Category Archives: SciBlogs

Cochrane fluoridation review. II: “Biased” and poor quality research?

Avoid-despair-about-biases

Here again, the language used in the Cochrane review (Water fluoridation for the prevention of dental caries) is very misleading. Especially when cherry-picked and taken out of context. The word “bias” used in the review does not have the meaning an uninformed reader might think.

It does not mean motivated experimental design or selection of data to “prove” a predetermined outcome. Rather it has specific meaning related to common (and usually innocent) problems encountered clinical drug trials. These problems also occur in real-life epidemiological studies and trials of the sort used for evaluating social health measures like community water fluoridation (CWF) but the lack of control in such studies means they are harder to combat.. The Cochrane ideal of randomised double-blinded trials is just not realistic in these situations. As the American Academy of Pediatrics comments in their article on the Cochrane review:

“it would be a logistical nightmare to try creating a public water system that pumps fluoridated water to the first house on the block, delivers non-fluoridated water to the following two houses and then provides fluoridated water to the 4th and final house on that block.”

The review describes the types of “biases”  considered:

“Assessment of risk of bias in included studies
. . . . . The domains assessed for each included study included: sampling, confounding, blinding of outcome assessment, completeness of outcome data, risk of selective outcome reporting and risk of other potential sources of bias. . . . . .  We had identified the following factors as important confounders for the primary and secondary outcomes: sugar consumption/dietary habits, SES, ethnicity and the use of other fluoride sources.”

Unfortunately, all these sorts of “biases” are inevitable to some extent in the real world. Researchers do not always have the budget to include consideration of all confounders, or the degree of control required. There are inevitable gaps in data when families move or withdraw children from schools. Yet it is real-world studies, not idealised laboratory experiments, that give the data and other evidence reviewers and decision-makers must consider. Humans can’t be treated like experimental rats.

What “biases” did the review find

As far as “caries outcome” is concerned the review reports a  “high risk of bias overall,” but this “bias may occur in either direction.” This indicates there is not a motivated selection of data or experimental design to produce a predetermined result as that would show up as a systematic bias.

The major cause of “bias” arose from lack of control of the confounding issues of “sugar consumption/dietary habits, SES, ethnicity and the use of other fluoride
sources.” These are of course important factors which could influence results. In the real world it is difficult to control of variations in dietary intake, although socioeconomic status (SES) and ethnicity can be included in statistical analyses of data. My impression is that this is usually done in more recent studies (which the Cochrane review team had excluded from their review – see Cochrane fluoridation review. I: Most research ignored).

Most studies were at low risk of “bias” from sampling methods but on “detection bias” the reviewers report:

The majority of the studies did not blind outcome assessors. This is perhaps unsurprising when considering the efforts that may be required to blind assessors for this type of study.”

The qualification here surely indicates the inadequacy of the Cochrane criteria for using word’s like “bias” which are more fitted to clinical drug trials than evaluation of social health policies.

Most studies did not suffer from “incomplete outcome data” where some data is not measured, but some showed the “bias” of “selective reporting” where data sets reported were incomplete. Interestingly the reviewers report one study where:

“the baseline fluoridation status of the children was determined by the location of the school they attended, which may not have taken into account any children attending schools in fluoridated areas who resided outside those areas.”

This must be a common problem researchers face when they do such real-world epidemiological studies.

Inappropriate criteria used to judge quality of research

Given the nature of evaluating a social health policy like community water fluoridation (CWF) I think the criteria used by the review team to judge the quality fo available research was quite wrong. Their criteria were more fitted to judging clinical drug trials and not social health policies. They acknowledge this in their discussion section “Quality of evidence:”

“However, there has been much debate around the appropriateness of GRADE when applied to public health interventions, particularly for research questions where evidence from randomised controlled trials is never going to be available due to the unfeasibility of conducting such trials. Community water fluoridation is one such area.”

And:

“we accept that the terminology of ’low quality’ for evidence may appear too judgmental. We acknowledge that studies on water fluoridation, as for many public health interventions, are complex to undertake and that researchers are often constrained in their study design by practical considerations. For many public health interventions, the GRADE framework will always result in a rating of low or very low quality. Decision makers need to recognise that for some areas of research, the quality of the evidence will never be ’high’ and that, as for any intervention, the recommendation for its use depends not just upon the quality of the evidence but also on factors such as acceptability and cost-effectiveness (Burford 2012).” My emphasis.

These are important qualifications which, however, did not make it into the review’s Abstract or Plain Language Summary – and certainly not into media reporting. I think the review team was irresponsible to omit such qualifications from their summaries – and many people might suggest they were irresponsible to use such inappropriate criteria for their judgements in the first place.

The scientific literature is not perfect

I keep stressing that readers should always approach scientific reports and papers critically and intelligently. The problems identified by the Cochrane reviewers are inevitable and should always be taken into account by sensible readers. Simple reliance on the abstract of a paper or report often gives a misleading interpretation of the findings. Unfortunately, even unmotivated reporters tend not to read reports in full. Motivated activists will purposely resort to cherry-picking and distortion.

Decision-makers don’t necessarily need perfect scientific papers as they have to consider far more than the abstract conclusion of a scientific paper. There are the democratically expressed views of the electorate and the real situation where social health policies are put into effect. While the Cochrane reviewers expressed “limited confidence” in the size of the effect of CWF on tooth decay. However, policy-makers are more interested in the fact that there is a positive effect on oral health than the possible “theoretical” size of that effect.After all, policy-makers have to also consider the possible role of confounding effects like alternative sources of fluoride, the quality of dental health in the area, socioeconomic status of the population and school health programmes when making decisions about local CWF programmes.

Conclusions

1: The Cochrane reviewers’ use of terms like “bias” and judgment of studies as being of poor quality is inappropriate for evaluation of a social health policy. According to them:

“The main areas of concern were confounding and lack of blind outcome assessment. The evidence was additionally downgraded for indirectness due to the fact that about 71% of the caries studies that evaluated the initiation of water fluoridation were conducted prior to 1975.”

Yet they qualify this by acknowledging such judgement of “bias” and poor quality is inappropriate for a social health policy. And it was their own criteria for rejecting studies that produced a paucity of more recent studies (see Cochrane fluoridation review. I: Most research ignored).

