Fluoride Action Network

Calgary Fluoride Study Fatally Flawed; Key Data Omitted

Fluoride Action Network | Bulletin | February 26, 2016

Last week, a “study” was published that claims ending fluoridation caused a dramatic spike in cavities in the city of Calgary, Alberta. The study, authored by a pro-fluoridation scientist, has fueled an aggressive lobbying and public relations blitzkrieg throughout Canada, with the aim of reversing Canada’s wise and steady trend away from fluoridation. The study is now being cited here in the U.S. as well.

Incredibly, however, the study OMITTED critical data that directly contradicts the study’s conclusion. The omitted data shows very clearly that the cavity increase in Calgary began BEFORE fluoridation ended, and — more importantly — that ending fluoridation had NO EFFECT on the cavity trend.

To help visualize this, we have put together the following figure which shows the omitted tooth decay data from Calgary’s three oral health surveys. As can be seen, the increase in tooth decay was occurring well before fluoridated ended, and it continued to occur at the same rate when fluoridation ended (in May 2011).


Yesterday, FAN issued a press release detailing the findings of our investigation, which I have included below.

As part of our investigation, I wrote to Dr. Trevor Sheldon, a renowned scientist who specializes in evaluating the effectiveness of medical treatments. Dr. Sheldon is the Dean of the Hull York Medical School and is familiar with the fluoridation issue, as he was one of the scientists who authored the British Government’s systematic fluoridation review (York Review), which found that — despite over 5 decades of fluoridating water — there has yet to be a single high-quality study to prove the benefits.

In my letter to Dr. Sheldon, I asked him if he could provide us his expert appraisal of this new pro-fluoridation study — which he very generously agreed to do. Dr. Sheldon is not a partisan in the fluoridation debate; he has not taken a position on the issue, one way or the other. In his analysis, however, Dr. Sheldon demolishes the Canadian study, laying bare its myriad problems, including the big elephant in the room — i.e., that the omitted data shows no apparent increase in cavities after fluoridation ended.

Dr. Sheldon’s expert conclusion is that the Calgary study does “not provide a valid assessment of the effect of fluoridation cessation.” You can read Dr. Sheldon’s entire statement on our website here.

In addition to Dr. Sheldon’s statement, I have put together a short presentation which explains, in step-by-step fashion, how and why the omitted data undermines the conclusion of the Canadian study. I have posted this presentation to the FAN website, both as a powerpoint file, and as a pdf file.

Based on the blitzkrieg we have seen this past week, I expect that the pro-fluoridation forces will continue to use this new “study” as a hammer to pressure local officials into supporting fluoridation. It is imperative, therefore, that we let our local and state officials know the other side of the story — the side that the media has thus far been unwilling to tell.

Michael Connett
Executive Director
Fluoride Action Network


FAN Press Release:

Calgary Fluoride Study Fatally Flawed; Key Data Omitted

A recently published study concludes that tooth decay rates in Calgary, Alberta, have increased because of the city’s decision to scrap its fluoridation program. But the study omits data showing that the spike in decay mostly occurred when fluoride was still in the water and used methods that a leading scientist says do “not provide a valid assessment.”

In recent years, dozens of Canadian communities, including Calgary, have stopped fluoridating water, citing concerns about safety, effectiveness, and cost. The number of Canadians drinking fluoridated water has plummeted by over 30% since 2005.

Now a new study is fueling a lobbying blitzkrieg, with calls for Calgary and other non-fluoridated Canadian cities to resume fluoridation, based on claims that Calgary children suffered a dramatic spike in cavities in the three years following fluoridation’s end in 2011.

The study, however, is riddled with problems, and is “not a valid assessment of the effect of fluoridation cessation,” says Dr. Trevor Sheldon, Dean of Hull York Medical School and scientist who specializes in evaluating the effectiveness of health care interventions, including fluoridation.

The study determined Calgary’s pre-cessation cavity rate based solely on a survey conducted 6 years prior to fluoridation ceasing, even though another survey was conducted just 1 year prior to fluoridation ending.

The omitted survey, conducted in 2009/10, shows that most of Calgary’s increase in tooth decay occurred while Calgary was still adding fluoride to its water. As Sheldon explains, the omitted data “shows a higher average annual rate of increase in [tooth decay] in the period before cessation (7%) than in the period which includes years after cessation in Calgary (5%).”

Says Sheldon, “this is contrary to what one would expect if fluoridation cessation was the primary driver of increases in caries over the period.”

The increase in cavities seen in Calgary is not unusual, but part of a larger trend. Tooth decay in baby teeth has been on the rise since the 1990s throughout North America, including in fluoridated cities like Edmonton.

“To imply that ending fluoridation is the cause of Calgary’s increased decay while omitting data which shows that most of the decay occurred when fluoride was still in the water, raises serious questions about the study’s credibility,” says attorney and FAN Executive Director, Michael Connett. “The aggressive, orchestrated way this study has been rolled out to pressure city councilors to resume fluoridation raises the specter of a politically motivated study.”

The lead author of the study, Lindsay McLaren, is not an independent scientist on the fluoridation controversy.

McLaren currently serves as a member of the Alberta Health Services’ Community Water Fluoridation committee, has written pro-fluoridation commentaries, and, in 2013, spearheaded a successful effort to convince the Alberta Public Health Association to begin lobbying for fluoridation.

Correction (2/26/16): An earlier version of this press release incorrectly stated that the 2009/10 survey was a larger, more comprehensive survey than the 2004/05 survey. The two surveys were roughly the same size, with 599 second graders examined in the 2004/05 survey, and 577 second graders examined in the 2009/10 survey.

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