A new multi-country water hardness and health outcome study is being initiated 21-22 January 2008
Introduction
A 2006 WHO expert meeting reviewed the possible protective effect of hard water against cardiovascular disease, and recommended further studies to examine health outcomes in populations that had experienced a change in the hardness of their drinking water supply. In response, WHO will be convening a meeting 21-22 January 2008 to kick-start a coordinated (i.e common protocol) multi-country study, and is inviting participants who would be interested in initiating individual country studies. Note WHO is not providing funding support for the country studies themselves.
Summary
A large volume of literature has been generated examining the possible association between drinking water hardness and various health outcomes over a fifty year period. In April 2006, the WHO organised an expert meeting to review the possible protective effect of hard water against cardiovascular disease. A key recommendation arising from this was the need to examine possible alterations in health outcomes in populations that had experienced a notable change in the hardness of their drinking water supply. To this end, WHO will coordinate international work to investigate step changes in community drinking water hardness, calcium or magnesium and possible associated health outcomes. To support this process, WHO will be convening a meeting to establish a harmonized internationally study protocol so that results can be pooled and analysed. To kick start-this process, the United Kingdom has agreed to provide a draft protocol for discussion which has been already implemented, to examine this issue in detail in England and Wales. WHO is now inviting expressions of interest from countries to be involved in such a study and who would be interested in attending the above-mentioned meeting.
Background and rationale
Approximately 50 years ago, the first papers were published suggesting an inverse association between drinking water hardness and cardiovascular mortality. Since that time, a large number of studies investigating this general association have been published from many different nations. However, the basic question of whether or not the consumption of hard water protects against death from cardiovascular disease is still debated.
An impetus for a reconsideration of this issue includes modern developments such as the increased usage of desalinised water for drinking water consumption and the potential for the modification of mineral content. There is recognition that if the inverse association between drinking water hardness and cardiovascular health is causal, there are widespread public health implications.
Expert meeting and knowledge gaps
A recent systematic review of studies examining aspects of drinking water hardness and cardiovascular disease concluded that a comparatively small proportion of the published studies were of high quality, but there was evidence to support a protective effect. Following presentation of this review at the International Symposium of Health Aspects of Calcium and Magnesium in Drinking Water held in Baltimore (April 2006)., a WHO expert working group accepted that there was evidence in favour of the water hardness hypothesis in general, and magnesium concentrations in particular. However the evidence was not considered to be definitive, and a number of knowledge gaps and areas requiring research were identified.
A key recommendation arising from the expert meeting was the need for more well designed epidemiological studies to elucidate the health implications of waterborne calcium and magnesium. Within this remit came a recommendation for ‘community intervention studies’, whereby communities that had experienced a notable change in drinking water parameter concentrations were examined for corresponding changes in health outcomes.
United Kingdom - example study
Within England and Wales, provision of public drinking water is through a number of private water supply companies who are regulated by the Drinking Water Inspectorate (DWI). In collaboration with the DWI, investigators from the University of East Anglia contacted each company to establish if there had been any notable changes in the hardness of the drinking water supplied to any communities within their supply area. Typical reasons for a notable change in the hardness included a change of source water or introduction/cessation of a softening practice. Anonymised individual level mortality data were obtained from the Office of National Statistics including gender, age at death, date of death, cause of death and postcode of last residence. The postcode allowed investigators to obtain a geographic reference for each individual thus enabling the identification of all mortality cases occurring within the study areas.
In brief, once an area of change had been identified GIS software was used to delineate the area and identify all mortality cases occurring in that area. Mortality data were collected for all causes and also for selected cardiovascular causes of death. Deaths were further collated by gender and age subgroups. Trends in the mortality time series were then examined for any notable response to the intervention indicator, i.e. the time of change in the drinking water hardness parameters. The proposal also incorporates the possibility of examining the magnitude of effect against relative changes and concentrations.
Call for participation
WHO is inviting expressions of interest from interested countries that wish to commence studies, replicating the agreed protocol. WHO will then pool and analyse the data in order to arrive at a definite conclusion on the relationship between drinking water hardness and cardiovascular health.
As a first step, WHO will be convening a meeting on 21-22 January 2008 to kick-start a coordinated (i.e. common protocol) multi-country study, and is inviting participants who would be interested in initiating individual country studies. Note: WHO is not providing funding support for the country studies themselves.
Expressions of interest should be directed towards Paul Hunter, University of East Anglia, with a copy to Penny Ward, World Health Organization, Geneva, who has been commissioned by WHO to support preparations for this cooperative international study.
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