Blood pressure is a measurement of the force exerted by circulating blood against the walls of the arteries. This reading is a primary indicator of cardiovascular health and is always presented as two numbers separated by a slash. These two values represent the pressure during the two different phases of the heart’s pumping cycle. Monitoring these numbers offers insights into how efficiently the heart is working and the overall condition of the blood vessels. Maintaining a healthy range is a preventative measure against serious conditions like stroke and heart attack.
Defining Systolic and Diastolic Pressure
The top number in a blood pressure reading is the systolic pressure (SBP), which measures the maximum force exerted on the artery walls. This peak pressure occurs during systole, the phase when the heart muscle contracts. During systole, the left ventricle forcefully pushes blood into the aorta and major arteries. The systolic reading reflects the pressure generated by the heart’s pumping action and the resistance within the arteries as they receive this rush of blood.
The bottom number, the diastolic pressure (DBP), measures the lowest pressure within the arteries. This minimum force is recorded during diastole, the phase when the heart relaxes and refills with blood between beats. The diastolic number is an important indicator of the elasticity of the artery walls. It shows how well the blood vessels maintain pressure when the heart is not actively contracting.
Understanding Blood Pressure Categories
Health guidelines classify blood pressure readings into specific categories to guide monitoring and treatment. A Normal reading is defined as a systolic pressure of less than 120 mm Hg and a diastolic pressure of less than 80 mm Hg. Maintaining this range is associated with the lowest risk for cardiovascular events.
The next category is Elevated blood pressure, which is a systolic reading between 120 and 129 mm Hg and a diastolic reading of less than 80 mm Hg. This range indicates that action, typically focused on lifestyle changes, should be taken to prevent progression to hypertension.
Stage 1 Hypertension is diagnosed when the systolic pressure is between 130 and 139 mm Hg or the diastolic pressure is between 80 and 89 mm Hg. This level suggests a need for focused lifestyle modifications and, sometimes, the introduction of medication, especially if the patient has other risk factors. Stage 2 Hypertension is defined as a systolic pressure of 140 mm Hg or higher or a diastolic pressure of 90 mm Hg or higher. Readings in this stage almost always require a combination of lifestyle changes and medication to prevent serious health complications.
The most severe category is a Hypertensive Crisis, defined as a blood pressure reading of 180/120 mm Hg or higher. This is a medical emergency that requires immediate attention, especially if accompanied by symptoms like chest pain or severe headache. Conversely, low blood pressure, or Hypotension, is generally defined as a reading lower than 90/60 mm Hg. While often harmless, a sudden drop can cause dizziness or fainting because not enough blood reaches the brain.
Factors Influencing Your Readings
A single blood pressure reading can be influenced by many temporary factors, so readings are typically averaged over multiple measurements. Emotional states, such as stress or anxiety, cause the body to release hormones like adrenaline. This temporarily increases heart rate and constricts blood vessels, resulting in a spike in both systolic and diastolic pressure. This phenomenon is sometimes referred to as “white coat syndrome” when it occurs due to nervousness in a clinical setting.
Dietary choices play a substantial role in maintaining stable pressure over time. High sodium intake encourages the body to retain fluid, which increases blood volume and consequently raises blood pressure. Conversely, consuming foods rich in potassium can help balance the effects of sodium by promoting its excretion. Regular physical activity helps keep vessels flexible and lowers resting heart rate, while a lack of exercise contributes to higher readings.
Non-modifiable factors also affect blood pressure, including age and genetics. As individuals age, the walls of the arteries naturally become stiffer, which contributes to a general rise in systolic pressure. Genetic predisposition can influence how an individual’s body regulates blood pressure. This means some people may be more susceptible to hypertension regardless of lifestyle.