2: These qualifications were not mentioned in the review’s Abstract or Plain Language Summary. I believe this was irresponsible of the authors. especially  given the controversial nature of the subject and the well-understood fact that media reporters rarely read beyond abstracts and summaries.

Such inappropriate and unqualified language provides a godsend to anti-fluoridation propagandists who are already cherry-picking and misrepresenting the review’s main findings.

3: We can remove the inappropriate and judgmental language and still accept that many of the problems identified in the review are inevitable for studies of social health measures. The review actually acknowledges that.

However, the sensible reader of scientific literature is surely aware of these problems. Any research paper must be assessed intelligently and critically – especially regarding the treatment of confounding factors. This is a point I have continually stressed in my posts on this subject.

In my experience, it has been the confirmation bias of anti-fluoride activists which leads them to ignoring such advice. One need only consider their use of studies related to IQ and fluoride in areas of endemic fluorosis, or their recent promotion of poor quality papers claiming a relationship between CWF and Attention-Deficit Hyperactivity Disorder (see ADHD linked to elevation not fluoridation) or hypothyroidism (see Paper claiming water fluoridation linked to hypothyroidism slammed by experts). 

I urge readers to follow this same advice with the Cochrane review. Don’t accept media reports or a limited reading of its Abstract or Plain Language Summary.

Read the whole review – intelligently and sceptically.
See also:

Cochrane fluoridation review. I: Most research ignored

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Cochrane fluoridation review. I: Most research ignored

With the publication of the new Cochrane Fluoridation Review (Water fluoridation for the prevention of dental caries) we have, once again,  both fluoridation supporters and opponents claiming it as evidence for their contradictory positions. They surely both cannot be right.

The reality is that any such review is going to have its own complexities and limitations which allow committed believers on either side to confirm their biases. Unfortunately, this confirmation bias is promoted by inadequate reporting relying on “sound bites” from the executive summary.  Real understanding of the review and its results requires more thoughtful analysis, a reading of the full review and not just media reports and a bit of thinking about its limitations.

The post is the first of three articles looking a bit more deeply at the Cochrane fluoridation review. Here I discuss the strict criteria used by the review team for selecting the studies they considered,  the limitations this has caused for their findings and the misinterpretation of the review results this has produced.

97% of fluoridation research ignored

This seems amazing – why ignore so much of the research? We can understand the need to filter poor research or poorly reported claims. But 97%?

Yet, that is what the review reports – and summarises in their Figure 1:

Cochrane-1

The high exclusion rate was caused by the review teams decision to only consider studies which conformed to strict criteria:

“For caries data, we included only prospective studies with a concurrent control, comparing at least two populations, one receiving fluoridated water and the other non-fluoridated water, with at least two points in time evaluated. Groups had to be comparable in terms of fluoridated water at baseline. For studies assessing the initiation of water fluoridation the groups had to be from nonfluoridated areas at baseline, with one group subsequently having fluoride added to the water. For studies assessing the cessation of water fluoridation, groups had to be from fluoridated areas at baseline, with one group subsequently having fluoride removed from the water.
For the purposes of this review, water with a fluoride concentration of 0.4 parts per million (ppm) or less (arbitrary cut-off defined a priori) was classified as non-fluoridated.”

This criteria requiring measurements at several time periods and the inclusion of data from before the commencement of fluoridation was probably the main reason for excluding studies. In the review’s Table “Characteristics of excluded studies” the most often mentioned reason was “Evaluated caries in a single time point cross-sectional study.”

OK, you can sort of see the logic behind these strict criteria:

“The cross-sectional studies, whilst able to provide information on whether water fluoridation is associated with a reduction in disparities, are not able to address the question of whether water fluoridation results in a reduction in disparities in caries levels.”

But this inevitably resulted on consideration of only a small part of the available research:

“155 studies (162 publications) met the inclusion criteria for the review. However, only 107 studies (15 caries studies; 92 studies reporting data on either all fluorosis severities or fluorosis of aesthetic concern) presented sufficient data for inclusion in the quantitative syntheses.”

Inability to comment does not mean no effect

Exclusion of so many important studies meant the review was unable to come to any conclusions about important aspects like the effect of community water fluoridation (CWF) on socioeconomic difference in tooth decay,  the effect of stopping CWF programmes on later tooth decay and the effectiveness of CWF in reducing adult tooth decay.   Yet, in the review’s discussion they did make note of research which did draw some conclusions in these areas – research they refused to consider. (And it is rather ironic that one of the review’s authors, Helen V. Worthington, has co-authored several papers which conclude that CWF does reduce socioeconomic differences in dental health).

Of course, anti-fluoride propagandists have chosen to misrepresent the review – reporting its inability to draw conclusion on these questions as evidence that CWF does not influence socioeconomic differences, is not effective for adults and tooth decay does not increase when CWF is stopped!  (See Misrepresentation of the new Cochrane fluoridation review). Clear misrepresentation – but helped by the combination of exclusion of most research and the  vague language used in the review summary.

And you do sort of wonder at ignoring so much evidence when considering issues related to community health. Was Cochrane throwing away the baby with the bathwater?

Confirmation fluoridation is effective

The strict exclusion criteria enabled the review team to winnow studies down to a small number which could be analysed quantitatively. They were able to confirm from analysis of 9 studies that CWF:

“resulted in a 35% reduction in decayed, missing or filled baby teeth, and 26% reduction in decayed, missing and filled permanent teeth.”

But the strict exclusion criteria, specifically rejection of cross-sectional studies, is still a fly in the ointment. Recent studies of situations where fluoridation has been in operation for a long time did not fall within the strict selection criteria because pre-fluoridation data would not realistically be available in most cases. The review consequently did not consider properly the recent evidence – 71% of the research considered occurred before 1975!

The review, therefore, raised the issue of how applicable their findings are to the current situation in developed countries because of improved dental care and use of fluoridated toothpaste. A reasonable proviso which could have been discussed properly using the research they had excluded. But again a proviso which enables misrepresentation by anti-fluoride propagandists who imply that their findings are irrelevant to our current situation.

