Cerebrovascular disease mortality rates and water hardness in North Dakota.

Geographic clustering of high and low cerebrovascular disease mortality rates is evident within North Dakota. It was hypothesized that this distribution might be related to geographic variations in drinking water hardness. Correlation analysis indicated that associations between cerebrovascular disease death rates and several drinking water constituents were weak. Although some weak relationships exist, it does not appear that the water factor can adequately account for the spatial pattern of cerebrovascular disease in North Dakota.