Magnesium in drinking water in relation to morbidity and mortality from acute myocardial infarction

We investigated the importance of magnesium and calcium in drinking water i n relation to morbidity and mortality from acute myocardial infarction. Cas es were men and women 50-74 years of age living in 18 Swedish municipalitie s who had suffered an acute myocardial infarction some time between October 1, 1994, and June 30, 1996. Controls were randomly selected from the same study base. We interviewed the surviving cases (N = 823) and controls (N = 853), focusing on risk factors for acute myocardial infarction. We collecte d individual data on drinking water levels of magnesium and calcium. We cla ssified subjects by quartile of water magnesium or calcium levels. The tota l number of cases was similar in the four quartiles. The risk of death was 7.6% (95% confidence interval = 2.1-13.1) Lower in the quartile with high m agnesium levels (greater than or equal to 8.3 mg/liter). The odds ratio for death from acute myocardial infarction in relation to water magnesium was 0.64 (95% confidence interval = 0.42-0.97) for the highest quartile relativ e to the three loser ones. Multivariate analyses showed that other risk fac tors were not important confounders. For calcium, this study was inconclusi ve. The data suggest that magnesium in drinking water is associated with lo wer mortality from acute myocardial infarction, but not with the total inci dence.