The review authors acknowledge that exclusion of such data presents a problem for their conclusions:

“In the past 20 years, the majority of research evaluating the effectiveness of water fluoridation for the prevention of dental caries has been undertaken using cross-sectional studies with concurrent control, with improved statistical handling of confounding factors (Rugg-Gunn 2012). We acknowledge that there may be concerns regarding the exclusion of these studies from the current review. A previous review of these cross-sectional studies has shown a smaller measured effect in studies post-1990 than was seen in earlier studies, although the effect remains significant. It is suggested that this reduction in size of effect may be due to the diffusion effect (Rugg-Gunn 2012); this is likely to only occur in areas where a high proportion of the population already receive fluoridated water.”

Of course, the review team was correct to raise the question of the possible reduced efficacy of CWF in modern developed societies. But doesn’t that suggest they should not have used such restrictive criteria in selecting studies to consider? And isn’t it irresponsible to leave the impression that CWF is no longer effective when they excluded the studies which could have provided better answers?

Conclusion

The Cochrane fluoridation review suffers from the fact that only 3% of available studies were considered. The restrictive selection criteria enable quantitative estimates showing  CWF is effective for children but excluded the possibility of answering questions related to the effectiveness for adults, the ability of CWF to reduce socioeconomic differences in oral health,  the effect of stopping fluoridation on later tooth decay and whether improved availability of dental treatments and use of fluoridated toothpaste has reduced the efficacy of CWF in modern developed societies.

The language of the review report itself encourages misinterpretation – and this is even worse in their blog post about the review – Little contemporary evidence to evaluate effectiveness of fluoride in the water.” Here they repeatedly refer to lack of evidence but only explain this is due to their exclusion of such evidence in a few places. What is the uninformed reader, who does not bother to read the full document, make of points in the summary such as:

  • “There is insufficient evidence to determine the effect of water fluoridation on disparities in caries levels across socio-economic status
  • There is insufficient evidence to determine the effect of water fluoridation on caries levels in adults
  • There is insufficient evidence to determine the effect of removing water fluoridation programmes from areas where they already exist”

Finally, anti-fluoride propagandists are motivated enough to misrepresent the findings in any fluoridation review or other documents. The very restricted selection criteria used by the Cochrane review and the language of its summary and news reporting of the review is a bit of a godsend to such propagandists.

Expect to see a lot of cherry-picked quotes from the Cochrane review. Twisted to turn the lack of evidence of effects (due to the exclusion of studies) into evidence for no effect.


My next article on the Cochrane review will deal with its discussion of “bias” and poor quality in the studies it considered.

See also:

Misrepresentation of the new Cochrane fluoridation review

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What is causing warming of the earth?

Bloomberg has a great article showing why climate change deniers have it all wrong when they argue that the observed global warming is explained by natural causes. It just isn’t. The article is What’s Really Warming the World? Climate deniers blame natural factors; NASA data proves otherwise.

Here are the main points and graphics which compare the observed changes in earth’s temperature  with the changes expected from individual factors:

Natural factors

Changes in the earth’s orbit around the sun (blue line) have had a negligible effect on warming:

Sun

Changes in the sun’s temperature (orange line)have also had a negligible effect:

Solar

Volcanos influence the earth’s temperature, usually causing decreases,(red line) but cannot explain the observed warming:

Volcanic

Natural factors combined (earth’s orbit, sun temperature and volcanoes) (green line) cannot explain the observed warming:

Natural

Human factors

Changes in land use, like deforestation, (light green line) actually have a cooling effect:

Land-use

Ozone level changes (light blue line) have only a slight warming effect:

Ozone

Aerosol pollution (purple line) has had a marked cooling effect:

Aerosol

Greenhouse gas concentration increases (green line) have had a marked warming effect – it is clearly the main factor responsible for global warming:

Greenhouse-gases

When all the human factors, ozone, land use, aerosols and greenhouse gases, are combined the models (blue line) show a good agreement with observed temperature changes (black line):

Human

Natural and human factors combined

When all the natural and human factors are combined (red line) agreement between the modelling and observed earth temperatures is even better.

total

 

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New science bloggers wanted for Sciblogs 2.0

Sciblogs 2.0 coming soon

After nearly six years in operation, Australasia’s largest blog network is getting a facelift and some fresh voices.


Sciblogs features commentary from around 30 scientists and science writers and is consistently ranked among the country’s top 10 blogs based on Sitemeter statistics.

But the platform is well overdue for a revamp and will soon be relaunched with a new look, new additions to the blogging line-up and a remit of appealing to a wider audience.

Among the changes will be:

  • A more visual look and refreshed blog homepages
  • Mobile-friendly design so Sciblogs looks good on smartphones and tablets
  • Some new bloggers covering everything from drones to psychology
  • News content drawing from sources such as our new Scimex.org research news portal.



Become a Scibling

We are on the lookout for new science bloggers to join our lively stable of bloggers and as well as writers, videographers and social media gurus who are passionate about science communication and who are keen to collaborate on Sciblogs.

“The likes of Iflscience, Science Alert and the science blog networks of Scientific American and Scienceblogs shows there’s strong appetite for science news and commentary,” said Sciblogs editor and SMC Director, Peter Griffin.

“We want to grow the Sciblogs community featuring the best, most interesting science from New Zealand and around the world. We’ll improve our mobile and social media presence so Sciblogs content is easier to browse and share.”

The new Sciblogs will go live by the end of August – contact Sciblogs editor Peter Griffin if you would like to get involved.

Gagging of scientists – a common problem?

worst-part-of-censorship-button-0874

A recent NZ Association of Scientists survey indicates that 40% of NZ scientists report they feel gagged from communicating their scientific findings to the public. Management policies and funding problems were blamed and there are issues around “embarrassing the government.”

The Science and Innovation Minister, Stephen Joyce, is not convinced by the survey results but is unwilling to accept there is a problem without  “a heck of a lot more evidence than we’ve got from one write-in survey.” (See Call for closer look at scientists’ claims | Radio New Zealand News.)  You can be sure he won’t go out of his way to look for such evidence.

Wider than direct censorship

Despite Joyce’s attempts to “turn a blind eye,” I think there is a problem and can certainly remember examples from my time working in a Crown Research Institute (these problems may not be as bad in the Universities). But the problem is wider than direct censorship – limiting publication because of commercial sensitivity, protection of intellectual property,  fear of scaring away or offending potential funders and succumbing to legal action – or just threats of legal action – from commercial interests.

