Blood pressure has two components: the higher systolic when your heart contracts, and the lower diastolic when your heart relaxes. You have high blood pressure when your systolic is above 120 or your diastolic is above 80. Ninety-one percent of Americans will eventually develop high blood pressure, which increases their risk for heart attacks, strokes, diabetes, kidney damage and other blood vessel disease.

Doctors do not diagnose high blood pressure with a single reading because some people have reactive hypertension that is not as dangerous as persistent hypertension. If you get one high reading in your doctor's office, check your own blood pressure daily and chart the results. You can use the self-test stations that are available in many pharmacies, or buy your own blood pressure cuff for about fifty dollars.

Healthy people have their blood pressures drop in the evening. The person at highest risk for heart attacks and strokes is the one whose high blood pressure does not drop in the evening. If your blood pressure is above 120/80 consistently, particularly in the evening, you have high blood pressure and are at significant risk for serious disease. Check back with your doctor who will usually evaluate you for other risk factors for a heart attack and may prescribe drugs. Whether or not you take medication, you can improve blood pressure with lifestyle changes: diet and exercise. More than 80 percent of hypertensive Americans can bring their blood pressures to normal within a few weeks just by following a diet that emphasizes fruits, vegetables, whole grains, beans and other seeds (the DASH diet, NIH Publication No. 03-4082.)

A recent study confirms that exercising regularly lowers blood pressure to prevent heart attacks and strokes (Medicine & Science in Sports & Exercise, August 2005). The researchers showed that you can lower high blood pressure on the first day of vigorous exercise. However, if you are out of shape, a single bout of intense exercise can cause a heart attack. Check with your doctor, then get a personal trainer or join a health club and learn how to begin a safe and effective exercise program.

Gabe Mirkin, M.D.

Dr. Gabe Mirkin has been a radio talk show host for 25 years and practicing physician for more than 40 years; he is board certified in Sports Medicine and three other specialties.

Dr. Mirkin's daily features on fitness have been heard on CBS Radio News stations since the 1970's. He has written 16 books including The Sportsmedicine Book, the best-selling book on the subject that has been translated into many languages. His latest book is The Healthy Heart Miracle, published by HarperCollins.

Dr. Mirkin is a graduate of Harvard University and Baylor University College of Medicine. A Boston native, Dr. Mirkin did his residency at the Massachusetts General Hospital. He has served as a Teaching Fellow at Johns Hopkins Medical School, Assistant Professor at the University of Maryland, and Associate Clinical Professor in Pediatrics at the Georgetown University School of Medicine. He has run more than forty marathons and is now a serious tandem bicycle rider with his wife, nutritionist Diana Mirkin.