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To explain the associations of water hardness and air temperature with area differences in ischaemic heart disease mortality, samples of tap water were obtained from homes in 61 county boroughs in England and Wales, and the concentration of calcium and 12 other elements was estimated. Multiple regressions were calculated with the death rates from various causes as dependent variables and with the concentration of the elements in the tap water, mean annual temperature, mean annual rainfall, and a socioeconomic index as independent variables. The well known negative association between water hardness and ischaemic heart disease was shown to be due to calcium, and none of 12 other elements examined appeared to contribute significantly to the association. Area differences in other causes of death also showed an association with calcium. There was little association between temperature and ischaemic heart disease.
Elwood et al. (Thu,) studied this question.
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