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Low potassium level associated with high blood pressure, despite salt intake, CV risk factors

Tuesday, November 18 2008 | Comments
Evidence Grade 7 What's This?
A low potassium level in the urine correlates to elevated blood pressure, particularly in black patients, according to a recent study.

Investigators analyzed data on 3,303 participants of the Dallas Heart Study, which is a multi-ethnic population-based cohort oversampled for black patients. Blood pressure was measure during the same visit in which fasting blood and first void urine samples were taken. A multivariable linear regression model was used to evaluate whether there was an association between systolic blood pressure and urine potassium, urine sodium, and urine sodium to potassium ratio. The models were adjusted for age, sex, race, body mass index, estimated GFR, hypercholesterolemia, diabetes, and smoking history.

Overall, the prevalence of hypertension was 36%. Hypertensive patients tended to be older, had a higher BMI, had lower GFR, and were more likely to be black. Subjects with hypertension were also more likely to have hypercholesterolemia, diabetes, and a history of smoking.

Results showed that the amount of potassium in urine samples was strongly related to blood pressure.

"The lower the potassium in the urine, hence the lower the potassium in the diet, the higher the blood pressure. This effect was even stronger than the effect of sodium on blood pressure," said lead investigator Dr. Susan Hedayati, of the University of Texas Southwestern Medical Center, in a written statement.

The association between low potassium and high blood pressure persisted even after taking into account age, race, and other cardiovascular risk factors. However, the researchers warned that the study is limited by the fact that people in the Dallas Heart Study were not following a specific diet.

On a related note, Dr. Chou-Long Huang, a co-author of the study, has found evidence that a gene called WNK1 may be responsible for potassium's effect on blood pressure. Dr. Huang and colleagues are currently conducting a trial in which participants are on a fixed potassium diet and the activity of the WNK1 gene is being monitored.

"Future studies will test the hypothesis that increased WNK1 expression may mediate hypertension in dietary potassium deficiency," the authors wrote. (Abstract SA-FC404)

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