What is pulse pressure and why are people talking about it?
Pulse pressure refers to the difference between the systolic (top) and diastolic (bottom) blood pressure. If your blood pressure (BP) is 120/80, for instance, your pulse pressure is 120 - 80 = 40 mmHg. A pulse pressure of 40 mmHg is normal.
Why does this matter? Does it add important information beyond knowing just your systolic and diastolic values?
Before we answer this question, let's consider what the two basic values mean in the first place.
Think of a piston that cyclically forces water into a pipe: It pushes forward, then rests; pushes forward, then rests. The pressure within the pipe when the piston pushes forward is systolic pressure; the pressure in the pipe when the piston is resting is the diastolic pressure.
As in the make-believe pipe, systolic blood pressure in the body is the pressure felt in the arteries (pipe) while the heart is contracting (like a pumping piston) and pushing blood rapidly forward. The heart squeezes most of its contents out, then relaxes. The pressure remaining after relaxation of the heart is the diastolic pressure.
As we age, systolic blood pressure (at least in Western societies) increases. Starting in our 20s and 30s, systolic pressure climbs higher and higher as we get older. Systolic pressure increases primarily due to increasing stiffness of the large arteries of the body, especially the aorta (the large artery that first receives the blood ejected by the heart) and its large tributaries. Increased blood volume within this enclosed space can also increase systolic pressure.
Diastolic pressure behaves differently. Up until age 50 or so, diastolic pressure increases in parallel with systolic pressure. After age 50, however, diastolic and systolic pressures part ways, and diastolic pressure trends downward while systolic pressure continues its climb upward. This occurs because the small, "downstream" vessels in muscles and organs become stiff, slowing "runoff" of blood into all the small blood vessel tributaries. There are also complex effects, such as "reflected waves" of pressure that can contribute to dropping diastolic pressure and increasing pulse pressure of aging. Because pulse pressure is the difference between the two values, pulse pressure increases as systolic and diastolic pressures diverge. Thus, BP of 120/80 at age 25 yields a pulse pressure of 40 mmHg, while a BP of 160/65 at age 75 yields a pulse pressure of 95 mmHg.
There are also unusual causes for a widened pulse pressure, such as a leaky aortic valve (aortic valve "insufficiency"), arteriovenous malformations (hidden connections between arteries and veins), and thyroid disease, issues best considered by your doctor.
Both systolic and diastolic hypertension have been associated with increased risk for stroke and heart attack, with risk beginning as low as a systolic pressure of 115 mmHg, diastolic pressure of 75 mmHg. Cardiovascular risk increases as either or both pressures increase, though systolic pressure is probably a better predictor than diastolic.
Some authorities have proposed that pulse pressure and systolic pressure represent a gauge of "arterial age," with higher values for either or both signifying greater age, lesser values more youthful age.
Pulse pressure is also associated with risk for cardiovascular risk independent of systolic and diastolic pressure. While there is some disagreement about what constitutes a true risk level, it is generally agreed that a pulse pressure of 65 mmHg or greater carries additional risk, whether or not systolic and diastolic hypertension are present. In men, a pulse pressure of 70 mmHg or greater triples heart attack risk compared to a pulse pressure of 50 mmHg or less. In most studies, the relationship of pulse pressure and cardiovascular risk in females is much weaker.
People with diabetes may develop cardiovascular risk at a somewhat lower pulse pressure. The Hoorn Study, for example, showed that diabetic men with a pulse pressure of 60 mmHg were more likely to suffer a fatal heart attack. This may even apply to younger people (40 to 60 years old) with diabetes; a Japanese study showed that a pulse pressure of 53 mmHg or greater carried a 20% incidence of heart attack over 8 years, while a pulse pressure lower than 53 mmHg carried only 4% incidence.
Efforts to decrease systolic pressure with changes in lifestyle or medications are more effective at reducing risk for cardiovascular events. This, of course, reduces pulse pressure. However, there are no studies that suggest that increasing a low diastolic pressure to narrow the pulse pressure is of any benefit and, in fact, may be detrimental.
If you have a high pulse pressure or systolic pressure, what should you do about it? There are a number of useful strategies to consider that can reduce pulse pressure and systolic pressure and minimize the need for medication, including:
1) Exercise - Exercise is fabulously effective for reducing blood pressure.
Reductions of 10 mmHg in both systolic and pulse pressure are common.
2) Weight loss-Loss of even a few pounds can yield a profound effect.
3) Carbohydrate reduction - Carbohydrates, especially those made with wheat flour, cornstarch, and sugars, make us fat and hypertensive. Reduction or elimination of these foods yields large reductions in systolic and pulse pressure.
4) Vitamin D - Vitamin D is a natural blocker of the angiotensin converting enzyme that increases systolic and pulse pressure. While the effect is modest, generally a BP reduction of no more than 5-8 mmHg, everyone should be aware of their vitamin D status anyway, given its considerable health implications.
5) Magnesium - We should be able to obtain magnesium from our drinking water if we drank from nearby rivers and streams. That, of course, is no longer safe in the modern world and municipalities filter the water for you. But they remove all magnesium in the process. Magnesium deficiency increases systolic and pulse pressure; restoration reduce them. Well-absorbed forms of magnesium include magnesium glycinate and magnesium malate. Systolic and pulse pressure reductions of 5-10 mmHg are most common, though may require many years to develop.
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