Introduction

Your heart and blood vessels undergo changes with aging and these changes are risk factors for age-associated diseases. Previous articles (one through eight) in this series have explained how aging "itself" affects your heart. In upcoming articles we are going to discuss why "aging" is risky and whether there is anything that you can do to minimize harmful age-associated changes and also protect yourself from diseases that commonly occur with aging.

High Blood Pressure At Any Age Is Risky!

Over 50% of persons in industrialized nations in their 6th decade have what doctors call "hypertension", or "high blood pressure". The medical profession once believed that an increase in systolic blood pressure as one aged was perfectly normal. But, now we know that high blood pressure at any age is dangerous!

Less than 50 years ago, doctors and epidemiologists (the scientists who compile data on disease occurrence and outcomes), debated as to whether or not high blood pressure numbers (both diastolic and systolic) were dangerous to one's health. Then the Cooperative Veterans Administration Study on Hypertension lead by Edward Fries of the Veterans Administration Hospital in Washington, D.C., proved that high blood pressure was indeed dangerous, and leads to an increase in cardiovascular diseases, like stroke. Numerous subsequent systematic studies corroborated Dr. Fries' findings. It should be noted, however, that these early studies about blood pressure concentrated mostly on the bottom number or diastolic pressure, because at the time during which these studies were conducted it was thought that increases in the top number, or systolic pressure, were not so important if the lower number, or diastolic pressure, was not increased. So, it was thought that increased systolic blood pressure occurred along with an increase in the diastolic blood pressure and that the systolic blood pressure was an "innocent bystander" and not of significance. Now we know differently.

What is Blood Pressure?

"Blood pressure" refers to the pressure within the aorta and the large arteries that branch from it. Blood pressure as measured in the clinical practice of medicine has two components, systolic (top or higher number) and diastolic (lower number). The higher number is the maximum pressure which occurs when the heart contracts (systole), and the lower number is the lowest pressure measured when the heart begins to relax between beats (diastole), just before the next contraction.

What Determines Systolic and Diastolic Pressure

The stiffness of your large arteries and the volume of blood pumped into them during your heartbeat determine systolic pressure. Diastolic pressure is largely regulated by the tone (numbers of and degree of constriction) of your body's smaller arteries called arterioles. Arteriolar "tone", or tightness of these vessels, is determined in part by brain blood vessel communication via sympathetic and parasympathetic nerves. (See Article #7 "Brain-Heart Communication Withers With Aging"). Arteriolar tone is also regulated by metabolic factors, (for example, temperature, oxygen and carbon dioxide levels in the blood), and by a large number of chemical substances produced within the body, among which is nitrous oxide. Nitrous oxide is a substance produced by the cells that live on the inside layer of your blood vessels (endothelial cells).

High Systolic Blood Pressure Was Previously Considered Normal in Older Persons

How is it that a high level of systolic blood pressure in the elderly was once considered to be "normal"? The reason was twofold: a lack of research data, and a misinterpretation of the information available to physicians.
Research data on elevated systolic pressure in older persons was not available to researchers and physicians. This was because, older persons were previously excluded from most blood pressure studies and other clinical investigations designed to evaluate risk factors for cardiovascular diseases such as stroke and heart attacks. This seems paradoxical, given that it is usually older persons who suffer from these diseases. Yet, until relatively recently, this bias against the elderly in clinical trials was the rule rather than the exception.

The information that was available regarding blood pressure in the elderly was then misinterpreted and a mistaken theory took hold. The major cause of an increase in systolic pressure that accompanies aging is stiffening of the large arteries as we age. At the time when doctors initially realized that diastolic blood pressure elevations could be dangerous, it was also widely recognized that hardening, or stiffening, of the arteries occurred with aging, and that this caused the top pressure number (systolic) to increase and the bottom (diastolic) to decrease. Thus, with aging, the difference between the top and bottom number (pulse pressure) also increased. In the absence of evidence to the contrary, it was argued that increased systolic pressure and increased pulse pressure, in the absence of an increase in diastolic pressure, reflected "normal aging" of the large arteries, due to an increase in their stiffness. In fact, it was believed by many doctors that older persons required an increased systolic pressure to force the blood through their hardened arteries.