There is also the gagging effect arising from the institutional culture, the attitudes and perceived interests of management bureaucracy, the old-boy network (which these days incorporates people from the commercial  sectors as well as the government and political system). I experienced an example of the old-boy network when a National MP attempted to get my director to “discipline” me because I had made a public statement on nuclear disarmament! I am sure this sort of “behind the scenes” pressure is exerted all the time on research institute managements by commercial and political figures. And how often do management figures consider the interests of freedom of expression and information, or the responsibility of science to communicate with the public, when subjected to such pressure with its implied threats to the funding or “name” of the institute?  Or to the career of the management figure themselves?

Wider than one’s own research

The issues, for and against, may be fairly clear when the findings being gagged are the research results of the scientists themselves. But scientists do have the responsibility to speak up about science itself, and about general findings which may not be directly linked to the narrow field of specialisation of the scientist concerned.

This is especially true today when so much pseudoscience and outright distortion of science is promoted in the public sphere. Very often the promotion is done in the interests of business so managements may feel the need to prevent staff from fulfilling such responsibilities so as to avoid commercial pressures on the institute.

A common example is the scientific misinformation peddled by the “natural”/alternative health industry, which today is a big and profitable business – despite attempting to present itself as the “David” challenging the “Goliath” of “Big Pharma.”

Institutional management may pressure staff not to face up to their responsibility to fight this misinformation – especially if they believe there may be possibilities of research contracts from businesses within that industry. Maybe management will express this in relatively bland terms such as the need to protect the “name” and “reputation” of the institute. Or express the concept that the institute should not be seen to be “taking sides” as this undermines its credibility and appearance of objectivity.

Becoming a “street fighter” or abdicating scientific responsibility?

Then, of course, there is just the outright viciousness of some anti-science campaigners. Getting into public fights with some ideologically motivated activists can be like participating in a pub brawl. Responsible management cannot be happy about staff being seen as “street fighters.”

Management also has a responsibility not to expose their staff to danger. In New Zealand District Health Boards have tended not to take part in public meetings which are stacked with anti-fluoride activists – partly for the safety reason. And recent reports of attacks on health spokespersons and city council leaders, by anti-fluoride activists, show this is a reasonable concern (see  Lismore mayor assaulted in broad daylight by fluoride-hater, and Beware the violent antis – Lismore Mayor physically assaulted).

33618It is a complex issue. On the one hand engagement with those who are misrepresenting science can sometimes end up like fighting a pig – one’s opponent is so slimy they can escape from any rational debate and the expert ends up just a dirty as the pig in the end. In the other hand not to take part in the public debate  results in the abdication of our scientific responsibilities and handing over the public issue to those who promote misinformation and pseudoscience. (In NZ anti-fluoride propagandists are continually claiming  the refusal of district health boards to front up to their meetings as evidence that science does not support fluoridation!)

Social media

Social media can be just as nasty to pro-science people who attempt to challenge misrepresentation and pseudoscience (have a look at the abuse rendered by the Australian anti-fluoride propagandist Dan Germouse here). There is little point in engaging extremists on social media – unless one is sure there are other readers, or “lurkers,” who may learn something from the exchange.

But one thing is sure, advocates of science do not use social media as often or as effectively as they should. Studies do show that pseudoscientific groups and those peddling scientific misinformation tend to dominate social media like Facebook and Twitter. Social media can be effective in creating opinions – and anyway it is a popular forum which we ignore at our peril.  Scientists need to find ways to effectively take part in social media – if we don’t we are abdicating our responsibility to society to defend science and oppose misinformation.

Conclusion

Gagging of scientists is much wider than the few cases where publication of individual research findings is restricted.Unfortunately institutional culture, its conservatism, authoritarianism and bureaucracy, inhibit the freedom of scientists to take part in the public debate around scientific issues. They inhibit participation in social media where much of the public debate occurs (see Science and social media in new Zealand). Institutional culture can therefore restrict a scientist’s ability to fulfill his or her responsibility to communicate science to the public and to oppose widespread misinformation and pseudoscience.

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I wish more people were aware of this

fools

Misrepresentation of the new Cochrane fluoridation review

A new fluoridation review was published this week – Water fluoridation for the prevention of dental caries from the Cochrane Oral Health Group. It’s main message is:

“Data suggest that the introduction of water fluoridation resulted in a 35% reduction in decayed, missing or filled baby teeth and a 26% reduction in decayed, missing or filled permanent teeth. It also increased the percentage of children with no decay by 15%. These results indicate that water fluoridation is effective at reducing levels of tooth decay in both children’s baby and permanent teeth.”

So, of course, we now have to put up with anti-fluoridation propagandists as they scurry to misrepresent the review’s findings.

I have written before about how Stan Litras, a New Zealand anti-fluoride propagandist,  indulges in cherry-picking, misinformation and outright distortion  of the science (see for example  Cherry-picking and misinformation in Stan Litras’s anti-fluoride article). Well, he has been at it again – this time putting his talents for misrepresentation to use on the new Cochrane Review.

Stan has issued a press release, using his astroturf vanity project (Fluoridation Network for Dentists) – Gold Standard Fluoride Review Contradicts NZ Advice. He claims that the new review’s:

“findings are completely at odds with last year’s Royal Society review, which our government refers to as justification for promoting fluoridation.”

In fact just not true!

Let’s compare his claims with what the Cochrane review actually reported.

Adult benefits

Stan claims the review “finds the science does not support claims that water fluoridation is of any benefit to adults.” Of course, Stan is implying that the review investigated the situation for adults and found no benefit.

Completely wrong.

The review says:

“No studies met the review’s inclusion criteria that investigated the effectiveness of water fluoridation for preventing tooth decay in adults, rather than children.”

And later:

“Only one of these studies examined the effect of water fluoridation on adults (Pot 1974); the reported outcome for this study was the percentage of participants with dentures. There are no data to determine the effect of water fluoridation on caries levels in adults.”

The Cochrane reviewers just did not have any suitable studies fitting their strict criteria for analysis so they could draw no conclusion on this specific question. However, in the review’s discussion they do mention a comprehensive systematic review (Griffin et al., 2007) which attributed a 34.6% reduction of tooth decay in adults to community water fluoridation. The corresponding figure for studies published after 1970 was 27.2%

Social inequalities

Stan implies the review found that fluoridation did not “reduce social” inequalities.

Completely wrong again.

The review was not able to draw any conclusion related to social inequalities because it just did not have that information. it says:

“There was insufficient information available to find out whether the introduction of a water fluoridation programme changed existing differences in tooth decay across socioeconomic groups.”

