Blood pressure is measured using two numbers that represent the force exerted by blood against the artery walls as the heart works through its cycle. The top number, systolic pressure, measures the force when the heart contracts and pumps blood out. The bottom number, diastolic pressure, reflects the force when the heart muscle rests and refills between beats. When the diastolic number is consistently elevated, it suggests a problem with the vascular system during the resting phase. Understanding the causes of high diastolic pressure and its implications is the first step toward effective management.
Understanding Diastolic Blood Pressure
Diastolic pressure represents the sustained pressure within the arteries during the period when the heart is relaxed. This measurement primarily reflects the resistance encountered by blood flow in the smaller arteries and arterioles, known as peripheral vascular resistance. When these small vessels constrict or lose elasticity, the resistance increases, which in turn elevates the diastolic number. A healthy diastolic reading is considered to be below 80 millimeters of mercury (mmHg).
Current guidelines classify a diastolic reading between 80 and 89 mmHg as Stage 1 hypertension, and 90 mmHg or higher as Stage 2 hypertension. The condition known as Isolated Diastolic Hypertension (IDH) occurs when the diastolic pressure is 80 mmHg or higher, but the systolic pressure remains below 130 mmHg. IDH is often seen more frequently in younger adults, typically those under the age of 55, before age-related arterial stiffening causes the systolic number to rise more dramatically.
An elevated diastolic number signifies constant, unremitting strain on the entire cardiovascular system, even when the heart is resting. This continuous force can impair the delivery of oxygen to the heart muscle itself and is linked to an increased risk of heart disease and stroke, especially in middle-aged individuals. While high systolic pressure is a stronger predictor of risk in older adults, a high diastolic reading should always be addressed to protect the health of the arteries over time.
Primary Contributors to Elevated Diastolic Pressure
The most direct cause of a high diastolic number is an increase in systemic vascular resistance, which is the tension in the small blood vessels. Several underlying factors contribute to this increased resistance by disrupting the normal relaxation and widening of the arteries. Long-term, unmanaged stress is a significant contributor because it triggers the release of hormones like adrenaline and cortisol. These hormones cause the small arteries to constrict, a process called vasoconstriction, which immediately increases peripheral resistance and elevates diastolic pressure.
Dietary choices also play a large role through the regulation of fluid volume and vascular tone. A high intake of sodium causes the body to retain water, which increases the total blood volume that must be pushed through the circulatory system. This excess volume places greater pressure on the vessel walls, leading to a higher diastolic reading. Similarly, conditions that affect the body’s fluid and hormonal balance, such as chronic kidney dysfunction, can raise blood pressure by impairing the kidneys’ ability to manage salt and water effectively.
Underlying health issues can also directly affect the mechanisms that control vascular tone. Endocrine disorders, like thyroid problems, or conditions causing hormonal imbalances can stimulate the sympathetic nervous system, leading to chronic vasoconstriction.
Medications That Affect Diastolic Pressure
Some commonly used medications can inadvertently contribute to elevated diastolic pressure. Over-the-counter decongestants, which contain ingredients like pseudoephedrine or phenylephrine, work by narrowing blood vessels to relieve nasal swelling, but this action also raises blood pressure throughout the body. Nonsteroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen and naproxen, can also raise pressure by causing the body to retain fluid and sodium while affecting kidney function. When high diastolic pressure is observed, review all medications and supplements with a healthcare provider to identify any potential drug-induced causes.
Immediate and Long-Term Management Strategies
Managing high diastolic pressure begins with actionable adjustments to daily habits that directly target peripheral resistance and fluid volume. Dietary modification is foundational, emphasizing reducing sodium intake to less than 1,500 milligrams per day to prevent excess fluid retention. Following the principles of the DASH (Dietary Approaches to Stop Hypertension) eating plan—which prioritizes foods rich in potassium, magnesium, and calcium—can help counteract the effects of sodium and promote better blood vessel relaxation.
Structured physical activity is also a powerful tool for improving vascular health. Aim for at least 150 minutes of moderate-intensity aerobic exercise each week, such as brisk walking or cycling. Exercise improves the elasticity of blood vessels, reducing the resistance they place on blood flow and helping to lower the diastolic number. Techniques for managing chronic stress, such as meditation, deep breathing, and ensuring adequate sleep, directly address the hormonal triggers that cause vasoconstriction.
For long-term management, consult a healthcare provider to determine if medication is needed, especially if lifestyle changes are insufficient to bring the diastolic pressure below 80 mmHg. Treatment aims to reduce peripheral resistance and decrease blood volume. Common medication classes include:
- Angiotensin-converting enzyme (ACE) inhibitors and Angiotensin II Receptor Blockers (ARBs): These relax blood vessels by blocking the hormonal system that causes constriction.
- Calcium channel blockers (CCBs): These prevent calcium from entering the muscle cells of the heart and blood vessels, allowing the vessels to widen.
- Diuretics: Particularly thiazide diuretics, these help the body eliminate excess salt and water, which decreases blood volume and lowers pressure.
It is important to know the signs of a hypertensive crisis, which requires immediate medical attention. These include a diastolic reading of 120 mmHg or higher accompanied by symptoms like chest pain, severe headache, sudden vision changes, or difficulty breathing.