Tune into your pulse. The beating of your heart is the work of an amazing organ. In an average lifetime, the heart beats more than 3 billion times, pumping the equivalent of more than 900 million gallons of blood. Two important age-related struc­tural changes in the heart are the accumulation of fat deposits and the stiffening of the heart muscle caused by tissue changes. By the late 40s and early

86 CHAPTER 3

50s, the fat deposits in the lining around the heart may form a continuous sheet. Meanwhile, healthy muscle tissue is being replaced by connective tis­sue, which causes a thickening and stiffening of the heart muscle and valves. These changes reduce the amount of muscle tissue available to contract the heart. The net effect is that the remaining muscle must work harder. To top it off, the amount of blood that the heart can pump declines from roughly 5 liters per minute at age 20 to about

3.4 liters per minute at age 70 (National Institute on Aging, 2008).

The most important change in the circulatory system involves the stiffening (hardening) of the walls of the arteries. These changes are caused by calcification of the arterial walls and by replacement of elastic fibers with less elastic ones.

The combination of changes in the heart and the circulatory system results in a significant decrease in a person’s ability to cope with physical exertion, especially aerobic exercise. By age 65, the average adult has experienced a 60 to 70% decline in the aerobic capacity since young adulthood. However, if you stay in good shape throughout adulthood, the decline is much less (National Institute on Aging, 2008). This decline is one reason why older adults who are not in good shape are more likely to have heart attacks while performing moderately exert­ing tasks such as shoveling snow. The changes that occur with aging in the heart related to exercise are shown in Figure 3.5.

Cardiovascular Diseases. In the United States, some­one dies from cardiovascular disease every 33 seconds (American Heart Association, 2004). It is the leading cause of death in all ethnic groups in the United States and in many other countries. The prevalence of cardiovascular disease increases dra­matically with age, with the rates for men higher until age 75, when the rates for women are higher. Rates of cardiovascular disease have been declin­ing in the United States among men since the 1980s (American Heart Association, 2007). These declines may be deceiving, though, because key risk factors are actually increasing; for example, over 66% of adults are classified as overweight, and rates of diabetes are going up.

At the start of At the end of

heart beat, at rest. heart beat, at rest.

Size at the start of Size at the end of

heart beat is the heart beat is smaller

same as at rest. than at rest.

During Vigorous Exercise

At the start of At the end of

heart beat, at rest. heart beat, at rest.

Figure 3.5 The Heart: Young and Old.

Source: National Institute on Aging (2008). Aging hearts and arteries: A scientific quest. Retreived September 3, 2008, from http://www. nia. nih. gov/HealthInformation/Publications/AgingHeartsandArteries/default. htm. Design by Levine and Associates, Washington, DC.

There are important ethnic and gender dif­ferences in cardiovascular disease. Why? Ethnic differences may be caused by differential genetic predisposition, quality of and access to health care, diet, weight, and stress (American Heart Association, 2008a). Although many people believe that gender differences can be traced to hormonal protection in premenopausal women caused by estrogen, the elimination of the gender gap by age 75 is not caused mostly by the lack of estrogen in postmenopausal women. Rather, the difference has more to do with the leveling off of death rates in men (Avis, 1999). However, menopause is associated with lower levels of HDL (“good”) cholesterol and higher levels of LDL (“bad”) cholesterol (Brown et al., 1993), so the full role of estrogen in cardiovascular disease has yet to be uncovered.

Several types of cardiovascular disease are note­worthy. Congestive heart failure occurs when car­diac output and the ability of the heart to contract
severely decline, making the heart enlarge, pressure in the veins increase, and the body swell. Congestive heart failure is the most common cause of hospi­talization for people over age 65. Angina pectoris occurs when the oxygen supply to the heart muscle becomes insufficient, resulting in chest pain. Angina may feel like chest pressure, a burning pain, or a squeezing that radiates from the chest to the back, neck, and arms (Mayo Clinic, 2007b). In most cases the pain is induced by physical exertion and is relieved within 5 to 10 minutes by rest. The most common treatment of angina is nitroglycer­ine, although in some cases coronary arteries may need to be cleared through surgical procedures or replaced through coronary bypass surgery.

Heart attack, called myocardial infarction (MI), occurs when blood supply to the heart is severely reduced or cut off. Mortality after a heart attack is much higher for older adults (Centers for Disease Control and Prevention, 2008a). The initial

Physical Changes 87

symptoms of an MI are identical to those of angina but typically are more severe and prolonged; there may also be nausea, vomiting, severe weakness, and sweating, which Steve experienced in the vignette. Thus, Grace is right to be concerned about Steve’s symptoms. In as many as 25% of patients, how­ever, chest pain may be absent. These “silent” heart attacks are more common in older adults, especially those with diabetes (Centers for Disease Control and Prevention, 2008b). Treating heart attack victims of all ages includes careful evaluation and a prescribed rehabilitation program consisting of lifestyle changes in diet and exercise.

Atherosclerosis is an age-related disease caused by the buildup of fat deposits on and the calcification of the arterial walls (Mayo Clinic, 2008b). Much like sandbars in a river or mineral deposits in pipes, the fat deposits interfere with blood flow through the arteries. These deposits begin very early in life and continue throughout the life span. Some amount of fat deposit inevitably occurs and is considered a normal part of aging. However, excess deposits may develop from poor nutrition, smoking, and other aspects of an unhealthy lifestyle.

When severe atherosclerosis occurs in blood vessels that supply the brain, neurons may not receive proper nourishment, causing them to malfunction or die, a condition called cerebrovas­cular disease. When the blood flow to a portion of the brain is completely cut off, a cerebrovascular accident (CVA), or stroke, results. Estimates are that every 53 seconds someone in the United States has a CVA, making stroke one of the most common forms of cardiovascular disease (Centers for Disease Control and Prevention, 2008b). Causes of CVAs include clots that block blood flow in an artery or the actual breaking of a blood vessel, which creates a cerebral hemor­rhage. The severity of a CVA and likelihood of recovery depend on the specific area of the brain involved, the extent of disruption in blood flow, and the duration of the disruption. Consequently, a CVA may affect such a small area that it goes almost unnoticed, or it may be so severe as to cause death. Two common problems following a CVA are aphasia (problems with speech) and hemiplegia (paralysis on one side of the body).