Relationship between Hardness and Silicic Acid in Drinking Water with Cerebrovascular Disease Mortality Rates in Okinawa Prefecture, Japan

Abstract

Environmental weather and dietary life exist within the same aspect throughout the Okinawa Prefecture. However on the farming population rates and the nature of drinking water there were regional differences. The correlations between above factors and the mortality from cerebro-vascular disease (CVD) were investigated. Interrelationships between CVD and several trace elements in drinking water were found to be strong and complex, especially water hardness and silicon seemed to make an important contribution to mortality from CVD. The mortality from CVD indicated the highest negative correlation coefficient (r=-0.86) for drinking water hardness. In our research regions, silicon concentration in drinking water was lower levels (6-14 mg/l) in Japan and correlated negatively with the mortality from CVD (r=-0.76). On the correlation with mortality from CVD, silicon concentration is considered to have a threshold value, which is presumed to about 10 mg/l. The mortality from CVD and farming population rate showed positive correlation (r=0.75). The mortality rate and Ca²⁺/SO₄^-2 are represented as the negative correlation.