Study. Scientific Reports, 8(1), 2674.

So what did this study find? The paper itself is a little difficult to read but here is what I got from it.

No effect of drinking water fluoride on hypothyroidism

The study investigated two groups (“cases” – which had hypothyroidism and “controls” – which did not have hypothyroidism) and two drinking water fluoride concentration ranges ( 0 – 0.29 mg/L and 0.3 – 0.5 mg/L). To quote the findings:

“The frequency distribution of hypothyroidism based on the different levels of fluoride in drinking water was not significant for the cases (P = 0.13) and controls (P = 0.21) in YGA.”

And:

“At a concentration of below 0.5 mg/L, however, it [fluoride] is not an important factor for hypothyroidism in YGA.”

YGA is the “Yazd Greater Area . . . located in the Yazd province of Iran, which uses groundwater as the primary water source.”

So, no association found between hypothyroidism and drinking water fluoride. Yet, the Irish anti-fluoride guru, Declan Waugh, reported on Facebook

“the current study Published in Nature this past week, found that fluoride in drinking water, at levels below those present in tap water in Ireland, may contribute to thyroid impairment and a worsening of thyroid conditions in adults. In other words fluoride can contributed to sub-clinical and clinical hypothyroidism”

To avoid confusion, Waugh is referring to this study. Scientific Reports is a Nature journal.

So Waugh is citing a study which reported no statistically significant effect of fluoride concentration on the prevalence of hypothyroidism to claim “that fluoride in drinking water, at levels below those present in tap water in Ireland, may contribute to thyroid impairment and a worsening of thyroid conditions in adults!”

Incidentally, I do try to follow anti-fluoride activists on social media but did not see this myself as Declan Waugh blocks me. This was brought to my attention by a colleague who was probably more concerned about Waugh’s resorting to blaming homosexuality on fluoride – see the image of Waugh’s Facebook post. Citation dredging of the sort Waugh indulges in certainly makes one susceptible to these sort of claims – especially if they “confirm” a bias.

The study is already being used by groups like UK Against Fluoridation and Fluoride Free NZ who cite the paper as evidence of harm – but seem not to understand the paper and simply quote sections dealing with thyroid hormones and not the findings on the lack of effects on hypothyroidism prevalence.

Thyroid hormones

The study did report statistically significant differences in hormone levels.

I am not an endocrinologist so will not get into a discussion of what these changes might mean. Here I will simply present them and compare them with hormone levels considered normal.

The authors investigated the T4, T3 and TSH hormones.

No significant fluoride effects occurred with the T4 hormone.

A very small effect occurred for the T3 levels in the control group (no hypothyroidism present) – the authors claimed this was statistically significant but I find that hard to believe – see Figure.

The T3 hormone levels were within the normal range (yellow area) for both groups. It’s not surprising to see different levels in the hypothyroidism cases. But drinking water fluoride has no significant effect there (p=0.19) – and I am picking the claim of a statistically significant effect (p=0.026) on the control group is wrong.

The authors claimed significant differences of TSH hormone with fluoride concentration for both the control and hypothyroidism groups – see Figure.

The TSH levels for the control group was in the normal range (yellow area) and the difference (although statistically significant, p=0.001) was extremely small. The levels for the hypothyroidism cases were outside the normal range – probably as a result of hypothyroidism. Again, I wonder at the claimed statistically significant effect (p=0.003) of fluoride for the hypothyroidism cases.

Other risk-modifying factors

While hypothyroidism prevalence was not significantly related to fluoride concentration the study reported that it was related to gender, family history of thyroid disease, water consumption, exercise, diabetes, and hypertension.

The authors note that “patients with hypothyroidism . . .  have a higher consumption of drinking water.” So this association probably means increased water consumption is a result of hypothyroidism and not a cause of it.

Some misleading comments in  the paper

The authors seem to have an anti-fluoride bias, and I wonder at studies which demonstrate statistically significant relationship for a range of risk-modifying facts, but not for fluoride, yet still concentrate on possible fluoride effects. Particularly at such low fluoride concentrations.

For example, the authors say:

“we obtained an unadjusted OR of about 1.034 (CI 95%: 0.7–1.53) for fluoride in drinking water when its concentration was less than the standard (0.2–0.5 mg/L). This finding is consistent with the Peckham study in England, which reported OR = 1.5 (CI 95%: 1.16–2) for hypothyroidism, where the maximum fluoride concentration was more than 0.7 mg/L.”

