Your blood pressure is the measure of the force of your blood against the artery walls, and it is described using two numbers: systolic and diastolic. Systolic pressure is the pressure exerted as your heart beats; diastolic pressure is the pressure exerted as your heart relaxes between beats. A normal blood pressure reading used to be less than 140/90 mmHg, with 120/80 mmHg as the ideal. But recent changes in the guidelines set normal as less than 120/80 mmHg.
It is normal for your blood pressure to fluctuate during the day due to physical activity or stressful stimuli; it should return to normal as your body adjusts to whatever situation you're in. If it does not, if your blood pressure is chronically elevated to greater than 140/90 mmHg, then the condition is called hypertension. Hypertension is unfortunately common, affecting more than 50 million Americans.
We used to think that only diastolic pressure was an important predictor of cardiovascular events, but it is now understood that both numbers matter. Elevated systolic pressure is a key indicator of stroke risk, especially in the elderly. Left uncontrolled, it can also result in kidney disease, vascular disease, and increased risk of heart attack.
The most common cause of hypertension is aging. Blood vessels lose their elasticity as we age, and that reduction in the ability to expand and contract can lead to a rise in systolic pressure and a decrease in diastolic pressure. A young, healthy artery reacts just like a balloon would in response to increased pressure-it expands. Older arteries aren't always flexible enough to do so, which means blood ends up pressing against the artery wall with greater force.
Another common cause of hypertension is heredity predisposition. Someone with a strong family history of hypertension is at higher risk of developing hypertension later in life than someone with no family history.
Hypertension that is caused by certain treatable conditions is called secondary hypertension. Nutritional causes are surprisingly common. One question I always ask patients is if they eat licorice.