Hypertension, more commonly known as high blood pressure, is defined as a systolic reading of 140 mm Hg or higher (the top number of a blood pressure reading) or a diastolic reading of 90 mm Hg or higher (the bottom number).

Systolic pressure measures the pressure exerted on the artery walls when the heart beats; diastolic pressure measures the force on the arteries between heartbeats.

In 2002, the American Medical Association (AMA) warned that the majority of the estimated 50 million Americans with hypertension, also known as high blood pressure, were failing to keep it "under control." A year later, few people seem to have heeded that warning, a point emphasized by this study published in the association's main journal.

Researchers surveyed a random sampling of the U.S. population as part of the latest National Health and Nutrition Examination Survey (NHANES), gathering data on prevalence, awareness, treatment and control of high blood pressure. Results were compared with data from the two phases of NHANES III (1988-91 and 1991-94).

As of 1999-2000, 28.7 percent of NHANES participants suffered from high blood pressure - a 3.7 percent increase from 1988-91. Moreover, the condition was controlled in only 31 percent of patients - albeit a 6.4 percent increase from 1988-91. Increasing age, female gender and high body mass index (BMI) were associated with a higher risk of hypertension.

So, now you know all about high blood pressure. The question is, "What are you going to do about it?" If you're one of the millions who suffer, talk to your doctor about the best way to keep it under control.

Hajjar I, Kotchen TA. Trends in prevalence, awareness, treatment and control of hypertension in the United States, 1988-2000. Journal of the American Medical Association, July 9, 2003:290(2), pp199-206.