Long-Term Study Finds No Link Between Water Fluoridation and Cognitive Decline

For decades, fluoride has been added to public drinking water worldwide to reduce tooth decay, a practice considered a major public health success. However, recent debates have questioned whether fluoride exposure might also affect brain development and cognitive function. A new long-term study based on data from over 10,000 individuals in Wisconsin, USA, found no evidence that water fluoridation at levels typical in the United States is associated with lower cognitive abilities.

The study tracked participants who graduated high school in 1957, comparing those who grew up in areas with fluoridated water to those without. Researchers assessed IQ scores during adolescence and conducted repeated cognitive tests, including memory evaluations, up to age 80. The findings showed no link between fluoridated water exposure and reduced IQ, memory impairment, or other cognitive declines over the lifespan.

Fluoride naturally occurs in rocks, soil, and water and strengthens tooth enamel by aiding natural repair processes, thereby preventing cavities. While excessive fluoride can cause dental fluorosis, discoloration of teeth, the controlled addition of fluoride to water supplies aims to balance benefits and risks. The World Health Organization recommends fluoride concentrations in drinking water not exceed 1.5 mg per liter to avoid adverse effects, with typical artificial fluoridation levels ranging from 0.5 to 1 mg per liter.

The new study's strength lies in its extensive follow-up period and large sample size, though it did not measure individual fluoride exposure directly, relying instead on residential history and regional fluoridation records. It also lacked data on other fluoride sources like toothpaste or diet. Importantly, participants were exposed to fluoride levels common in public water systems, not the higher natural concentrations sometimes linked to cognitive concerns.

In Israel, the fluoridation debate has gained new relevance due to widespread use of desalinated water, which contains less natural fluoride. Although fluoridation was discontinued in 2014, health authorities have expressed support for its reinstatement, but it has yet to resume. This study adds to the body of evidence suggesting that fluoridation at recommended levels does not negatively impact cognitive development, though the broader discussion continues globally.