No link between fluoridated water and cognitive decline in older adults, finds Trinity study

THERE IS NO link between fluoridated water and cognitive decline in older Irish adults, new research from Trinity College Dublin has shown.

The research also found no evidence that exposure in early childhood had any impact.

Community water fluoridation (CWF) was introduced in Ireland in 1964 as a public health measure to prevent tooth decay.

While it has proven effective at this, there has been growing public debate in recent years about whether fluoride could have a negative effect on brain health and development.

The researchers used data from the Irish Longitudinal Study on Ageing (TILDA) to calculate how much fluoride older adults, with an average age of 65, had likely consumed from drinking fluoridated water over their lifetime.

Researchers tracked where they had lived and matched this to national water fluoride concentration records going back many years, down to infancy in some cases. 

Participants were grouped by how much of their lives had been spent drinking fluoridated water, from low to high exposure, and were given two standard cognitive tests used in dementia research.

Scores did not differ between any of the exposure groups, suggesting no link between CWF and cognition in older adults.

Dr Vinay Sharma, from Trinity’s School of Medicine, said the 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”.

The study has been published in the Journal of Dental Research.

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Sharma expressed hope that the findings would “contribute to an evidence-based conversation about the safety of the community water fluoridation programme in Ireland and internationally”.

He added that most previous studies only looked at fluoride exposure over a short window, either in childhood or in adulthood, rather than tracking it continuously across a person’s life and then testing cognitive function later on.

“That’s what sets this study apart,” explained Sharma.

Meanwhile, Trinity professor Lina Zgaga, the principal investigator of the study, noted that Ireland is “unusual because it has a national policy of community water fluoridation”.

She said this “created an opportunity to do high-quality research in large studies and answer many outstanding questions around fluoridation”.

Co-principal investigator Dr Michael Crowe added: “Fluoridation has been one of the most effective tools we have for reducing tooth decay at a population level, so it matters that we now have long-term Irish evidence that it isn’t costing anything in terms of cognitive health.”

The researchers meanwhile said the findings, combined with the established dental health benefits of fluoridation for children and adults, support the continued use of CWF as a public health intervention.

“Nonetheless, we should continue to check for any adverse effects of water fluoridation in the Irish population on an ongoing basis,” said professor Brian O’Connell, another co-author of the research.

“This research establishes a way to monitor the health of water consumers but should just be the baseline for future studies,” he added.

Meanwhile, the researchers noted that one limitation to the study was that it focused on household water fluoride concentration, while there are other factors that contribute to the total amount of fluoride a person ingests.

The researchers also highlighted that the study’s ability to detect any effect of early-life exposure was limited.

This is because only 5% of participants had been exposed to fluoridated water in early childhood – the fluoridation programme began in 1964, so many participants were already older than five by the time it started in Ireland.