The British Regional Heart Study: cardiovascular mortality and water quality.

The Regional Heart Study aims at determining the factors responsible for the marked regional variations in coronary heart disease and stroke in Great Britain. This report is concerned with mortality (1969-1973) from cardiovascular disease in 253 towns in England, Wales and Scotland with particular reference to water quality (hardness), climate, air pollution, socio-economic and genetic (blood group) factors. The preliminary results reaffirm an association between water hardness and cardiovascular (CV) mortality, with towns with soft water tending to have hgiher CV death rates than towns with hard water. Multiple regression analysis shows that this relationship is somewhat weakened after allowing for rainfall, temperature and socio-economic factors but that it remains statistically significant for both coronary heart disease and stroke. A study of 13 towns with artificially softened water supplies indicates that their CV mortality is no higher than in neighbouring towns without softened water. A study of the prevalence of risk factors for cardiovascular disease is being carried out in 25 British towns selected to represent all the variations in CV mortality and water hardness and representing all major geographic regions of Britain. The incidence of CV disease in the 7,500 men aged 40-59 years in this study will be related to personal and environmental risk factors. Preliminary data show an association between mean blood pressure levels and CVD mortality rates.