Fluoride Study Reveals Lifetime Exposure Has No Cognitive Link
An Irish study of about 2,500 older adults found no link between decades of fluoridated drinking water and poorer cognitive function. Trinity College Dublin researchers published the findings in the Journal of Dental Research, though they note limits for early-life exposure.
A new Irish study reveals lifetime exposure to fluoridated drinking water is not associated with poorer cognitive function in older adults, according to research published in the Journal of Dental Research.
The finding bears on a long-running public argument. Utah and Florida became the first US states to ban water fluoridation last year, citing concerns about possible harm.
What the researchers did
Researchers analyzed data from the Irish Longitudinal Study on Ageing (TILDA). They examined roughly 2,500 older adults with an average age of 65, whose exposure to fluoridated water could be traced across at least 50 years of their lives.
Ireland introduced nationwide water fluoridation in 1964. Fluoride concentrations in local supplies varied, so participants' exposure depended on where they had lived.
The team sorted participants into low-, medium- and high-exposure groups by residential location. They then compared those groups against results from two different cognitive assessments. They found no link between fluoride exposure and cognitive performance.
What the authors said
"Our findings provide reassurance that lifetime exposure to fluoridated drinking water at the levels used in Ireland is not associated with poorer cognitive function in older adults," said lead author Vinay Sharma, a public health researcher at Trinity College Dublin.
Sharma added that the team hopes the results "contribute to an evidence-based conversation about the safety of the community water fluoridation program in Ireland and internationally."
Michael Crowe, a dental researcher at Trinity College Dublin, said fluoridation has been "one of the most effective tools we have for reducing tooth decay at a population level." He said it matters that there is now long-term Irish evidence "that it isn't costing anything in terms of cognitive health."
Limits of the findings
A subset of the youngest participants had been exposed to fluoridated water in their first five years of life. That early exposure also showed no association with cognitive performance.
Only 5 percent of the sample, or 124 people, had early-life exposure. The researchers say that limits how firmly they can draw conclusions on that point.
A finding of no link does not prove fluoride is harmless to the brain. It shows only that evidence of harm was not found in this group.
Other research
The results match earlier studies that also detected no link between fluoridated drinking water and cognitive function.
Not all research agrees. Two studies in China linked fluoride to cognitive impairment in elderly people, but those findings related to excessive fluoride exposure, known as fluorosis, and are not directly comparable.
A 2025 meta-analysis linked fluoride to lower IQ scores in children. Some of that evidence involved concentrations higher than those normally used in water fluoridation.
