Background:
Plasma magnesium (Mg) has been strongly associated with lower risk of fatal coronary heart disease (CHD) and sudden cardiac death, which may be due to its anti-arrhythmic properties. Mg also affects endothelial function, inflammation, blood pressure and diabetes and thus may impact atherosclerosis in general. We examined the association between magnesium, measured in diet and plasma, and risk of fatal, nonfatal and total CHD among women in the Nurses’ Health Study.
Design:
The association for Mg intake was examined prospectively among 86,361 women free of disease in 1980. Mg intake and other covariates were ascertained updated every 2-4 years through questionnaires and 3661 cases of CHD (1214 fatal/2447 nonfatal) were documented through 2008. For plasma Mg, we conducted a nested case-control analysis with 405 CHD (63 fatal/342 nonfatal) cases, matched to controls (1:1) on age, smoking, fasting status, and date of blood sampling.
Results:
Dietary magnesium was inversely associated with risk of CHD, even after controlling for diet and CHD risk factors (RR comparing extreme quintiles: 0.75; 95%CI: 0.64, 0.89;
P
trend=0.002) (Table 1). The relationship with plasma Mg was less linear (
P
trend=0.09) with a potential threshold effect at the 2
nd
quintile. The RR of CHD comparing plasma Mg >2.0 v. ≤2.0 mg/dl was 0.49 (95%CI: 0.32, 0.74). The associations for dietary and plasma Mg appeared stronger for fatal versus nonfatal CHD. The RR (95%CI;
P
trend) comparing the highest to lowest quintile of dietary Mg was 0.60 (0.45, 0.79;
p
<0.001) for fatal and 0.85 (0.70, 1.04;
p
= 0.14) for nonfatal CHD. The RR (95%CI) comparing plasma Mg >2.0 v. ≤2.0 mg/dl was 0.23 (0.07, 0.81) for fatal and 0.55 (0.35, 0.86) for nonfatal CHD.
Conclusions:
Higher levels of Mg, in diet and plasma, were associated with lower risk of total CHD among women. The consistent inverse association found between two measures of Mg and CHD risk supports the hypothesis that Mg might lower CHD risk through multiple mechanisms, and may be most strongly protective for fatal events.
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