Elevated levels of blood pressure, or hypertension, have been observed since the development of blood pressure measurements in the 1800s. It was soon recognized that populations with a high frequency of elevated blood pressure were also populations with a high frequency of strokes, yet the dangers of high blood pressure often went unappreciated until recent years.
High blood pressure is a condition that historically has affected both the privileged and the underprivileged in our society. Presidents Woodrow Wilson and Franklin Delano Roosevelt both had high blood pressure and suffered strokes and heart disease. Today, the condition is disproportionately present among African Americans—15 to 20% have some degree of elevated blood pressure.
For many years, high blood pressure was considered a consequence of disease rather than its cause. Clinicians seeing a patient with a stroke, for instance, often attributed their elevation in blood pressure to the stroke rather than the other way around. Long-term studies, such as the Framingham Heart Study, which followed a large number of individuals for many years, established that the high blood pressure actually preceded strokes and not the other way around. High blood pressure as a contributory cause of strokes, as well as heart and kidney disease, was fully confirmed only after randomized controlled trials in the late 1960s and early 1970s established that lower blood pressure leads to reduced frequency of these diseases. Screening for high blood pressure became widespread in the same period in large part as a result of these investigations.
Elevated levels were initially defined as 140/100 or greater, based upon a range of normal obtained by measuring the blood pressure on large numbers of adult Americans. What were once considered acceptable levels of blood pressure have been redefined as elevated levels in recent years. Today, the desirable level is considered 120/80 or lower. These changing levels are justified by follow-up data from a large number of individuals that demonstrates that even levels of blood pressure only slightly above 120/80 are associated with increased risk of stroke and heart disease.
The fluctuating levels of blood pressure often make it difficult to establish an individual’s average level. Electronic monitoring of blood pressure over a 24-hour period has become a feasible and acceptable gold standard for establishing an individual’s average level. Early detection and successful treatments have been shown to effectively reduce the consequences of high blood pressure. Weight loss and salt restriction are often prescribed initially, with subsequent introduction of one or more drugs. Most, if not all, individuals with elevated blood pressure respond to drug treatment with tolerable or no side effects, but need to continue treatment for many years—usually for the rest of their lives.
A national public health campaign began in the 1970s to encourage individuals to know their blood pressure and to urge clinicians to treat detected elevated levels. In recent decades, national surveys have indicated that a gradually increasing percentage of patients with elevated blood pressures are being successfully treated and that there has been a substantial reduction in strokes and deaths from strokes. Recent evidence showing that reducing the high salt levels in the U.S. diet can reduce the average level of blood pressure has prompted renewed public health efforts to change eating habits and the contents of commercial foods.
Today, treatment of high blood pressure is recognized as one of the most cost-effective interventions. Its cost per quality adjusted life-year (QALY) saved is only a few thousand dollars a year for the average person. For high-risk groups, such as those with diabetes, it actually saves money to monitor and treat high blood pressure rather than allow it to cause or exacerbate other health problems requiring more expensive treatments.