Abstract P402: Serum Magnesium and the Risk of Ischemic Stroke among Women

Abstract

Background: Low magnesium levels may be associated with higher blood pressure as well as endothelial dysfunction. Results from studies examining the association between serum magnesium and risk of stroke are inconsistent, with some studies suggesting a protective association with higher levels. Methods: Among 32,826 participants in the Nurses’ Health Study who provided blood samples in 1989-1990, ischemic strokes were identified and confirmed by medical records through 2006. We conducted a nested case-control analysis of 460 cases, matched to controls (1:1) on age, menopausal status, use of postmenopausal hormones, ancestry, date of blood draw, fasting status and smoking status. Magnesium quintiles were created based on the distribution of serum magnesium levels among controls, and a dichotomous variable was also created, based on prior data: low magnesium (<2.0 mg/dL) and high magnesium (≥ 2.0 mg/dL). Conditional logistic regression models were used to estimate the multivariable adjusted association of serum magnesium and the risk of ischemic stroke and unconditional analyses were used to assess effect modification. Results: In univariate analysis, median magnesium levels did not differ between stroke cases and controls (median=2.1 in each, p-value=0.16). Conditional on matching factors, women in the lowest magnesium quintile had a relative risk (RR) of 1.34 (95% confidence interval [CI]: 0.85-2.09) for ischemic stroke, compared to those in the highest quintile. Additional adjustment for potential confounders (alcohol intake, body mass index [BMI], physical activity, aspirin use, thiazide diuretic use, history of diabetes, history of coronary heart disease, glycosylated hemoglobin and the ratio of total to HDL-cholesterol) did not substantially alter the risk estimates (RR=1.34; 95% CI: 0.82-2.17). However, women with magnesium levels <2.0mg/dL had a significant increase in the risk of ischemic stroke, compared to women with magnesium levels ≥2.0 (RR= 1.66; 95% CI: 1.18 - 2.34. Controlling for potential confounders (as above) did not significantly alter this risk (RR= 1.63; 95% CI: 1.13 - 2.36). No significant effect modification was observed by age, BMI, hypertension or diabetes. Conclusions: Serum magnesium levels <2.0 are associated with increased risk of ischemic stroke among this population of women.