New Evidence Proved Elevated Systolic Pressure to be as Dangerous as Elevated Diastolic Pressure

Fortunately, the nonsense about increased systolic pressure being needed to force blood through older hard arteries and not being dangerous was laid to rest about a decade ago by evidence provided by the National Institutes of Health's (NIH) Framingham Study. This epidemiological study proved beyond a doubt that elevated systolic pressure, or a pressure greater than 160 mmHg, was in fact as dangerous as elevated diastolic pressure, particularly in older persons. A subsequent NIH supported clinical trial (The Systolic Hypertension Trial In Elderly Persons ((SHEP)) went on to demonstrate that treatment of isolated increased systolic pressure (defined as a systolic pressure of greater than 160 mm Hg with a normal diastolic pressure) in persons 60 and over, reduced the risk of stroke and heart disease, and of premature death attributable to these. Actively treating high blood pressure in the trial resulted in a 36% decrease in both fatal and nonfatal strokes. The findings regarding the risk of elevated systolic blood pressure by the NIH clinical trial were corroborated by subsequent studies in Europe and other countries.

Lowering the Bar for Blood for a Healthy Blood Pressure at Any Age

During the last few years additional evidence compiled by epidemiologic studies has resulted in "lowering the bar" for a healthy blood pressure at any age to levels not to exceed 140/90 mm Hg at rest. This most recent recommendation is that of the Joint Sixth National Committee on Hypertension, the USA body that sets the national guidelines for treatment of high blood pressure.

What Causes Changes In Blood Pressure?

Your blood pressure is determined by the interaction of dozens of factors among which are: the status of your arteries, stress, NaCl (salt) intake, heart function, body weight and body composition, physical conditioning status, and hormonal and complex genetic factors, which remain to be determined. The importance of each factor varies among individuals, and within an individual under different circumstances.
With arteriosclerosis that accompanies aging the large arteries lose their normal flexibility and become thickened and stiff, so that these arteries can't expand as they once did when the heart pumps blood through them. As the blood is forced into the older stiffer arteries, the systolic pressure increases more than it would in a softer artery. This is shown in the following illustration.

Young and Old Arteries During Diastole and Systole (cross sections)

Arterial walls in younger persons expand as the heart pumps blood through them.

Thickened and stiff arterial walls lose flexibility and can't expand when the heart contracts.

As blood is forced into them blood pressure increases more than in younger persons.
Arteriosclerosis affects mostly large arteries like the aorta and those arteries that supply blood to your brain. An increase in arterial stiffness can also affect other mechanisms that control blood pressure. For example, arteriosclerosis in the kidney's arteries can impair their ability to rid the body of salt and water, which would increase the blood pressure.

Blood Pressure in the Arteries is Increased:
1. When the heart pumps with more force with each beat (as happens during exercise).
2. When the blood volume increases (as when kidneys fail and salt and water are not removed from the body).
3. When there is constriction of blood vessels (resulting from stimulation by nerves or hormones).
4. When the larger arteries lose their normal flexibility and become stiff so they do not expand as normal arteries do when the heart pumps blood through them. This "hardening of the arteries" or arteriosclerosis accompanies aging.

Why Is High Blood Pressure "Risky"?

High blood pressure is "risky" because it causes a deterioration of your blood vessels. This eventually causes the blood vessels to burst or become blocked. Both scenarios lead to a lack of blood supply to body organs, which produces heart attacks or strokes. Thus, its not the blood pressure number itself, that's the major problem, but rather the high risk of blood vessel damage that accrues over time when arterial pressure exceeds an optimal level on a long term basis.

The Evidence Is At Hand, But Is Not Being Heeded!

While the evidence regarding optimal blood pressures is now at hand, particularly systolic and pulse pressure (systolic minus diastolic) in older persons, the evidence often is not being heeded as it ought to be by physicians and patients. This is evidenced by the high percentage of persons with blood pressure above the optimal level. Why is this? Are these persons either not being advised about lowering their blood pressure by their physician; or are they not seeking medical advice to lower their pressure by either lifestyle or pharmacological means, or a combination of both? Do such afflicted persons even realize that they have a blood pressure that is above the optimal level with regard to successful aging?
There may be several explanations for the apparent lack of attention with respect to the treatment of elevated blood pressure. On the patient side, individuals may be unaware of what their pressure is, perhaps because high blood pressure usually causes no pain or other symptoms. On the physician side, many doctors are not yet accustomed to the new guidelines for treating blood pressures in the range of 140/160 systolic or 90/100 diastolic (mm Hg), particularly in older persons.

What Can You Do Today To Decrease Your Risk?

To decrease your risk of damage to your blood vessels due to untreated high blood pressure, first get your blood pressure checked. You can use the chart below to determine if you have high blood pressure and if you do what category you fall into.
If your pressure exceeds the optimal level, decide with your physician what measures you ought to take to lower it. These may be life style changes, medication or both. Remember that untreated high blood pressure:

1. Increases the risk for heart disease such as heart attack and heart failure.
2. Increases the risk for kidney failure.
3. Increases the risk for stroke.

Our next article in this series will focus on the specific processes which occur in the vessels with aging that make the vessels harden and cause the older person to have an abnormal blood pressure and to be prone to strokes.

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