Changes in water hardness and cardiovascular death rates.

Ten years ago Crawford, Gardner and Morris reported that changes in cardiovascular death rates between 1951 and 1961 had been associated with changes in the hardness of water supplies. That study has been critically reviewed but after amendments to method and data its overall conclusion is upheld. New results based on changes that have taken place in water hardness and in cardiovascular death rates between 1961 and 1971 in the county boroughs of England and Wales indicate a significant trend for men, in the direction of decreasing cardiovascular mortality with increasing hardness, but no trend for women. The trend in male mortality appears to be specific to cardiovascular disease. The results are similar to those of the earlier study and support the hypothesis of a weak causal relationship between the hardness of drinking water and mortality from cardiovascular disease.