The review team did find 3 studies reporting effects of water fluoridation on disparities in caries across social class. However, there were problems with all 3 studies meaning the data was not suitable for further analysis and this  prevented them drawing any conclusions.

Benefits when toothpaste used

Stan claims, or at least strongly implies,  the review indicates that community water fluoridation does not “provide additional benefits over and above topically applied fluoride (such as in toothpaste).”

Again, completely wrong.

The review specifically says:

“Data suggest that the introduction of water fluoridation resulted in a 35% reduction in decayed, missing or filled baby teeth and a 26% reduction in decayed, missing or filled permanent teeth. It also increased the percentage of children with no decay by 15%. These results indicate that water fluoridation is effective at reducing levels of tooth decay in both children’s baby and permanent teeth.”

It goes on to say:

“However, since 1975 the use of toothpastes with fluoride and other preventive measures such as fluoride varnish have become widespread in many
communities around the world. The applicability of the results to current lifestyles is unclear.”

So, it raises the possibility that the current efficacy of community water fluoridation in industrialised countries could be lower. However, they could not draw a conclusion on this because only 30% of the included studies took place after 1975.

The review team did attempt to look at factors such as sources of fluoride “(potential confounders of relevance to this review include sugar consumption/dietary habits, SES, ethnicity and the use of other fluoride sources)” but found this not to be possible:

“However, due to the small number of studies and lack of clarity in the reporting within the caries studies, we did not undertake these sub-group analyses.”

Stopping fluoridation

Stan claims (or at least strongly implies) the review shows claims “that tooth decay increases in communities when fluoridation is stopped” are incorrect.

Wrong again.

The review says:

“There was insufficient information available to understand the effect of stopping water fluoridation programmes on tooth decay.”

And:

“No studies that met the inclusion criteria reported on change in dmft or proportion of caries-free children (deciduous/permanent dentition) following the cessation of water fluoridation.”

The only study the review discussed was that of Maupome et al., (2001). This paper is often quoted by anti-fluoridation propagandists but those authors themselves commented on the difficulty of drawing conclusions from their data:

“Our results suggest a complicated pattern of disease following cessation of fluoridation. Multiple sources of fluoride besides water fluoridation have made it more difficult to detect changes in the epidemiological profile of a population with generally low caries experience, and living in an affluent setting with widely accessible dental services.”

Dental fluorosis

Stan claims the review “found that 40% of children in fluoridated areas have dental fluorosis.” However, the review does not compare the incidence of dental fluorosis in fluoridated areas and unfluoridated areas. It simply draws conclusions about the likely incidence of dental fluorosis at different fluoride intakes. This lack of comparison is unfortunate, although the omission may be due to the lack of suitable studies that survived their strict criteria.

So Stan’s claim is misleading because without considering dental fluorosis in the non-fluoridated areas it is not possible to attribute any responsibility to community water fluoridation. He has simply taken the reported estimate for a fluoride intake of 0.7 ppm (the concentration in fluoridated drinking water in NZ) without taking into account the occurrence of dental fluorosis in unfluoridated areas. Very misleading!

The review does, however, compare rates of dental fluorosis for different drinking water concentrations and we can draw some proper conclusions from these.

Total dental fluorosis. The review defines this as all the forms of dental fluorosis according to the Dean Index – from questionable to serious. (See Water fluoridation and dental fluorosis – debunking some myths for a discussion of the different forms of dental fluorosis). The graph below shows the reviews findings for the effect of fluoride exposure (drinking water fluoride concentration) on any dental fluorosis.

DF-2True, at 0.7 ppm (the usual concentration for CWF, this shows an incidence of 40%. But we can estimate the increase due to CWF by subtracting the incidence for non-fluoridated water. So the increase due to CWF would be 7% (using the review’s concentration for non-fluoridated water of 0.4 ppm) or 10% using a more realistic concentration of 0.2 ppm.

So Stan is quite wrong to imply CWF causes a total dental fluorosis increase of 40% – it is only 10% or less. However, even that figure is misleading.

Most dental fluorosis is not of aesthetic concern – in fact, the milder forms are often viewed positively from the point of view of the quality of life. So the review also considers dental fluorosis of aesthetic concern – which they define as the serious, moderate and mild forms of dental fluorosis (their inclusion of mild forms here is questionable). The graph below illustrates their findings for these forms of dental fluorosis.
DF-1

So, if we consider only those forms of dental fluorosis the review considers of aesthetic concern  then increases due to CWF amount to only 2% (using the reviews definition of non-fluoridated) or 3% using a more realistic concentration of 0.2 ppm for non-fluoridated.

This is a huge difference to the 40% claimed by Stan.

The review acknowledges that their inclusion of mild forms of dental fluorosis in their definition of dental fluorosis of aesthetic concern is questionable, saying “mild fluorosis may not even be considered an unwanted effect.” Most studies do not consider the mild forms undesirable. It is likely that most of the increase in “dental fluorosis of aesthetic concern” arising from community water fluoridation occurs in the mild forms.  So my suggestion of a 2 or 3% increase in “dental fluorosis of aesthetic concern” will be an overestimation.

It is unsurprising, then, that some cross-sectional studies do not detect any increase in undesirable dental fluorosis attributed to community water fluoridation. The figure below illustrates an example reported in the New Zealand in the 2009 New Zealand Oral health Survey (see Our Oral Health).

Conclusions

Once again this anti-fluoridation propagandist has been caught misrepresenting the scientific literature on this issue. And his misleading press release is being touted as gospel truth by anti-fluoridation groups in NZ and the USA.

It is pathetic such people have to resort to misrepresentation in this way. Surely it is a sign of desperation to use statements that no conclusions were possible on specific details (adult benefits, social inequalities, influence of toothpaste, and what happens when fluoridation is stopped) because no studies fitted the selection criteria as “evidence” that there is no effect.

References

Griffin SO, Regnier E, Griffin PM, Huntley V. (2007). Effectiveness
of fluoride in preventing caries in adults. Journal of Dental
Research 2007;86(5):410–5.

Iheozor-Ejiofor, Z., Worthington, HV., Walsh, T., O’Malley, L., Clarkson, JE., Macey, R., Alam, R., Tugwell, P., Welch, V., Glenny, A. (2015). Water fluoridation for the prevention of dental caries (Review). The Cochrane Library, (6).

