Asked by: Earl Baldwin of Bewdley (Crossbench - Excepted Hereditary)
Question to the Department of Health and Social Care:
To ask Her Majesty’s Government, further to the Written Answers on fluoride in drinking water by Lord Prior of Brampton on 21 September (HL1940 and HL2178), what evidential weight they give to ecological analyses which compare health outcomes in a fluoridated area with those in an unfluoridated one.
Answered by Lord Prior of Brampton
Ecological studies are used for comparing public health outcomes in populations. This is particularly so where multiple populations can be included, there can be a proper account of other factors that might have affected the recorded levels of disease and where reasonable assurance that the ascertainment of disease or exposure to a factor under study has been the same for all observed populations.
As such, this study design is appropriate for monitoring health outcomes in fluoridated and non-fluoridated populations. As an example of the caution that should be adopted when observing differences between fluoridated and non-fluoridated populations, the authors of the 2014 Public Health England (PHE) health monitoring report, both in the report and in a recent summary in the scientific literature (Young et. al. 2015 which is attached) stressed that, whilst lower levels of renal stones and bladder cancer were observed in fluoridated populations, the ecological design prohibits any conclusions being drawn about a protective role of water fluoridation for these conditions.
Asked by: Earl Baldwin of Bewdley (Crossbench - Excepted Hereditary)
Question to the Department of Health and Social Care:
To ask Her Majesty’s Government what assessment they have made of the statement in the 2015 systematic Cochrane review <i>Water fluoridation for the prevention of dental caries</i> that the authors’ confidence in evaluating fluoridation’s effectiveness was limited by there being "very little contemporary evidence, meeting the review’s inclusion criteria", and by "the high risk of bias within the studies and, importantly, the applicability of the evidence to current lifestyles".
Answered by Lord Prior of Brampton
The results of the 2015 ‘Cochrane Review’ Water fluoridation for the prevention of dental caries’, Iheozor-Ejiofor et al, Feb 2015 are broadly consistent with those from other systematic reviews conducted over the past 15 years in concluding that this public health measure is, as the Cochrane authors state, “effective at reducing levels of tooth decay in both children’s baby and permanent teeth.”
The Cochrane review used specific and relatively narrow criteria requiring that studies include baseline measures of dental caries in two communities, one of which then introduced fluoridation within three years. This approach had the consequence of excluding numerous studies conducted over the past 25 years which compared dental caries levels in fluoridated and non-fluoridated communities. The Cochrane reviewers acknowledge in their report that there may be concerns regarding the exclusion of these studies from their review.
The Cochrane review analysed studies conducted in different ways at different times in different places, finding consistent reductions in levels of dental caries following the introduction of fluoridation. The term ‘bias’ used in the Cochrane review has a specific scientific meaning relating to controlling for other factors such as dietary habits that might have affected the levels of dental caries in the populations studied. The reviewers recognise that this bias “may occur in either direction”.
Relatively recent studies which did not meet the reviewer’s specific inclusion criteria have continued to find substantial dental benefits of water fluoridation. Public Health England’s (PHE) recent Monitoring Report (2014) looked at fluoridated and non-fluoridated communities in England and found that communities served by water fluoridation schemes continue to show lower levels of tooth decay.
A copy of PHE’s report is attached.