That is just special pleading – trying to “save” a non-significant result. And special pleading to compare it with the Peckham study which has been roundly criticised for not considering the effects of iodine deficiency which is known to be a major contributor to hypothyroidism.

And another case of special pleading is this:

“TSH values are higher (in both cases and controls) with higher levels of water consumption. This is consistent with an association between increased fluoride intake (due to increased water consumption) and increased TSH.”

They have turned this water consumption on its head – now ignoring that it is caused by hypothyroidism (patients drink more water) and claiming the TSH changes are a result of increased fluoride intake. This is simply an attempt to overcome the lack of any statistically significant effect due to fluoride levels in drinking water by postulating there is really an effect because of increased water consumption by hypothyroidism patients.

Conclusion

I do not think this is a good paper. Decent peer review could have improved it – and hopefully removed the obvious bias and special pleading of the authors.
It cannot honestly be used to claim fluoridation causes hypothyroidism – as anti-fluoride campaigners will do. However, activists will dredge out quotes from this paper which will be used to give an impression of results actually not present in the paper (fluoridation causing hypothyroidism).

So a paper which actually doesn’t support anti-fluoride claims – but can easily be misrepresented to fool the uncritical reader.

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Anti-fluoridation campaigners often use statistical significance to confirm bias

I was pleased to read this Nature article – Five ways to fix statistics – recently as it mirrors my concern at the way statistical analysis is sometimes used to justify or confirm a bias and not reveal a real causal relationship. Frankly these days I just get turned off by media reports of studies showing statistically significant relationships as evidence for or against the latest health or other fads.

As the Nature article says, statistical significance tests often amount “to uncertainty laundering:”

“Any study, no matter how poorly designed and conducted, can lead to statistical significance and thus a declaration of truth or falsity. NHST [null hypothesis significance testing] was supposed to protect researchers from over-interpreting noisy data. Now it has the opposite effect.”

No matter how good a relationship appears, or how significant the statistical analysis shows it to be, it is simply a relationship and may have no mechanistic or causal backing.  An example often used to illustrate this is the close relationship between the prevalence of autism and sales of organic produce.

Clearly statically significant but we don’t find those activists claiming autism is related to one thing or another ever citing this one. I am picking these activists may well have a bias towards organic produce.

Here are several examples I have discussed before which illustrates how “statistical significance” is sometimes used to confirm bias in fluoridation studies. I think these are very relevant as anti-fluoridation campaigners often cite statistical significance as if it is the final proof for their claims.

Ignoring relevant confounders

This is an easy trap for the biased researcher (and let’s face it, most of us are biased – it’s only human). Just ignore other confounders or risk-modifying factors that may be more important. Or ignore the fact that the risk-modifying factor one is interested in (in this case fluoride) may just be acting as a proxy for (and therefore is related to) something else which is more relevant.

This why all credible risk-modifying factors should be considered in correlation studies. They should be included in the statistical analyses.

It’s amazing how many researchers either ignore the possible risk-modifying factors besides their pet one – or pay lip-service to the problem by limiting their consideration to only a small range of such factors.

Examples of studies promoted by anti-fluoride campaigners where this is a problem include:

Peckham et al., (2015) hypothyroidism paper:

Peckham, S., Lowery, D., & Spencer, S. (2015). Are fluoride levels in drinking water associated with hypothyroidism prevalence in England? A large observational study of GP practice data and fluoride levels in drinking water. J Epidemiol Community Health, 1–6.

This has been widely condemned for a number of reasons – one of which is that iodine deficiency, a known factor in hypothyroidism, was not included in the statistical analysis.

(See Paper claiming water fluoridation linked to hypothyroidism slammed by experts and Anti-fluoride hypothyroidism paper slammed yet again).

The  Takahashi et al., (2001) cancer paper:

Takahashi, K., Akiniwa, K., & Narita, K. (2001). Regression Analysis of Cancer Rates and Water Fluoride in the USA based Incidence on IACR / IARC ( WHO ) Data ( 1978-1992 ). Journal of Epidemiology, 11(4), 170–179.

These authors reported an association between fluoridation and a range of cancers. Problem is, they did not consider any other risk-modifying factors. When some geographical parameters were included in the statistical analyses there were no statistically significant relationships of cancer with fluoridation.

(see Fluoridation and cancer).

The Malin & Till (2015) ADHD paper:

Malin, A. J., & Till, C. (2015). Exposure to fluoridated water and attention deficit hyperactivity disorder prevalence among children and adolescents in the United States: an ecological association. Environmental Health, 14.

