High blood pressure (hypertension) is a very common condition in Western civilization. It is strongly associated with stroke, dementia and heart attack. It is quite treatable. Yet many studies suggest that a third of the over fifty million Americans with hypertension aren't aware of their diagnosis, and another third are not being treated effectively. So what's the problem?
Hypertension isn't a disease-it's a description. It's a measurement. It requires an intact animal to measure and to study. It can't be studied in a test tube or measured in blood. What constitutes high blood pressure hasn't remained the same. The threshold for "high" is much lower than it was twenty years ago. Different professional organizations (American Heart Association, American Diabetes Association, American Society for Hypertension) define hypertension differently and suggest different goals for treatment. Patients and often their physicians are confused about where their pressure should be and how to get there.
Most people are aware that their blood pressure is reported as two numbers. The higher number is the "systolic" pressure and the lower number the "diastolic" pressure. The difference between systolic and diastolic pressure is called the "pulse pressure." Most early research focused on diastolic pressure and early trials used diastolic pressure to determine the blood pressure lowering effects of anti-hypertensive drugs. These trials were performed largely in middle-aged men. We now know that particularly as patients age their systolic blood pressure is a much more important indicator of their risk for vascular disease. Pulse pressure is also a strong predictor of risk for heart attack and stroke. As we age (at least in Western cultures) there is a gradual rise in systolic blood pressure. Physicians were formerly trained that this is a "normal" phenomenon and that we should not treat hypertension in the elderly with the same vigor as in younger patients. We now know that there is no age at which blood pressure lowering does not provide benefit - a recent trial of patients in their eighties showed that blood pressure lowering reduced their risk for stroke and heart attack.
Even how we measure blood pressure has become controversial. A recent trial suggested that measuring blood pressure in the upper arm often does not reflect the pressure in the aorta and blood vessels supplying the heart, brain and kidneys ("central blood pressure"). Disease in these vessels causes heart attack, stroke and chronic kidney disease. Importantly some very widely used blood pressure lowering drugs used in that trial did not lower central blood pressure as well as arm ("brachial") pressure. These drugs were not as effective in reducing risk for heart attack and stroke as drugs with more pronounced effects on aortic pressure. Does the blood pressure measured in the doctor's office reflect our pressure at home or at the office? Should we measure our pressure in the morning (when it is usually the highest) or later in the day? Before or after exercise or after taking our medicines? Is it important that our blood pressure "dip" at night while we sleep (probably yes)?
