For diuretic users, low potassium may increase risk of stroke
Diuretics are regularly prescribed to treat high blood pressure—a strong risk factor for stroke. But, diuretics tend to deplete the body of potassium. Because research suggests that low blood levels of potassium may also increase stroke risk, sorting out the complex relationship between diuretics, potassium levels, and stroke risk is essential. Research published in the August 2002 issue of Neurology suggests that low potassium levels may increase stroke risk, particularly among people taking diuretics.
About the study
Researchers from the Cardiovascular Health Study (CHS) studied 5600 men and women who had participated in the original CHS study from 1989 to 1996. Participants were aged 65 and older when they entered the study and had no history of stroke.
Upon entering the study, participants underwent a complete physical examination and provided information about their medical histories and medication use. They also completed a food frequency questionnaire, which included questions about intake of potassium from food and supplements. In addition, their blood was tested to measure potassium levels, and they underwent several tests to assess heart function. During annual clinic visits and phone interviews every six months, participants were asked to report if they had a stroke. Reported strokes were confirmed via medical records.
For this recent analysis, participants were divided into groups according to their potassium intakes and also according to their blood levels of potassium. Researchers compared the number of strokes among people of varying potassium intakes and blood potassium levels. In addition, they compared risk of stroke between those who took diuretics and those who did not.
Among people taking diuretics, those with low blood levels of potassium were 2.5 times more likely to have a stroke than those with normal blood levels of potassium. Among people not taking diuretics, those with low potassium intakes were 1.5 times more likely to have a stroke than those with normal potassium intakes.
Because diuretics are known to deplete blood levels of potassium, some diuretic users take a potassium supplement. Among diuretic users taking a potassium supplement, those with low blood levels of potassium had a 1.4 times higher stroke risk compared to their counterparts with normal potassium levels. On the other hand, among diuretic users not taking a potassium supplement, those with low blood levels of potassium had a 3.5 times higher stroke risk. What about potassium-sparing diuretics? People taking potassium-sparing diuretics who had low blood levels of potassium were at 2 times higher stroke risk than their counterparts with normal potassium levels.
A particularly high stroke risk was identified in people with atrial fibrillation who were taking diuretics and had low blood levels of potassium. These people were 10 times more likely to have a stroke than their counterparts with normal potassium levels. However, this calculation was based on a very small number of people.
In calculating these statistics, researchers controlled for the following risk factors for stroke: age, sex, race, high blood pressure, diabetes, coronary artery disease, and congestive heart failure.
Although these results seem to identify a clear connection between potassium (intakes or blood levels) and stroke risk, this study has its limitations. First, potassium intake, blood levels of potassium, and blood pressure were only assessed once at the start of the study, which may not reflect actual levels over the seven years of the study. Second, because participants self-reported their potassium intakes, the accuracy of these estimates may have been compromised. Third, this study lacked information on other factors that influence stroke risk, such as smoking and dietary intake of calcium and magnesium. Fourth, in addition to depleting potassium levels, diuretics may also alter blood levels of other electrolytes that affect stroke risk, such as magnesium.
How does this affect you?
Based on these findings, it seems that the amount of potassium in your body affects your stroke risk. However, the precise role of potassium is still unclear. For example, it may be that eating more potassium-rich foods helps reduce stroke risk in people not taking diuretics. But for diuretic users, there doesn’t seem to be an association between dietary intake of potassium and stroke risk. According to the study, it is low blood levels of potassium that are associated with an increased stroke risk among diuretic users.
The more important message from this study is that people taking diuretics to lower their blood pressure ought to pay attention to their blood levels of potassium. However, more research is needed to determine whether taking potassium supplements or eating more potassium-rich foods to balance the potassium loss caused by diuretics will reduce stroke risk. Because high blood pressure is a significant risk factor for stroke and diuretics are so effective at lowering blood pressure, these medications are still considered important for reducing stroke risk. Therefore, it’s particularly important that you not stop taking diuretics without consulting your physician. A great deal more research is needed to determine the role of potassium levels (and other vitamins and minerals) in increasing or decreasing stroke risk, as well as how diuretics fit into the equation.
Should you make sure to eat your bananas? Certainly…as well as citrus fruits, green leafy vegetables, avocados, milk, and nuts, which are all good sources of potassium. Regardless of stroke risk, eating a healthful diet that includes potassium-rich foods is a good way to maintain overall good health.
Green DM, et al. Serum potassium level and dietary potassium intake as risk factors for stroke. Neurology . August 2002;59:315-320.
Levine SR and Coull BM. Potassium depletion as a risk factor for stroke. Neurology . August 2002;59:302-303.
Last reviewed Aug 14, 2002 by ]]>Elizabeth S. Smoots, MD]]>
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