As individuals age their body’s ability to adapt to environmental stresses, trauma, illness and medications weaken. One of the factors that is believed to contribute to these problems is a decline in immune system responses. Elderly persons are more susceptible to infections than younger persons and show evidence of immune complex disorders. (Porth, 2005) The immune system is affected by aging in many ways. One reason the elderly have a lowered resistance to disease and infection can be traced to the thymus gland. Between sexual maturity and middle age the thymus gland, which regulates the development of T-lymphocytes, normally shrinks by about 90 percent. Another factor contributing to immune system decline is a decline in pituitary function while endorphin levels rise with age, which may explain why elderly patients have decreased awareness of painful events like MI. Also, body temperature regulation which is under the control of several glands is impaired due to a drop in metabolic rate. It is important to note that trouble in one system can have a domino effect. For example, a hip fracture can quickly develop problems with circulation, skin breakdown, pulmonary function, voiding and constipation. (p. 49)
Along with immune function changes, it is often difficult to diagnose infection in the elderly client because signs and symptoms of disease and injury are often vague or atypical. According to Andresen, the myocardium changes with age losing elasticity as some muscle fibers are replaced by fibrotic collagen and others become hypertrophied. These changes, along with thicker and stiffer valves may reduce cardiac output. (p. 45) The elderly become predisposed to cardiac conduction disorders and dysrhythmias also become common. The cause for most cardiac disorders is the buildup of connective tissue in the SA and AV nodes and the decline in the pacemaker cells. Valves in the peripheral venous circulation also work less effectively causing vessels to become engorged. Elderly patients often display isolated systolic hypertension which is related to loss of arterial elasticity or compliance with aging. The increase in aortic stiffness leads to a rise in systolic blood pressure and reduction of aortic volume which in turn causes a decline in diastolic run-off and reduction in diastolic blood pressure. (Baruch 2004)
Often, elderly patients are prone to fatigue, dizziness and falls in part because the heart cannot respond as quickly to sudden movements, exertion or changes in position. It is, therefore, common for the elderly, who rise quickly from the supine position to become dizzy. This condition, called “orthostatic hypotension” is one in which the baroreceptors in the aortic arch and carotid sinus become less sensitive, impacting the blood vessels in such a way that they are less able to constrict in response to rapid changes in position. (p. 46) Along with orthostatic hypotension the elderly persons display a loss of bone mass regardless of sex, race or body size. With aging, the process of bone formation is slowed in relation to bone breakdown, resulting in a loss of bone mass and weakened bone structure. (Porth, 2005) A progressive decline in height especially among older women is commonly attributed to compression of the spinal column as the vertebral discs and vertebrae thin. Bone loses minerals as it ages, increasing the risk of fractures. Immobilization or excessive calcium loss via the bowel or kidney can accelerate the process. Cartilage around the joints deteriorates and there is a gradual reduction in bone mass. (p. 48) As bone cells weaken osteoporosis most often develops in the aging individual. Type II or senile osteoporosis, caused by a calcium deficiency, is a slow process in which cortical and trabecular bone are lost. Often the first manifestations of the disorder are those that accompany a skeletal fracture- a vertebral compression fracture; or fractures of the hip, femur; and pelvis. (Porth, 2005)
Gastrointestinal changes in the elderly persons also become visible. For example, calcification of costal cartilage and partial contraction of the inspiratory muscles limit the older person’s ability to fully expand the chest. Coughing and gag reflexes and ciliary action in the bronchial lining are also less efficient, making it even more difficult to clear secretions. Peristalsis in the esophagus is no longer triggered with each swallow. The lower esophageal sphincter often fails to relax, delaying the entry of food into the stomach, causing a premature feeling of fullness. Weakening of sphincter tone and the diaphragm muscles around the hiatus can cause heartburn or reflux. These factors, along with a weakened gag reflex heighten the risk of aspiration.
Another physiological function which begins to decline early is the pulmonary function in which the lungs lose elasticity, reducing vital capacity- the maximum amount of air that can be exhaled from the point of maximum inspiration. (Porth, 2005) When the lungs lose elasticity the alveolar ducts and bronchioles enlarge and the number of alveoli decreases causing the lungs not to inflate well during inhalation and patients have a hard time expelling secretions; residual volume- amount of air left in the lungs after maximum expiration- also increases. Slowing of respiratory rate and shortness of breath during episodes of increased oxygen demand may also be observed. The thoracic cage will also have an observable change mostly noted as an increase in the anteroposterior diameter of the chest. (p. 46)
The elderly patient is now also more susceptible to glucose intolerance because fasting serum glucose increases with age. Delayed insulin release by the pancreas, reduced tissue sensitivity to insulin or both, causes decreasing glucose tolerance. (p. 49) The kidney’s ability to filter blood is also affected by increasing age because tissue growth and renal blood flow decrease and there is a loss of nephron units. By age 90 the glomerular filtration rate (GFR) declines by as much as 50 percent. (p. 46) The decline in GFR that occurs with aging is not accompanied by an equivalent increase in serum creatinine levels because the production of creatinine is reduced as muscle mass declines with age. Health care providers need to be extra vigilant when prescribing and calculating drug doses for medications that are eliminated through the kidneys. If not carefully addressed, improper drug dosing can lead to an excess accumulation of circulating drugs and result in toxicity. (Porth, 2005) Sensory changes also take place in the elderly individual.
1. Presbyopia- is the permanent loss of accommodation of the crystalline lens of the eye that occurs when people are in their mid-40s, marked by the inability to maintain focus on objects held near to the eye.
2. Presbycusis- progressive loss of hearing with aging, typically resulting from sensorineural hearing loss. (Taber’s Cyclopedic Medical Dictionary, 2005)
The elderly also display decreased sensitivity to outside stimuli which also slows response time. All senses become less acute such as vision, hearing and receptivity to pain.
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