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.
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.