Prospective Study of Calcium, Potassium, and Magnesium Intake and Risk of Stroke in Women

Abstract

Background and Purpose-High intakes of calcium, potassium, and magnesium have been hypothesized to reduce risks of cardiovascular disease, but only a few prospective studies have examined intakes of these cations in relation to risk of stroke. Methods-In 1980, 85 764 women in the Nurses' Health Study cohort, aged 34 to 59 years and free of diagnosed cardiovascular disease and cancer, completed dietary questionnaires from which we calculated intakes of calcium, potassium, and magnesium. By 1994, after 1.16 million person-years of follow-up, 690 incident strokes (129 subarachnoid hemorrhages, 74 intraparenchymal hemorrhages, 386 ischemic strokes, and 101 strokes of undetermined type) had been documented. Results-Intakes of calcium, potassium, and magnesium were each inversely associated with age-and smoking-adjusted relative risks of ischemic stroke, excluding embolic infarction of nonatherogenic origin (nϭ347). Adjustment for other cardiovascular risk factors, including history of hypertension, attenuated these associations, particularly for magnesium intake. In a multivariate analysis, women in the highest quintile of calcium intake had an adjusted relative risk of ischemic stroke of 0.69 (95% CI, 0.50 to 0.95; P for trendϭ0.03) compared with those in the lowest quintile; for potassium intake the corresponding relative risk was 0.72 (95% CI, 0.51 to 1.01; P for trendϭ0.10). Further simultaneous adjustment for calcium and potassium intake suggested an independent association for calcium intake. The association of risk with calcium intake did not appear to be log linear; the increase in risk was limited to the lowest quintile of intake, and intakes ϾϷ600 mg/d did not appear to reduce risk of stroke further. The inverse association with calcium intake was stronger for dairy than for nondairy calcium intake. Intakes of calcium, potassium, and magnesium were not related to risk of other stroke subtypes. Conclusions-Low calcium intake, and perhaps low potassium intake, may contribute to increased risk of ischemic stroke in middle-aged American women. It remains possible that women in the lowest quintile of calcium intake had unknown characteristics that made them susceptible to ischemic stroke. (Stroke. 1999;30:1772-1779.)

Dairy Consumption and Risk of Stroke: A Systematic Review and Updated Dose–Response Meta‐Analysis of Prospective Cohort Studies

“…Table 1 shows the characteristics of the 18 prospective cohort studies11, 15, 16, 17, 19, 20, 21, 22, 23, 24, 25, 28, 29, 30, 31, 32, 33 including 1 case‐cohort study,29 which comprised 762 414 participants and 29 943 stroke events. Two studies presented sex‐specific results,19, 29 2 comprised only women,17, 28 and 3 only men 20, 30, 32.…”

“…In case of duplicate results,26, 27 we included the most updated23 or comprehensive27 results. For the Nurses’ Health Study we used 2 articles: 1 on low‐fat and high‐fat dairy23 and 1 on other types of dairy 28. One article provided results for 2 studies (Nurses’ Health Study and the Health Professionals Follow up Study)23 and 2 presented results for men and women separately,19, 29 resulting in 18 studies (see flow chart in Figure 1).…”

“…One article provided results for 2 studies (Nurses’ Health Study and the Health Professionals Follow up Study)23 and 2 presented results for men and women separately,19, 29 resulting in 18 studies (see flow chart in Figure 1). 11, 14, 15, 16, 17, 19, 20, 21, 22, 23, 24, 25, 28, 29, 30, 31, 32, 33 …”

“…If dairy intake was only reported in portions,11, 23, 28, 31, 33 we used portion sizes of 177 g for total, low‐fat, and high‐fat dairy; 244 g for total, low‐fat, and high‐fat milk; 244 g for yogurt; and 43 g for cheese to estimate grams per day34, 35 or we used previously reported serving sizes of the same cohort 23, 28. For open‐ended upper limits of intake, we applied the same width as the adjacent category, whereas for open‐ended lowest categories a zero was assigned.…”

“…For the meta‐analysis on fermented dairy we included studies that combined at least 2 of the products cheese, yogurt, and sour milk. If results on total stroke (primary outcome) were not available, we used ischemic stroke 17, 28. Two reviewers (J.G.…”