Title of study: Limitations of fluoridation effectiveness studies: Lessons from Alberta, Canada
Authors: Neurath C, Beck JS, Limeback H, Sprules WG, Connett M, Osmunson B, and Davis DR.
First Published: October 10, 2017
Abstract: A paper published in this journal, Measuring the short-term impact of fluoridation cessation on dental caries in Grade 2 children using tooth surface indices, by McLaren et al had shortcomings in study design and interpretation of results, and did not include important pertinent data. Its pre–post cross-sectional design relied on comparison of decay rates in two cities: Calgary, which ceased fluoridation, and Edmonton, which maintained fluoridation. Dental health surveys conducted in both cities about 6.5 years prior to fluoridation cessation in Calgary provided the baseline. They were compared to decay rates determined about 2.5 years after cessation in a second set of surveys in both cities. A key shortcoming was the failure to use data from a Calgary dental health survey conducted about 1.5 years prior to cessation. When this third data set is considered, the rate of increase of decay in Calgary is found to be the same before and after cessation of fluoridation, thus contradicting the main conclusion of the paper that cessation was associated with an adverse effect on oral health. Furthermore, the study design is vulnerable to confounding by caries risk factors other than fluoridation: The two cities differed substantially in baseline decay rates, other health indicators, and demographic characteristics associated with caries risk, and these risk factors were not shown to shift in parallel in Edmonton and Calgary through time. An additional weakness was low participation rates in the dental surveys and lack of analysis to check whether this may have resulted in selection biases. Owing to these weaknesses, the study has limited ability to assess whether fluoridation cessation caused an increase in decay. The study’s findings, when considered with the additional information from the third Calgary survey, more strongly support the conclusion that cessation of fluoridation had no effect on decay rate. Consideration of the limitations of this study can stimulate improvement in the quality of future fluoridation effectiveness studies.
The following graphs are from Chris Neurath, co-author of the report:
Feb 26, 2016, Response to the media clamor on the Calgary fluoride study: Omitted Data Shows Ending Fluoridation Has No Effects on Cavities, by Michael Connett (pdf of a power point)
• Oct 11, 2017, Press Release from Fluoride Action Network
• Oct 12, 2017, Calgary: Science on fluoride still not settled, Calgary Herald, by Licia Corbella
•• Published studies that reported on a decline in tooth decay rates after water fluoridation was stopped. See here.
2016 Some media reports in the Canadian Press on McLaren’s study:
Feb 17, 2016: CBC News (Canadian Broadcasting Corporation), Lack of fluoride in Calgary drinking water leads to rise in kids’ tooth decay, study indicates
Feb 17, 2016: The Globe & Mail, by Carrie Tait, Calgary study suggests kids have more cavities without fluoridation of water
Feb 17, 2016: Global News, by Carmen Chai, Here’s how removing fluoride from Calgary’s water affected kids’ teeth
Feb 17, 2016: Ottawa Citizen, Reevely: Calgary’s cavities show why Ontario should require fluoride in water supplies, By David Reevely
Feb 17, 2016: National Post, Edmonton kids have better teeth than those in Calgary because of fluoridated water, study says
Feb 19, 2016: Calgary Herald, Editorial: Nothing to smile about
Feb 19, 2016: The Globe & Mail, Opinion By Andre Picard: Why did Calgary cave to chemophobes over fluoridation?
Feb 19, 2016: National Post, Colby Cosh: Calgary, Edmonton and fluoride: In the teeth of a rivalry
Feb 22, 2016: Winnipeg Free Press, Calgary council revisits fluoride debate after study showing increased problems
Feb 23, 2016: MacLeans, Calgary revisits fluoride debate after study showing increased problems
Feb 23, 2016: Huffington Post, by Dan Arel, Calgary Removed Fluoride from Water and Saw an Increase in Tooth Decay,
Feb 25, 2016: The Globe and Mail, Why Calgary needs its fluoride, by Tom Flanagan, Professor of political science at University of Calgary
April 13, 2016: The Guardian (UK), Something in the water: is fluoride actually good for cities?
Excerpt: “… Some cities, including Calgary, Quebec City, Waterloo, Windsor and Saint John, have begun removing fluoride from their public drinking water – even as a study in Calgary just published by the city’s university shows tooth decay in children has worsened since the city stopped fluoridation in 2011…”
Sept 8, 2016: CBC News, Calgary fluoride decision from 2011 should now be reconsidered, councillors say
Sept 8, 2016: CTV News, Some councilors want to re-open debate on putting fluoride in the water supply, (Cynthia Roebuck, Anchor/Reporter)
Sept 12, 2016: National Post, Jen Gerson: Calgary’s poor suffered when city councillors bought into conspiracy theories about fluoride