Maupomé, G., Clark, D. C., Levy, S. M., & Berkowitz, J. (2001). Patterns of dental caries following the cessation of water fluoridation. Community Dentistry and Oral Epidemiology, 29(1), 37–47.

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Misrepresenting the York fluoride review

I have noticed a few “Letters to the Editor” and social media comments lately misrepresenting the “York review” on fluoridation so looked into the background of some of these claims.

The “York review” (McDonagh, et al., 2000) is one of the earliest authoritative and comprehensive reviews of the scientific literature related to fluoridation and resulted from a request by the UK Department of Health for:

“a systematic review of the evidence for the safety and effectiveness of water fluoridation based on the currently available evidence from population-based studies.”

As a systematic review it is a valuable resource for decision-makers so this review – together with later and more comprehensive reviews – is usually accepted as one of the most reliable sources of evidence for local bodies considering fluoridation  issues. However, this very authority leads to its misrepresentation by activists.

We are used to activists misrepresenting the evidence contained in such reviews, but I want to comment on the way anti-fluoride propagandists attempt to present the review authors as supporting anti-fluoride positions. In particular, the way they use quotes from anti-fluoride people who have some tenuous connection to the review. These quotes are presented as authoritative, consistent with the reviews findings and with the implications the people quoted were authors  or members of the York Fluoride Systematic Review Team – when they were not.

Review Team & Advisory Panel

The York Fluoride Systematic Review Team were the authors of the report. These authors and affiliation are:

  • Jos Kleijnen, NHS Centre for Reviews and Dissemination, York, UK
  • Marian McDonagh, NHS Centre for Reviews and Dissemination, York, UK
  • Kate Misso, NHS Centre for Reviews and Dissemination, York, UK
  • Penny Whiting, NHS Centre for Reviews and Dissemination, York, UK
  • Paul Wilson, NHS Centre for Reviews and Dissemination, York, UK
  • Ivor Chestnutt, Dental Public Health Unit, Cardiff, Wales, UK
  • Jan Cooper, Dental School, University of Wales College of Medicine, Cardiff, Wales, UK
  • Elizabeth Treasure, Dental School, University of Wales College of
    Medicine, Cardiff, Wales, UK

However, an advisory board was also appointed. This included representatives from “both sides of the fluoridation debate” as well as including neutral people. According to Richards et al., (2002):

“Although the advisory panel and review team agreed the results of the review, agreement was not reached about the conclusions or, more importantly, the implications of the review.”

Hardly surprising given the differing views on the issue. This article adds:

“Parties on each side of the controversy were reluctant to abandon their previous positions and endorse the review result whole-heartedly.”

The Systematic Review Advisory Panel members were:

  • Chair: Trevor Sheldon, York Health Policy Group, University of York, York, UK
  • Earl Baldwin of Bewdley, House of Lords, London, UK
  • Iain Chalmers, UK Cochrane Centre, Oxford, UK
  • Sheila Gibson, Glasgow Homeopathic Hospital, Glasgow, Scotland, UK
  • Sarah Gorin, Help for Health Trust, Winchester, UK
  • Mike Lennon, Chairman of the British Fluoridation Society, Department of Clinical Dental Sciences, University of
    Liverpool School of Dentistry, Liverpool, UK
  • Peter Mansfield, Director of Templegarth Trust, Louth, UK
  • John Murray, Dean of Dentistry, University of Newcastle, Newcastle
    upon Tyne, UK
  • Jerry Read, Department of Health, London, UK
  • Derek Richards, Centre for Evidence-Based Dentistry, Oxford, UK
  • George Davey Smith, Department of Social Medicine, University of Bristol, Bristol, UK
  • Pamela Taylor, Water UK, London, UK

Readers will see the mixed nature of this group so won’t be surprised there were fixed views which prevented their endorsement of the review findings and conclusions.

Opportunist quoting of minority views

Anti-fluoridation propagandists have made much of quotes from 2 advisory panel members – people who were not authors of the review and could not represent the review itself.

york_chairman_quote

Out of context quote from anti-fluoride site No Fluoride.

Professor Trevor Sheldon has made a statement emphasising the provisional nature of the reviews findings, commenting on the poor quality of much of the research of health aspects and stressing the limitations of the review and need for further work. His statement recognised  that fluoridation is effective at reducing tooth decay The quality of research on health effects has also improved in recent years. However, anti-fluoride people use the quote in attempts to undermine research showing the efficacy of fluoridation and the lack of harmful effects. It is more correct to say, as Newton et al., (2015) did recently:

“In general, the literature suggesting adverse health effects of fluoridation is characterised by poor-quality studies that do not adequately adjust for potential confounding variables.”

Please note, Sheldon was a member of the Advisory panel and not an author of the review.

Another quote which has been rehashed recently by activists is from Advisory panel member Peter Mansfield:

“No physician in his right senses would prescribe for a person he has never met, whose medical history he does not know, a substance which is intended to create bodily change, with the advice, ‘Take as much as you like, but you will take it for the rest of your life because some children suffer from tooth decay.’”

Users of the quote imply he was an author of the review report – for example “Mansfield took part in the University of York (in York, England) review of public water fluoridation in 2000.” He did not. He was merely a member of the Advisory Panel representing the views of anti-fluoridationists. Have a search for him on the internet (he is the Director of Templegarth Trust, Louth, UK) to get a picture of his alternative health views.

Conclusions

In  their article about the York Review Richards et al., (2002) indicate that this early review identified problems with review processes and existing knowledge which future work would overcome:

“Future research can be more efficient and sharply focused as a result of open reviews of this kind. A consensus on future research priorities was one result of this review. The eventual findings of future work are more likely to be debated rationally and achieve wide consensus than if the review had not taken place.”

Anti-fluoride propagandists are simply taking advantage of those early issues, and dishonestly implying that they out-of-context quotes they use were made by authors of the York review when they weren’t.

References

McDonagh, M. S., Whiting, P. F., Wilson, P. M., Sutton, a J., Chestnutt, I., Cooper, J., … Kleijnen, J. (2000). Systematic review of water fluoridation. BMJ (Clinical Research Ed.), 321(7265), 855–9.

