There appears to be no relationship between fluoride exposure during youth and cognitive problems in adolescence or adulthood, according to an analysis of more than 10,000 individuals in Wisconsin published today in PNAS.Why It’s Relevant
A recent meta-analysis has suggested that early fluoride exposure might be detrimental to the brain, which has led several states to ban or consider banning fluoride in their water supply. However, the evidence linking fluoride to lower IQ is mixed, with most studies finding an association using data pulled from other countries, where fluoride levels in drinking water are much higher.
By the Numbers
- Researchers tapped into the Wisconsin Longitudinal Study (WLS) to examine cognitive outcomes for 10,317 Wisconsinites who graduated high school in 1957. These individuals were grouped into four categories: fluoride exposure from birth (people who lived near wells with naturally elevated fluoride), exposure after age 7 (municipal fluoridation efforts began in 1946), exposure after age 14, and no childhood exposure.
- There were no differences in average IQ scores at age 16 among any of the four groups after adjusting for sociodemographic or school-level variables.
- Similar findings were seen when examining children who lived in the same county their whole childhood (to ensure more consistent fluoride exposure).
- There were almost no fluoride-based differences in cognitive scores when the WLS participants were assessed at ages 53, 64, 72, and 80—outside of a tiny reduction in scores at age 53 in those exposed to fluoride before age 14 among the full sample (but not the subgroup who lived in the same county).
The Other Side
The researchers could only quantify whether the adolescents were in communities with access to fluoridated water and not how much fluoridated water they consumed. They also didn’t have any data on other potential exposure to fluoride.
Takeaway Message
This study provides some of the first large-scale, long-term, U.S.-based data on the cognitive effects of fluoride exposure—a combination that should be relevant for current and future discussions of water fluoridation.
Related Information
Source
John Robert Warren, et al. Municipal water fluoridation, adolescent IQ, and cognition across the life course: evidence from the Wisconsin Longitudinal Study. PNAS. Published April 13, 2026. doi: 10.1073/pnas.2536005123
(Image: Getty Images/iStock/Kemal Yildirim)
