Abstract

Investigations conducted in several parts of the world have shown that residents of soft-water areas have a higher death rate from ischemic heart disease than residents of hard-water areas. The same pattern appears to exist in Ontario, but when deaths are divided into sudden and nonsudden (on the basis of whether or not the death certificate was signed by a coroner), the higher death rate in the soft-water areas is found to be due entirely to an excess of sudden deaths. This finding suggests that the correlation between cardiac mortality and water hardness may be the result of an increased susceptibility to lethal arrhythmias among residents of soft-water areas.