Magnesium Reduces Cardiac Death Risk

BOSTONWomen with higher dietary magnesium intakes and blood levels are less likely to die from sudden heart failure, according to a new study from Harvard Medical School (Am J Clin Nutr Nov. 2010 ajcn.002253. DOI: 10.3945/ajcn.110.002253). Women who had the most magnesium in their diets were significantly less like to die from heart failure than those who ate the least, and each 0.25-mg/dL increment of magnesium blood concentration was associated with a 41-percent lower risk of sudden cardiac death.

Harvard researchers, led by Stephanie E. Chiuve, examined the association for magnesium intake in 88,375 women within the Nurses' Health Study who were free of disease in 1980. Information on magnesium intake, other nutrients and lifestyle factors was updated every 2 to 4 years through questionnaires. During 26 years of follow-up, 505 cases of sudden or arrhythmic death were documented. For plasma magnesium, a nested case-control analysis including 99 sudden cardiac death cases and 291 controls matched for age, ethnicity, smoking and presence of cardiovascular disease (CVD) was performed.

The relative risk of sudden cardiac death was significantly lower in women in the highest quartile compared with those in the lowest quartile of dietary (relative risk: 0.63; 95 percent CI: 0.44, 0.91) and plasma (relative risk: 0.23; 95 percent CI: 0.09, 0.60) magnesium, even after multivariable adjustment for confounders and potential intermediaries. The linear inverse relation with sudden cardiac death was strongest for plasma magnesium (P for trend = 0.003), in which each 0.25-mg/dL (1 SD) increment in plasma magnesium was associated with a 41-percent (95 percent CI: 15, 58 percent) lower risk of sudden cardiac death.

The study was supported by a research grant from Siemens Healthcare Diagnostics, an Established Investigator Award from the American Heart Association to CMA and grants from the National Institutes of Health.