This reported an association of ADHD prevalence with the extent of fluoridation in the US. Anti-fluoride campaigners have cited this paper a lot because it is the only study indicating any effect of fluoridation on cognitive ability. All other studies they rely on were from areas of endemic fluorosis where the natural levels of fluoride are higher than that used in community water fluoridation.

Malin & Till (2015) considered only household income as a possible risk-modifying factor. No consideration was given to residential elevation which other researchers had around the same time reported as associated with ADHD prevalence.

I repeated their statistical analysis but included residential elevation and a range of other risk-modifying factors. This showed there was no statically signficant association of ADHD with fluoridation when other risk-modifying factors, particularly elevation, were included. My critique of Malin and Till (20215) is now published:

Perrott, K. W. (2017). Fluoridation and attention deficit hyperactivity disorder – a critique of Malin and Till ( 2015 ). Br Dent J.

(See ADHD linked to elevation not fluoridationADHD link to fluoridation claim undermined again and Fluoridation not associated with ADHD – a myth put to rest).

Ignoring the lack of explanatory power

I think this is where the over-reliance on statistical significance, the p-value, can be really misleading. Researchers desperately wishing to confirm their bias will proudly claim  a statistically significant relationship, a p-value less than 0.05, etc., as if that is the final “proof.” These researchers will often hide the real meaning of their relationship by not making the actual data available or limiting their report of their statistical analysis to p-vlaues and, maybe, a mathematical relationship.

However, if the reported relationship actually explains only a small part of the observed variation in the data it may be meaningless. Concentration on such a relationship means that other more signficant risk-modifying factors which would explain more of the variation are ignored. Anyway, where a factor explains only a small part of the variation it is likely a more complete statistical analysis would show that its contribution was not actually statistically signficant.

Some examples:

The prenatal fluoride exposure and IQ study of Bashash et al (2017):

Bashash, M., Thomas, D., Hu, H., Martinez-mier, E. A., Sanchez, B. N., Basu, N., … Hernández-avila, M. (2016). Prenatal Fluoride Exposure and Cognitive Outcomes in Children at 4 and 6 – 12 Years of Age in Mexico.Environmental Health Perspectives, 1, 1–12.

These authors reported a statistically significant association of Child IQ with the prenatal fluoride exposure of their mothers. However, their figures showed a very wide scatter in the data indicating very little explanation of the variation in child IQ by the association with prenatal fluoride. (see below left). This must be why the Fluoride Action Network removed the data points from the figure when reproducing it for their promotion of the paper (see below right).

Bashash et al., (29017) did not give the complete statistical analysis of their data. However, I was able to digitally extract the data from their figure and my analysis showed that prenatal fluoride expose was only able to explain a little over 3% of the variation in child IQ. So, despite the statistical significance of their observed relationship prenatal fluoride exposure is unlikely to be a real factor in child IQ. In fact, concentration on this minor (even if statistically significant) factor will only inhibit the discovery of the real causes of IQ variation in these children.

Yes, anti-fluoride campaigners will protest that this study did consider some other possible risk-modifying factors. However the very low-level of explanation of the variation in the data indicates they did not consider enough.

(see Premature births a factor in cognitive deficits observed in areas of endemic fluorosis? Fluoride, pregnancy and the IQ of offspring and Maternal urinary fluoride/IQ study – an update).

The Xiang et al., (2003) water fluoride and IQ study:

Xiang, Q; Liang, Y; Chen, L; Wang, C; Chen, B; Chen, X; Zhouc, M. (2003). Effect of fluoride in drinking water on children’s intelligence. Fluoride, 36(2), 84–94.

Anti-fluoride campaigners rely a lot on this and other papers from this group.  Even though this research involved areas of endemic fluorosis it, in a sense, provides some of their best evidence because they reported a dose-dependent relationship of IQ to water F. Xiang et al., (2003) claimed a statistically signficant association of child IQ to fluoride water levels.  Other anti-fluoride campaigners, and some other researchers, have cited Xiang et al., (2003) to support such an association.

I don’t question these researchers found a significant association – but there is a problem. Nowhere do they give a statistical analysis or the data to support their claim! Very frustrating for critical readers (and we should all be critical readers).

They did, however, give some evidence from a statical analysis of the relationship of IQ with urinary fluoride. They did not give a complete statistical analysis but they included the data in a figure  (see below) – so I did my own statistical analysis of data digitally extracted from the figure.

