By Nipun Arora, MD, and Kevin C. Dellsperger, MD, PhD

Hypertension, or high blood pressure (HBP), is the leading preventable cause of death in the world. Hypertension is defined as either a systolic BP >140 mmHg or diastolic BP >90 mmHg, currently being treated with antihypertensive medications, or having been told at least twice by a physician or health professional that one has HBP. About 73 million people, approximately one-third of the population in the United States age 20 and older, have HBP. Of these individuals, two-thirds have uncontrolled hypertension and one-third are not even aware of their condition. In fact, many people have HBP for years without knowing it. Despite efforts in public awareness and the large number of new drug therapies for HBP over the last decade, the death rate from hypertension in the United States increased 26.6 percent, and the actual number of deaths rose 56.1 percent. This is why HBP is often called the “silent killer.” With escalating obesity and aging population in the United States, the prevalence of HBP is projected to rise further.

Cause or Effect
HBP is the silent killer since it is associated with many diseases that result in high levels of mortality and morbidity. Long standing HBP is associated with higher incidence of heart attack, stroke, congestive heart failure and chronic kidney disease (CKD). More than 70 percent of people who have a first heart attack, a first stroke and have congestive heart failure have HBP. Diabetes and the metabolic syndrome (sometimes referred to as pre-diabetes) are also associated with HBP. It is critical to maintain optimal blood pressure control to prevent complications of HBP. The risks of HBP begin to increase as the blood pressure rises above 110/85 mmHg.

Role of High Blood Pressure in Kidney Disease
Whereas hypertension is present in one-third of adults in the general population, it is present in 75 percent of adults with diabetes and over 90 percent of those with CKD. HBP may result in the development of kidney disease and failure, but some kidney diseases can result in the development of HBP. Diabetes and CKD dramatically increases the cardiovascular risk associated with hypertension, and the presence of hypertension greatly accelerates the progression to end-stage renal disease (ESRD). The recommended treatment goal for hypertension in the general population is less than 140/90 mm Hg, while in high-risk patients with diabetes or CKD (with proteinuria), blood pressure of less than 130/80 is considered to be optimal.

Why should I control my blood pressure?
HBP plays an important role in coronary and peripheral atherosclerosis. It is estimated that control of HBP to below 140/90 mmHg could, in men and women, prevent 19 and 31 percent of coronary heart disease events, respectively. HBP constitutes a major risk factor for dissection of the aorta, abdominal aortic aneurysm (AAA), and peripheral arterial disease. One-time abdominal ultrasound screening for AAA is recommended after age 65 in smokers and in those with severe systolic hypertension. In addition, HBP is also a major risk factor not only for stroke but also for dementia, often the two most dreaded complications of aging. It accounts for over 50 percent of strokes. In hypertensives, 80 percent of the strokes are ischemic (a restriction in blood supply) and 20 percent hemorrhagic (excessive bleeding). There is a marked increase in the onset of ischemic stroke in the morning hours, corresponding to the morning surge in BP.

Hypertension is the second most common cause of CKD (diabetes is first). In patients with HBP, the presence of kidney damage dramatically increases the risk of a cardiovascular event. Most patients with hypertension-induced kidney damage die of heart attack or stroke before renal function deteriorates sufficiently to require chronic hemodialysis.

The prevalence of HBP increases with age, rising exponentially after age 30. Before age 50, the prevalence of HBP is somewhat lower in women than in men. After menopause, the prevalence of HBP increases rapidly in women and exceeds that in men. Eventually, by age 75, almost 90 percent of the individuals in the United States have HBP. The African-American population is the worst affected by HBP, and the prevalence of hypertension in blacks is among the highest in the world. Compared with whites, blacks develop HBP earlier in life, and their average blood pressure is much higher. As a result, compared with whites, blacks have a 1.3-times greater rate of nonfatal stroke, a 1.8-times greater rate of fatal stroke, a 1.5-times greater rate of heart disease death and a 4.2-times greater rate of ESRD.

Despite strong clinical evidence, hypertension is often under-diagnosed and under-treated. There are a number of potential reasons, including poor access to healthcare and medications, and lack of adherence with long-term therapy for a condition that is usually asymptomatic. Compliance to therapy is also reduced when it interferes with the patient’s quality of life and the immediate benefits may not be obvious. Several studies have shown control of HBP may require combination therapy. But, even physicians appear reluctant to make such changes to drug therapy, which would lead to more effective treatment of HBP.

Optimal control of hypertension is crucial, and can reduce the risk of stroke by 35-40 percent, heart attack by 20-25 percent and heart failure by more than 50 percent. Regular follow-up with a physician is required for close management of HBP, and to address associated risk factors including smoking, obesity, increased cholesterol and sleep apnea.

Nipun Arora, MD, is Chief Fellow in Cardiovascular Medicine at the University of Missouri, Columbia. He has published several articles regarding cardiovascular complications in dialysis patients.

Kevin C. Dellsperger, MD, PhD, FAHA, FACC, FACP, is the Marie L. Vorbeck Chairman and Professor in Internal Medicine and Medical Pharmacology and Physiology. He is a Fellow of the American Heart Association Council for High Blood Pressure Research and Past President of the Heartland Affiliate of the AHA.

This article was originally published in the December 2008 issue of Kidney Beginnings: The Magazine.

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