New research led by a public health expert at the University of Kent suggests water fluoridation in England is linked to higher rates of underactive thyroid.
Professor Stephen Peckham, of the University’s Centre for Health Service Studies, says a switch to other approaches to protecting tooth health should be considered.
In research published in the Journal of Epidemiology & Community Health, Professor Peckham and the research team identified that water fluoridation above a certain level is linked to 30 per cent higher than expected rate of underactive thyroid (hypothyroidism) in England.
The researchers looked at the 2012 levels of fluoride in the drinking water supply, using data provided by the Drinking Water Inspectorate for individual postcodes. They looked at the national prevalence of underactive thyroid diagnosed by family doctors in England in 2012-13 and recorded in their national quality and incentive scheme (QOF) returns. Complete data were provided for 7935 general practices out of a total of 8020.
The researchers also carried out a secondary analysis, comparing two built up areas, one of which (West Midlands) was supplied with fluoridated drinking water, and the other of which (Greater Manchester) was not.
After taking account of influential factors, such as female sex and older age, both of which are linked to increased risk of hypothyroidism, they found an association between rates of the condition and levels of fluoride in the drinking water. In areas with fluoride levels above 0.7mg/l, they found higher than expected rates of hypothyroidism than in areas with levels below this dilution.
High rates of hypothyroidism were at least 30% more likely in practices located in areas with fluoride levels in excess of 0.3mg/l. And practices in the West Midlands were nearly twice as likely to report high rates of hypothyroidism as those in Greater Manchester.
In England, around 10% of the population (6 million) live in areas with a naturally or artificially fluoridated water supply of 1mg fluoride per litre of drinking water.
Professor Peckham said that research was ‘observational’, so no definitive conclusions should be drawn about cause and effect. He also emphasised that the researchers were not able to take account of other sources of fluoride, often found in dental products and food and drink.
But he pointed out that the findings echo those of previous research and that while they were only able to look at diagnosed hypothyroidism, there might also be other cases of impaired thyroid function that have not yet been diagnosed - and treated.
Professor Peckham concluded that consideration needs to be given to reducing fluoride exposure. Public dental health interventions should ‘stop those reliant on ingested fluoride and switch to topical fluoride-based and non-fluoride-based interventions’, he said.
The research is published in the latest issue of the Journal of Epidemiology & Community Health, which is the official journal of the Society of Social Medicine. See here for the research: http://jech.bmj.com/lookup/doi/10.1136/jech-2014-204971
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Note to editors
The Centre for Health Service Studies (CHSS) is a centre of research excellence that undertakes a wide range of health services research including clinical trials, research on the organisation and delivery of services, survey work, rapid evidence reviews and service evaluations and provides the NIHR Research Design Service in Kent. CHSS has particular methodological expertise in quantitative methods and service evaluation. CHSS has extensive experience of working collaboratively with healthcare staff and organisations. For more information see our website http://www.kent.ac.uk/chss
The University of Kent – the UK’s European university – was established at Canterbury in 1965. It has almost 20,000 students and operates campuses or study centres at Canterbury, Medway, Tonbridge, Brussels, Paris, Athens and Rome. It has long-standing partnerships with more than 100 major European universities and many others across the world, including institutions in Argentina, China, Japan, USA, Canada, Malaysia and Peru.
Kent is one of the few universities to be consistently rated by its own students as one of the best in the UK for the quality of its teaching and academic provision. This includes its position amongst the top 10 multi-faculty universities for overall satisfaction in the 2013 National Student Survey, positioning it within a select band of institutions that have achieved an overall satisfaction rate of 90% and above. It was also ranked 20th in the 2014 Guardian University Guide, 28th in the Sunday Times University League Table 2013, and 28th in the Complete University Guide 2014.
In the 2008 Research Assessment Exercise, Kent placed 24th out of 159 participating institutions in the UK for its world-leading research, while 97% of its academic staff work in schools or centres where the research is rated as either internationally or nationally excellent.
It is worth £0.6 billion to the economy of the South East, with its students contributing £211 million to that total. The University also supports directly or indirectly almost 6,800 jobs in the South East (source: Viewforth Consulting, 2009-10).
In 2012, Kent launched a campaign to celebrate its 50th anniversary.