Magnesium and calcium in drinking water and acute myocardial infarction

Abstract

Objectives: Several studies have shown an inverse relation between mortality from ischemic heart disease and water hardness. The objectives of this thesis were to evaluate the relation between the main determinants of water hardness - magnesium and calcium - and the mortality and morbidity from acute myocardial infarction and to investigate the importance of water magnesium for body magnesium status.Methods: In the first study, water data were collected from 27 municipalities in Sweden and related to the age-adjusted mortality ratio from ischemic heart and cerebrovascular disease during the period 1969-1978. In two studies, the relation between death from acute myocardial infarction (AMI) and the level of magnesium and calcium in drinking water was examined on the individual level in men (n=1843) and women (n=1746) using mortality registers and a case-control design. In the fourth study, the importance of magnesium in drinking water for fatal and nonfatal acute myocardial infarction was investigated in a prospective case-control study. Individual water data were collected for all cases and controls, and interviews were conducted with surviving cases (n=823) and population controls (n=853) focusing on risk factors for AMI. Finally, body magnesium was measured using an oral loading test among subjects who changed from drinking water with a low magnesium concentration (1.6 mg/l) to water with a higher concentration (25 mg/l). Results: An inverse relation was found between magnesium in drinking water and death from AMI. The odds ratios for the quartile with the highest magnesium levels (above 9-10 mg/l) ranged between 0.64 and 0.70 in the studies. However, no relation was found between magnesium in drinking water and the total incidence of acute myocardial infarction. It was mainly the number of deaths occurring outside hospitals that was lower with higher magnesium levels. Calcium in drinking water had a weaker impact and was important mainly in women. Other risk factors for myocardial infarction did not influence the results in multivariate analyses and were thus not confounding factors. After six weeks of supplementation with magnesium-enriched water, the body magnesium content was significantly increased.