Exposure to fluoridated water and attention deficit hyperactivity disorder prevalence among children and adolescents in the United States: an ecological association
Journal or Publication
Ashley J Malin, Christine Till.
Shivani Arora, BDS, MPH, CPH
Level of rigor
- A - Strong methodology and unbiased, appeared in peer-reviewed in respected science journal
- B - Strong methodology and unbiased, not in peer-reviewed journal
- C - Weak methodology and/or biased
- F - Not a scientific finding
Support from other studies
- High - All the peer-reviewed research to date support these findings, and a significant amount of research has been done in this area.
- Medium - Most, but not all, peer-reviewed research to date support these findings, and a significant amount of research has been done in this area.
- Low - Not a lot of research has been done in this area, or some, but not most, other peer-reviewed research supports these findings.
- Not Supported - No other studies support this study's conclusions.
- Contradicted - Most studies contradict this study's conclusions.
There are no strengths.
It's an ecological study design with 51 observations (50 states & DC), and is not appropriate to test a hypothesis. ADHD prevalence was based on self-reported data, and hence had a potential of misclassification of disorder status. State-wide fluoridation measures were used. Individuals' exposure to fluoridation were not measured. Due to ecological assessment of exposure to fluoride in drinking water and the use of prevalence data of self-reported ADHD and water fluoridation from different years, the findings are at high risk for ecological fallacy. Authors did not adjust for important confounders (smoking, low birth weight, age, sex etc.). Moreover, authors' poor literature review and skewed interpretation of literature concerning fluoride and neurodevelomental defects may have introduced bias.
Relevance and validity
They used life-time ADHD prevalence for their study. They should also have considered using current diagnosis of ADHD as the disorder regresses with age. Authors failed to control for important confounders (blood lead levels, smoking, low birth weight, gender etc.). This makes the internal validity questionable.