Potassium, Calcium, and Magnesium Intakes and Risk of Stroke in Women

Susanna C. Larsson; Jarmo Virtamo; Alicja Wolk

Disclosures

Am J Epidemiol. 2011;174(1):35-43. 

In This Article

Results

Among the 34,670 women, who were followed for a mean of 10.4 years, we ascertained 1,680 incident stroke events, including 1,310 cerebral infarctions, 154 intracerebral hemorrhages, 79 subarachnoid hemorrhages, and 137 unspecified strokes. Baseline characteristics of the study population according to intakes of potassium, calcium, and magnesium are shown in Table 1. Potassium intake was strongly positively correlated with magnesium intake (r = 0.81) and weakly correlated with calcium intake (r = 0.15). Intakes of calcium and magnesium were weakly positively correlated (r = 0.20).

We observed no overall association between dietary intakes of potassium, calcium, and magnesium and risk of total stroke or cerebral infarction after adjustment for other risk factors (Table 2). Results were similar when potassium, calcium, and magnesium were included in the same multivariable model. Excluding women who reported use of dietary supplements containing calcium or magnesium (including multivitamins with minerals) did not change the results appreciably. After excluding supplement users, the multivariable relative risks of total stroke for the highest quintile of intake compared with the lowest were 0.92 (95% confidence interval (CI): 0.74, 1.14) for calcium and 0.94 (95% CI: 0.75, 1.19) for magnesium (data not shown). Excluding women with a low body mass index (<15) did not change the results (data not shown).

We examined more extreme intakes of the minerals by categorizing women into deciles of potassium, calcium, and magnesium intakes. Compared with women in the lowest decile of intake, the multivariable relative risks of total stroke for those in the highest decile were 0.71 (95% CI: 0.54, 0.94) for potassium, 1.17 (95% CI: 0.92, 1.50) for calcium, and 0.85 (95% CI: 0.64, 1.12) for magnesium.

Calcium intake was positively associated with risk of intracerebral hemorrhage (relative risk for the highest tertile (vs. lowest) = 2.04, 95% confidence interval: 1.24, 3.35) (Table 3). There was no association between potassium or magnesium intake and risk of intracerebral hemorrhage or subarachnoid hemorrhage.

Because hypertension is an important risk factor for stroke, we performed analyses stratified by history of hypertension at baseline (Table 4). Potassium intake was statistically significantly inversely associated with risk of total stroke and cerebral infarction among women with a history of hypertension but not among women with no history of hypertension. There was a suggestion of an interaction between potassium intake and history of hypertension in relation to the risk of cerebral infarction (P = 0.07) but not of total stroke (P = 0.26). We also observed a statistically significant inverse association between magnesium intake and the risk of cerebral infarction among women with a history of hypertension, but no association was observed among those without hypertension. There was a statistically significant interaction between magnesium intake and hypertension in relation to risk of cerebral infarction (P = 0.03). The association between calcium intake and stroke risk did not vary significantly by stratum of hypertension.

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