The figure shows a high scatter of data points so this is another case of a statistically significant relationship explaining only a small part of the variability. My analysis indicates the relationship explains only about 3% of the variability in IQ value. Another case where researchers have concentrated on their own pet relationship and in the process not properly searched for more reasonable risk-modifying factors capable of explaining a larger proportion of the variation.

I have made a more detailed critique of Xiang et al.  (2015) and Hirzy et al., (2016) which relies on this data (see Does drinking water fluoride influence IQ? A critique of Hirzy et al. (2016)). A paper based on this has been submitted to a journal for publication and is currently undergoing peer review..

(see Anti-fluoride authors indulge in data manipulation and statistical porkiesDebunking a “classic” fluoride-IQ paper by leading anti-fluoride propagandists,  Connett fiddles the data on fluorideConnett & Hirzy do a shonky risk assesment for fluoride and Connett misrepresents the fluoride and IQ data yet again).

Conclusion

This  briefly outlines the statistical problems of a number of papers anti-fluoride campaigners rely on. Two common problems are:

  • Insufficient consideration of confounders or other risk-modifying factors – indicating a bias towards a “preferred” cause, and
  • Reliance on a relationship that, although statistically significant, explains only a very small fraction of the observed variation – again indicating bias towards a “preferred” cause

I don’t for a minute suggest that only those researchers publishing “anti-fluoride” research are guilty of these errors. They are probably quite common. Authors will generally responsibly warn that “correlation does not prove causation” and suggest more work needs to be done including  consideration of a wider number of confounders or risk-modifying factors. However, bias is only human so researcher advocacy for their own findings is understandable. The published research may even be of general value if readers interpret it critically and intelligently.

However, in the political world such critical consideration is very rare. Activists will use published research in the way a drunk uses a lamppost – more for support than for illumination. This makes it important that the rest of us be more objective and critically assess the claims they are making. Part of this critical assessment must include an objective consideration of the published research that is being cited.

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More nails in the coffin of the anti-fluoridation myths around IQ and hypothyroidism

thyroid_fluoride

Large Canadian study finds no effect of fluoridation on thyroid health

A new Canadian study shows no relationship of cognitive deficits or diagnosis of hypothyroidism with fluoride in drinking water. This work is important because it counters the claims made by anti-fluoride campaigners. While the campaigners cite scientific studies to support their claims, those studies are usually very weak, or irrelevant because they involve areas of endemic fluorosis where drinking water fluoride concentrations are much higher than in situations where community water fluoridation (CWF) is used.

The study is reported in:

Barberio, A. M. (2016). A Canadian Population-based Study of the Relationship between Fluoride Exposure and Indicators of Cognitive and Thyroid Functioning; Implications for Community Water Fluoridation. MSc Thesis, University of Calgary

This new study is important as it has the advantages of using a large representative sample of the Canadian population, with extensive data validation and quality control measures. It also uses individual-level estimates of fluoride exposure on the one hand, and thyroid health and cognitive problems on the other.

Fluoride exposure was measured both by concentration in tap water for selected households and concentration in urine samples from individuals.

Thyroid health

The Canadian study found:

“Fluoride exposure (from urine and tap water) was not associated with impaired thyroid functioning, as measured by self-reported diagnosis of a thyroid condition or abnormal TSH level.”

This contradicts the conclusions from the population-level study of Peckham et al., (2015) which reported that fluoridation was correlated with the prevalence of hypothyroidism. That study is quoted extensively by anti-fluoridation activists but has been roundly criticised because it did not include the influence of confounders – particularly iodine which is known to influence thyroid health.

Barberio (2016) also suggests that the different recommended fluoride concentrations used for CWF in Canada and the UK, and the fact that the Peckham et al (2015) study did not involve individual measures, could also be factors in the different findings.

Cognitive functioning

The Canadian study reported:

“Fluoride exposure (from urine and tap water) was not associated with self-reported diagnosis of a learning disability.”

Barberio (2016) did also investigate a more detailed diagnosis for cognitive problems and found:

“Higher urinary fluoride was associated with having ‘some’ compared to ‘no’ cognitive problems . . . . however, this association:

  • Was weak;

  • Was not dose-response in nature; and

  • Disappeared when the sample was constrained to those for whom we could discern fluoride exposure from drinking water.”

I guess anti-fluoride activists might latch on to this last point regarding urinary fluoride but, at least as far as tap water fluoride is concerned, there was no relationship with learning difficulties.

Conclusion

So – yet another large-scale study contradicts anti-fluoridationist claims. It shows that CWF has no influence on cognitive problems or thyroid health.

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