Chronic kidney disease is often closely linked to other chronic conditions. While it can sometimes be difficult to discern whether the presence of one condition is correlated to another, hypertension has long been one of the most relevant determinants of whether an individual may experience kidney failure.
More than half of people with chronic kidney disease have hypertension, more commonly known as high blood pressure. In fact, high blood pressure is the second leading cause of kidney failure in the United States, after diabetes. This linkage is important because not only does high blood pressure increase the likelihood that kidney disease could worsen, it also increases the chances that a person will develop heart disease, the leading cause of death in the United States.
But why is it that these two conditions are so closely linked?
High blood pressure is an increase in the force that blood puts on blood vessels as it moves through the body. High blood pressure can restrict and narrow blood vessels, damaging and weakening them throughout the body, including in the kidneys, which are tasked with removing waste and extra water to make urine. Any damage to the blood vessels in the kidneys – or reduced blood flow – makes it more difficult for them to filter out waste and extra fluid. In turn this extra fluid can increase the body’s blood pressure even more, causing additional damage to the kidneys. This dangerous cycle can lead to kidney failure or other serious conditions.
But while high blood pressure can cause kidney disease, it can also result as a symptom of kidney disease. Damage of any kind to the kidneys puts additional pressure on its blood vessels, making it more difficult for the body to control blood pressure, leading to hypertension.
There are a number of factors that increase odds for hypertension, especially in patients with existing kidney disease or damage. These include age, a family history of hypertension, poor eating habits or excessive alcohol consumption. Men and African American patients are also more likely to suffer from hypertension.
Studies have also shown increased risks for pregnant women correlating hypertension and kidney disease. According to a study published in the Journal of the American College of Cardiology, “Twice as many women who experienced a hypertensive disorder during any of their pregnancies were at increased risk of developing heart or kidney diseases earlier in life based on incidence per woman versus per pregnancy.” Hypertensive disorders of pregnancy (HDP) include preeclampsia, gestational hypertension, chronic hypertension and superimposed preeclampsia (women with chronic hypertension who develop preeclampsia). Women who have preeclampsia during pregnancy are at risk for death from heart disease as early as the first decade after giving birth.
This was one of the first studies to analyze incidence of hypertensive disorders per woman instead of per pregnancy.
"Despite the rates of HDP increasing over the past three decades, the incidence rates of HDP per-pregnancy and per-woman had not yet been studied," said Vesna D. Garovic, MD, PhD, professor of medicine in the department of Internal Medicine and Obstetrics and Gynecology at Mayo Clinic and lead author of the study. "By only looking at HDP rates per-pregnancy, we have been vastly underestimating the number of women who are affected by this condition and may be at risk for future heart or kidney disease. Looking at the per-woman rate allowed us to assess women with more than one pregnancy, who may have had HDP, including preeclampsia, during one of her pregnancies, but not the other."
While there is still much research to be completed around hypertension, kidney disease and pregnancy, the correlation between kidney disease and hypertension in the general population in undeniable.
The most important thing to note is that there are things you can do to protect your health. As with many chronic diseases, you can decrease your odds of getting hypertension by increasing physical activity, maintaining a healthy weight, not smoking, managing stress and eating a healthy diet with decreased sodium. The American Heart Association provides a number of recommendations for changes you can make to manage high blood pressure on their website.