The cardiovascular system is sometimes called the circulatory system because it is comprised of the heart, blood, and blood vessels (arteries, veins, and capillaries). Because it is responsible for circulating oxygen and nutrients to all parts of the body, it is, understandably, one of the body systems most affected by age.The walls of the arteries thicken, lose their elasticity, and become stiffer. This causes a decrease in blood flow to vital organs and causes blood pressure to rise. Major age-related changes include the following:
Blood
- A decreased hematocrit (the number of erythrocytes in the whole blood) can lead to anemia, as well as certain dietary deficiencies. Erythrocytes also help in the transport of oxygen and carbon dioxide and in maintaining a normal acid/base balance.
- Peripheral veins become constricted or blocked by the formation of stationary blood clots (thrombus). These can dislodge, causing an embolism in the lungs or an extremity, thus shutting down circulation. When this happens, it most often means an amputation.
- Because the valves in leg veins are often not able to work to capacity, blood often pools causing swelling of the lower extremities.
- One thing that does remain constant with age is the volume and composition of blood. This means that most lab values remain normal. Abnormal lab values for blood tests usually indicate alterations in other organ systems. For instance, fasting blood glucose level increases with aging but not as a result of changes in the blood. Rather, it is the result of age-related changes associated with insulin. The same holds true for serum lipids. While serum lipids increase 25-50% after the age of 55, the increase results from an altered metabolism and not to changes in the blood or blood-forming organs.
- The amount of red bone marrow decreases with age, causing a decline in the formation of new blood cells. Therefore, recovery from bleeding episodes will be slowed.
- Age-related decline also occurs in WBC (white blood cell) activity. Although WBC activity increases in response to infection, it does so more slowly. Cardiac muscle fibers and neurons cannot be replaced, and cumulative lapses result from even relatively minor damage.
Blood Vessels
- Blood vessel walls become thicker and tougher. Since the walls no longer have the elasticity to adjust to sudden changes in blood pressure, there is an increased risk of aneurysms.
- As the inner surface of blood vessels become roughened, age-related changes cause an increased risk in the development of fatty plaques and of thrombus formation.
- Weakened vascular walls also collect calcium salts, which increase the risk of heart attack or stroke.
- As the walls of veins weaken and stretch, their valves become incompetent. This is more likely to occur in the legs where the walls are subject to greater pressure as the blood struggles to return to the heart against the force of gravity. As a result, distended superficial veins develop (varicose veins). An inflammation, called phlebitis, also occurs more often in the elderly.
- Baroreceptors become less sensitive; therefore, adjustments to changes in position are slowed, causing an increase in dizziness and falling.
Heart
- There is a reduction in exercise cardiac output. Because the heart is not able to pump the blood as efficiently, circulation is slowed. In addition, the heart cannot respond as quickly, or as forcefully, to the increased workload of the exercised heart. Exertion, sudden movements, and changes in position may cause a decrease in cardiac output, resulting in dizziness and loss of balance. However, opinions vary as to whether or not there are changes in the resting cardiac output. In general, heart resting output is decreased to 80% by age 50 and to 70% of capacity by age 70. When output does decline, it is often associated with such other age-related processes as atherosclerosis. A reduction in cardiac output leads to pooling of blood in the legs, cold extremities, and edema.
- The health of the myocardium (the heart’s muscular wall) depends on blood supply, and with age, the likelihood of atherosclerosis increases, causing the coronary arteries to narrow, restricting the vital blood supply.
- High blood pressure (hypertension) causes the left ventricle to work harder. It may enlarge and outgrow its blood supply and thus becomes weaker.
- Several structural changes in the heart contribute to the impaired response to exercise:
- heart muscle loses elasticity and becomes more rigid;
- heart valves become thickened by fibrosis and more rigid (leading to murmurs);
- the number of pacemaker cells decreases;
- aging heart cells have a decreased ability to use oxygen;
- arrhythmias are more common with age as the cells of the conduction pathway become less efficient.
- An age-related increase occurs in blood pressure. As a result, the heart needs to work harder to pump blood into the systemic circulation.
