Kidney disease affects a large number of people in the United States and the condition often goes undetected.

New research examines the impact of kidney disease on cardiovascular health and highlights the importance of screening for kidney disease.

Kidney disease is one of the leading causes of death in the U.S., with approximately 31 million people living with chronic kidney disease.

Because kidney disease often does not present any symptoms at its onset, the ailment frequently goes unnoticed. That is why it is sometimes referred to as a “silent disease.”

It is estimated that as many as 9 out of 10 people with moderately reduced kidney function do not know that they have kidney disease. 

The impact of the disease is sizable, however.

The National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) estimates that chronic kidney disease occurs in 14 percent of the U.S. population.

In addition, more than 660,000 people in the country have kidney failure. In 2013, more than 47,000 people died of kidney disease in the United States.

It is known that people with chronic kidney disease are also at an increased risk of cardiovascular disease.

According to the NIDDK, almost 70 percent of people aged 66 and above who have chronic kidney disease also have cardiovascular disease.

In this context, an international team of researchers led by Dr. Bernadette Thomas from the University of Washington in Seattle investigated the prevalence of kidney disease in relation to cardiovascular-related deaths at six points in time between 1990 and 2013.

The findings were published in the Journal of the American Society of Nephrology.

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Cardiovascular vs. kidney failure deaths

Specifically, Thomas and team looked at kidney disease stages 3, 4, and 5, examining their prevalence in 188 countries that were included in the Global Burden of Disease Study.

According to the NIDDK, there are five stages of chronic kidney disease, each corresponding to different degrees of kidney function.

They range from normal kidney function (at stage 1) to kidney failure, at which point either dialysis or a kidney transplant is often needed for survival.

The stages considered in the study correspond to a mild to severe loss of kidney function, severe loss of kidney function, and kidney failure.

Thomas and team estimate that worldwide, 2.2 million deaths in 2013 were linked to reduced kidney function. This amounts to 4 percent of the total number of deaths in that year.

More than half of these deaths (around 1.2 million) were cardiovascular and 960,000 deaths were caused by kidney failure.

The researchers also looked at how reduced kidney function ranked in comparison with metabolic risk factors for cardiovascular disease during the time period studied.

They found that kidney disease fell behind high body mass index (BMI), high systolic blood pressure, and high fasting blood glucose, which is a marker of prediabetes.

As a risk factor for premature death, disability, and poor health, reduced kidney function was on par with high total cholesterol levels.

This was calculated using disability-adjusted life years (DALY) as a metric, and the results were valid for both developed and developing countries throughout the world. One DALY refers to one year of life lost to poor health.

Thomas highlights the importance of the study for understanding the real effect that kidney disease has on cardiovascular health in various countries around the world. She also stresses the necessity of kidney disease screening.

“Understanding the true health impact of kidney disease on society necessitates considering cardiovascular as well as end-stage renal disease deaths and disability,” she said. “This is especially important within the developing world, where the death rate has increased since 1990.”

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