Science

Stephanie E. Chiuve, Ethan C. Korngold, James L. Januzzi Jr, Mary Lou Gantzer, and Christine M. Albert

Background: Magnesium has antiarrhythmic properties in cellular
and experimental models; however, its relation to sudden cardiac
death (SCD) risk is unclear.
Objective: We prospectively examined the association between
magnesium, as measured in diet and plasma, and risk of SCD.
Design: The analysis was conducted within the Nurses’ Health
Study. The association for magnesium intake was examined prospectively
in 88,375 women who were free of disease in 1980. Information
on magnesium intake, other nutrients, and lifestyle factors
was updated every 2–4 y through questionnaires, and 505 cases of
sudden or arrhythmic death were documented over 26 y of followup.
For plasma magnesium, a nested case-control analysis including
99 SCD cases and 291 controls matched for age, ethnicity,
smoking, and presence of cardiovascular disease was performed.
Results: After multivariable adjustment for confounders and potential
intermediaries, the relative risk of SCD was significantly lower
in women in the highest quartile compared with those in the lowest
quartile of dietary (relative risk: 0.63; 95% CI: 0.44, 0.91) and
plasma (relative risk: 0.23; 95% CI: 0.09, 0.60) magnesium. The
linear inverse relation with SCD 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% (95% CI:
15%, 58%) lower risk of SCD.
Conclusions: In this prospective cohort of women, higher plasma
concentrations and dietary magnesium intakes were associated with
lower risks of SCD. If the observed association is causal, interventions
directed at increasing dietary or plasma magnesium might
lower the risk of SCD.