Dietary Magnesium and the Risk of Stroke among Women

Abstract
Background: Epidemiology studies suggest that high magnesium intake may decrease the risk of stroke by reducing hypertension, endothelial dysfunction and carotid artery thickness, but the results are inconsistent. We therefore examined the association between magnesium intake and stroke type in a cohort with repeated measurement of diet, long duration of follow up, and a large sample size.

Methods: We prospectively followed 86,149 women in the Nurses’ Health Study, aged 35 to 55 years, who were free of diagnosed cardiovascular disease and cancer at baseline in 1980. Data on dietary intake were collected with a semi-quantitative food frequency questionnaire at baseline in 1980, 1984, 1986 and then every 4 years, while data on stroke, stroke risk factors and potential confounders were collected at baseline and updated biennially. Strokes were classified according to the National Survey of Stroke criteria; and strokes for which medical records were not available were classified as probable/unknown. We calculated the hazard ratio (95% CI) of stroke by quintiles of magnesium intake, using multivariate Cox proportional hazard models, adjusting for potential confounders.

Results: During 28 years of follow-up, 3237 total strokes (1664 ischemic, 544 hemorrhagic and 1029 probable/unknown) were documented. In multivariate analyses adjusting for age, total calories, smoking, body-mass index, parental history of heart disease, alcohol intake, physical activity, menopausal therapy, history of hypertension, hypercholesterolemia and diabetes at baseline, as well as use of multivitamin, aspirin, and thiazides, women in the highest quintile of magnesium intake had a relative risk (RR) of 0.85 (95% CI, 0.72 to 0.96; P for trend=0.03) for total stroke; 0.86 (95% CI, 0.72 to 1.01; P for trend=0.05) for ischemic stroke; and 0.85 (95% CI, 0.62 to 1.08; P for trend=0.37) for hemorrhagic stroke, compared with those in the lowest quintile. Further adjustment for potassium and calcium attenuated these associations; for total stroke the risk estimate was 0.90 (0.75 to 1.06; P for trend=0.38).

Conclusions: Low magnesium intake may contribute to higher risk of stroke, but distinction from potential effects of potassium and calcium is difficult.
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Abstract P223: Dietary Magnesium and the Risk of Stroke among Women
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