Systolic blood pressure is the higher of the two numbers in a blood pressure reading — the peak pressure in the arteries when the heart muscle contracts and pumps blood out. It is written above the diastolic pressure, as in 120/80, where 120 is the systolic value. Systolic pressure rises with exertion, stress, and age, as arteries stiffen, and a persistently high reading — generally 130 or above — is a major risk factor for heart attack, stroke, and kidney disease. Diet influences it: excess salt, alcohol, and obesity push it up, while potassium-rich foods, weight control, and regular activity bring it down. It is measured with a cuff and is one of the most important vital signs in preventive medicine.