The following is a guest blog post by Alan Cassels, a pharmaceutical policy researcher at the University of Victoria and the author of Seeking Sickness: Medical Screening and the Misguided Hunt for Disease (Greystone, 2012). The opinions are his; you are welcome to your own.
No randomized trial has ever been done to prove if adding fluoride to drinking water reduces cavities. What we know about fluoridating water supplies has come from epidemiologic and ecological studies comparing rates of tooth decay in fluoridated versus non-fluoridated communities.
Even though these limited ecological studies have delivered most of what we think we know about the benefits and harms of fluoridated water, it’s hard to imagine a new study shedding much light on this contentious issue. Marked by acrimony and controversy, the fluoridation debate has become something of a public health quagmire—one that you’d be well advised not to set foot in for fear of getting sucked permanently to the bottom.
And yet Newsweek waded into the quicksand last week with this story reporting on a recent study that adds another potential black mark on fluoride. Or maybe not. This time the suggestion is that fluoridated water might be unintentionally adding to our epidemic rates of Attention Deficit Hyperactivity Disorder (ADHD). The story lays out the association, reported in the journal Environmental Health, very clearly: “Parents reported higher rates of medically-diagnosed ADHD in their children in states in which a greater proportion of people receive fluoridated water from public water supplies.”
No wild or bombastic claims here, so let’s give Newsweek high marks for avoiding easy sensationalism, even as they might have missed the boat in discussing the research that supports fluoridated drinking water for dental health. One is left wondering—amid all the ecological and animal studies, the mechanistic or the cohort-based explanations of the dangers of fluoride —is there actually any good evidence to support drinking water fluoridation in the first place?
The story discusses fluoride research with considerable context and history, which tends to deflate the story’s initial assertion that this is the “first time that scientists have systematically studied the relationship between the behavioral disorder and fluoridation.” Newsweek’s story refers to dozens of studies over the last few decades where water fluoridation has been linked to the state of our teeth, our thyroids, our endocrine systems, and even our IQs. Fluoride, among other chemicals, has been previously described as a developmental neurotoxicant potentially linked to ADHD and other disorders. This is certainly not the first time that fluoride and ADHD have been connected with one another in the scientific literature, and I don’t think it will be the last.
But where does this leave us? As we know, ecological associations are on the lower tier of the evidence pyramid, and there are dozens of other associations that could affect ADHD rates that have absolutely nothing to do with fluoride. What about kids who live in jurisdictions with school systems incented to ramp up childhood medical diagnoses in order to get more state money for learning assistance workers? What about those areas that might have overactive ADHD associations, who are very energized to “educate” parents and teachers about the importance of early diagnosis? With what is largely a socially-constructed disease, blaming everything on a chemical culprit is clearly a little wrong-headed.
The report notes the limitations of such research and appropriately quotes an epidemiologist at the University of North Carolina, who concludes, “it would be ludicrous to draw a strong conclusion based on this study alone.”
I especially liked the fact the reporter did double time in gathering commentary across a wide spectrum of outside experts, quoting a Harvard epidemiologist, a UMass scientist who studies endocrine disruptors, a pediatrician and researcher at New York’s Mount Sinai Hospital, an NIH researcher, and a former risk assessment scientist at the Environmental Protection Agency.
Yet that extensive body of commentary seems to be missing one important thing: someone to stand up and say fluoridating our water is ultimately a good thing to prevent cavities. While it might be hard to track down a CDC official before deadline, the CDC’s website is replete with factsheets (some of them curiously quite dated) supporting community water fluoridation.
Newsweek references a range of prior research and experiments to at least partly explain fluoride’s potential adverse influence on brain development, including how it affects plumbing (fluoride increases absorption of a known neurotoxin, lead, from lead pipes). People wondering about the breadth of fluoride research are going to learn that there actually is a large body of ecological research that shows links (not causes) between fluoride-induced stained and mottled teeth and lower IQs, as well as references to studies showing geographical links between areas of high concentrations of water fluoridation, effects on thyroid function and lower IQs.
Readers might be disappointed that they can’t draw any conclusions from this kind of research, but I’m reminded about the early research on tobacco. No randomized trials were done to definitively prove the effects of tobacco on lung cancer, and it took forty years of dogged ecologic and epidemiologic research for a strong anti-tobacco public health message to emerge that suggested, but couldn’t prove, a causal connection.
One thing is for sure: this study reminds us that what we know, or think we know, about public health measures might be wrong. We can’t say this story has gotten even close to the bottom of the truth about the benefits and harms of fluoridating the water supply and its effects on behavioral problems in our children. But in capturing the issue in an engaging and entertaining article, it makes us want to keep asking questions.