McDonagh, M., Whiting, P., Bradley, M., Cooper, J., Sutton, A., & Chestnutt, I. (2000). A Systematic Review of Public Water Fluoridation. 258 pp. Full report.

Newton, J. N., Young, N., Verne, J., & Morris, J. (2015). Water fluoridation and hypothyroidism: results of this study need much more cautious interpretation. Journal of Epidemiology and Community Health, 69(7), 617–8. http://doi.org/10.1136/jech-2015-205917

Richards, D., Mansfield, P., & Kleijnen, J. (2002). Systematic review in scientific controversy: the example of water fluoridation, an open access reviewEvidence-Based Dentistry, 3, 32–34.

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Fluoridation: Misrepresenting the “saliva theory”

I sometimes wonder if anti-fluoridation propagandists are trying to extend their “freedom of choice” argument to the scientific facts themselves. Perhaps this is how they justify to themselves their frequent cherry-picking and misrepresentation of research.

A current example is Fluoride Free NZ’s (FFNZ) misrepresentation of the mode of action of fluoride in protecting existing teeth in Saliva Theory Critique. Nothing new here – it’s a rehash of an older article of theirs which I critiqued 2 years ago in Fluoridation – topical confusion. But it still contains the same misinformation.

Selective quoting

Again FFNZ  misrepresents the advice of the Center For Disease Control (CDC) by selective quoting. Here is the relevant section of the document (CDC, 2001. Recommendations for Using Fluoride to Prevent and Control Dental Caries in the United States). The FFNZ article quoted only the 2 sentences in red!:

“Saliva is a major carrier of topical fluoride. The concentration of fluoride in ductal saliva, as it is secreted from salivary glands, is low — approximately 0.016 parts per million (ppm) in areas where drinking water is fluoridated and 0.006 ppm in nonfluoridated areas (27 ). This concentration of fluoride is not likely to affect cariogenic activity. However, drinking fluoridated water, brushing with fluoride toothpaste, or using other fluoride dental products can raise the concentration of fluoride in saliva present in the mouth 100-to 1,000-fold. The concentration returns to previous levels within 1–2 hours but, during this time, saliva serves as an important source of fluoride for concentration in plaque and for tooth remineralization (28 ).”

Their misrepresentation claims (in their words) “The CDC acknowledges that fluoridated water has no cariostatic effect” because of the low concentration of fluoride in secreted saliva. However, the full quote shows that the CDC advised that “saliva is a major carrier of topical fluoride” and that “drinking fluoridated water” is one way of increasing saliva fluoride concentration sufficiently so that “saliva serves as an important source of fluoride for concentration in plaque and for tooth remineralization.”

FFNZ purposely confuses the issue by ignoring the direct transfer of fluoride from water and food to saliva, dental plaque and biological tissue in the oral cavity. These act as reservoirs which can top-up the fluoride concentration at the tooth surface and help prevent demineralisation (responsible for tooth decay in acid conditions) and remineralisation.

“Topical” role of fluoride at tooth surface

This figure from the CDC document cited above provides a simple illustration of the way that fluoride, from fluoridated water, helps prevent tooth decay with existing teeth.

Even this shows that the mechanism is far from simple as the process is influenced by the concentration of phosphate and calcium in saliva, as well as fluoride. I would add that organic material, such as proteins, will also influence the mechanism. Then there is a process of transfer of fluoride, and other ions, to saliva from reservoirs like plaque, the tongue and other biological tissues which are known to store fluoride. For example, Vogel (2011) states:

“Current models for increasing the anti-caries effects of fluoride (F) agents emphasize the importance of maintaining a cariostatic concentration of F in oral fluids. The concentration of F in oral fluids is maintained by the release of this ion from bioavailable reservoirs on the teeth, oral mucosa and – most importantly, because of its association with the caries process – dental plaque.
Oral F reservoirs appear to be of two types: (1) mineral reservoirs, in particular calcium fluoride or phosphate contaminated ‘calcium-fluoride-like’ deposits; (2) biological reservoirs, in particular (with regard to dental plaque) F held to bacteria or bacterial fragments via calcium-fluoride bonds.”

Confusing the concentration issue

The FFNZ article attempts to confuse the issue again by citing 5 studies they claim “show that fluoridated water is too low in fluoride to provide any topical benefit.” But, of course, a more honest approach to the scientific literature is to consider all studies (not just the ones confirming one’s bias) and check relevant experimental details.

The studies they cite were not aimed at determining a minimum concentration for the surface reaction at the tooth surface. They were laboratory studies, using bovine dental material, usually not taking into account the role of other ions like calcium and phosphate. Several were studying fluoride/sucrose solutions.

In contrast, the review by Buzalaf (2011), Mechanisms of Action of Fluoride for
Caries Control  found:

“very low fluoride concentrations (sub- ppm range) in solution are already able to substantially inhibit acid dissolution of tooth minerals [23, 27].”

This was confirmed in the review of Ten Cate & Featherstone (1991). They cited studies showing inhibition of demineralisation at fluoride concentrations as low as 0.2 ppm and 0.025 ppm (Margolis et al., 1986). They also mention the higher fluoride concentrations required when ions like calcium and phosphate are omitted.

Demonstrated inhibition of demineralisation at such low fluoride concentration when the other relevant minerals are present does raise the possibility that fluoride in secreted saliva may still play a role, despite the view expressed in the CDC document cited above. However, let’s stress here, one does not have to take sides on that particular debate to recognise that the saliva fluoride concentration resulting from transfer from food and fluoridated water in the oral cavity is high enough to play a protective role against tooth decay. Bruun & Thylstrup (1984), who reported the low concentrations cited by the CDC, concluded that:

“direct contact of the oral cavity with F in the drinking water is the most likely source of the elevated whole saliva fluoride and that the increased availability of fluoride in the oral fluids has an important relationship to the reduced caries progression observed in fluoridated areas.”

So, again, the real world is not as simple as suggested by those who seek only to confirm their biases.

References

Bruun, C., & Thylstrup, A. (1984). Fluoride in Whole Saliva and Dental Caries Experience in Areas with High or Low Concentrations of Fluoride in the Drinking Water. Caries Research, 18(5), 450–456.

Buzalaf M.A.R., · Pessan J.P., · Honório H.M., & ten Cate J.M, (2011). Mechanisms of Action of Fluoride for Caries Control. In Buzalaf MAR (ed): Fluoride and the Oral Environment. Monogr Oral Sci. Basel, Karger, 2011, vol 22, pp 97–114

Center for Disease Control, 2001. Recommendations for Using Fluoride to Prevent and Control Dental Caries in the United States).

Margolis, H. C., Moreno, E. C., & Murphy, B. J. (1986). Effect of Low Levels of Fluoride in Solution on Enamel Demineralization in vitro. Journal of Dental Research, 65(1), 23–29.

Ten Cate, J. M.; Featherstone, J. D. B. (1991). Mechanistic Aspects of the Interactions Between Fluoride and Dental Enamel. Critical Reviews in Oral Biology and Medicine, 2(2), :283–296.

Vogel, G. L., (2011). Oral Fluoride Reservoirs and the Prevention of
Dental Caries. In Buzalaf MAR (ed): Fluoride and the Oral Environment.
Monogr Oral Sci. Basel, Karger, 2011, vol 22, pp 146–157

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Fluoridation and horses – another myth

Readers following the fluoridation issue have probably come across claims fluoridated water can poison horses. This is just another case of scaremongering by anti-fluoride propagandists – but what is it based on?

The claims go back to Cathy Justus, a horse owner from Pagosa Springs, Colorado. She lost eight horses and four dogs and blames it on their consumption of fluoridated water – which she describes as a “virulent cumulative toxin.” She also claims to “have the sad distinction of owning the first horses to ever be diagnosed with “chronic fluoride poisoning” from artificially fluoridated municipal water.”

Of course, her claim to owning the first horses diagnosed with poisoning by fluoridated water sets off alarm bells straight away. What happened to all the other horses which have consumed fluoridated water? And how could her diagnosis be so different?

What to the experts say?

According to Associate Professor Cynthia Gaskill, toxicology section chief at the Veterinary Diagnostic Laboratory at the University of Kentucky (see Expert discusses fluoridated water and horses in Horsetalk.co.nz):

“A casual internet search of this topic can uncover alarming reports purporting fluoride poisoning in horses from fluoridated municipal water.

“These reports typically are published in non-peer reviewed sources and are missing important information necessary to confirm the diagnosis, to rule out exposure to other fluoride sources, and to eliminate other potential causes.

“A careful review of the peer-reviewed literature in reputable scientific journals showed no published reports documenting fluoride poisoning in horses due to ingestion of fluoridated public water.”

An expert with the Sonoma County Horse Council, Ted S Stashak, concluded in his article The Effects of Artificial Fluoridation of Water (AFW) on Horses:

“Evidence to date indicates that F concentrations allowable in US public water systems are well tolerated by horses and do not cause fluorosis. Supporting this, is a fact that many horses nationwide drink AFW as their major source of water and fluorosis is a  very rarely reported condition.”

Why is Cathy Justus so convinced?

It doesn’t take much background reading to see Cathy Justus may be suffering a bit of confirmation bias. In a long letter to the Baltimore Post Express in 2012 she describes her own beliefs and the symptoms of her animals (see Poisoned Horses: Fluoride debate continues). Have a read of at least some of it and you will get the idea.

Cathy is a dyed in the wool anti-fluoride propagandist. Her letter is full of all the “arguments” and relies on the usual anti-fluoride bibles like The case Against Fluoride, The Fluoride Deception, etc. The letter’s tone is typical of someone with these extreme views. So it comes as no surprise to find she is also Fluoride Action Network’s (FAN) National Spokesperson against Fluoride Poisoning in Animals.

She is convinced that her  animals’ problems were caused by fluoridated water (as are all the health problems humans currently have) and, in her own mind, that this is not observed by other horse owners just indicates their ignorance and brainwashing.

But wait, there’s more

Cath Justus searched around until she found a veterinary expert who agreed with her bias – in this case, Dr. Lennart Krook, Professor Emeritus, Cornell University. So this whole incident got into the “peer-reviewed” (?), “scientific” (?) literature. To be exact, 2 papers and an editorial in the journal Fluoride – which she describes as the “fluoride bible.” You can check them yourself:

  • Krook, L. P., & Justus, C. (2006). Fluoride poisoning of horses from artificially fluoridated drinking water. Fluoride, 39(March), 3–10.
  • Justus, C., & Krook, L. P. (2006). Allergy in horses from artificially fluoridated water. Fluoride, 39(June), 89–94.
  • Sauerheber, R. (2013). Racehorse breakdowns and artificially fluoridated water in Los Angeles. Fluoride, 46(December), 182–191.

As you might expect from that journal these papers are of poor quality – and, in particular, they present no evidence for the firm beliefs that fluoridated water was the cause of the problems described. Or their equally strong assertions that there is no possibility that feed contamination or other usual causes were absent. As Stashak says, these papers:

“are missing important information necessary to confirm that AFW alone was the cause for the signs of chronic fluorosis in these horses.”

A strongly held, motivated, anecdotal opinion is not evidence and would not be accepted as such by any self-respecting scientific journal. For the life of me, I cannot see how anyone could claim such papers are “peer-reviewed.”

All three authors are organisationally connected with the anti-fluoridation movement. Jutsus through here FAN position.  Krook through his membership of the anti-fluoride group Second Look‘s Advisory Board and his membership of the Editorial Board of Fluoride since 1990 and Associate Editor since 2003 (as described in his 2010 obituary of Fluoride).  Saueheber is part of James Deal’s (Attorney Deal) anti-fluoride Fluoride Class Action group.

Conclusion

This is just another example of the way anti-fluoride propagandists attempt to convert their biases into “facts.” They have produced multiple articles in the friendly “natural”/alternative health media, and even a video, to support this particular claim. Their tame “scientific” journal, Fluoride, has been dragged in to give academic credibility – and it is unlikely any reputable journal could have been used for this, given the lack of evidence.

In a rather pathetic footnote, Richard D Sauerheber, author of the editorial referred to, gives his institutional affiliation as University of California, San Diego, La Jolla, CA 92037, USA. He also did this in his one other published paper referred to in my post Calcium fluoride and the “soft” water anti-fluoridation myth. In our discussion there he admitted he does not work at that institution, although he did study there many years ago. This is the first time I have come across an author using their university of study as an institutional affiliation in this way. It is deceptive and aimed purely at attempting to claim credibility to himself and any article where he does this. I would be interested to know what officials at that university think of this practice.