Chapter 16
Infection
On completion of this chapter, the reader will be able to:
1. Describe alterations in the immune system related to aging.
2. Describe nutritional factors that influence immune status.
3. Describe psychosocial factors that influence immune status.
4. Describe the effect of lifestyle factors on immune status.
5. Describe the effect of medications and drugs on immune status.
6. Identify strategies to prevent nosocomial and/or community-acquired infections.
7. Incorporate nutritional, psychosocial, and lifestyle factors into a nursing care plan.
The importance of investigating infections in the elderly cannot be overstated. Infection is one of the 10 most common causes of death in clients older than age 65 (Kane, Ouslander, Abrass, & Resnick, 2009). Infections in the elderly are often masked in their presentation, which can lead to delayed treatment. The immune system, which enables the body to defend itself against outside infections and altered cells such as neoplasms within the body, is vital to human survival. Yet with aging this system exhibits a diminished ability to provide such protection (Newson, 2007). Considering this system’s fundamental importance to maintaining health, a clear understanding of the age-related changes in the immune system is crucial.
The immune system has two primary functions: (1) to discriminate between that which is self and that which is nonself and (2) to remove from the body that which is recognized as nonself. The system accomplishing this comprises several organs, cells, and proteins (Porth, 2004). Furthermore this system interacts with the neurologic and endocrine systems in a highly complex manner to modulate function of the human immune response. Thus immunologic functioning can be mediated by psychologic and behavioral factors. There is an increasing awareness of the impact of mood, activity level, stress, and nutrition on the capacity of this system to provide optimum protection.
The Chain of Infection
A number of pathogens can invade the body through inhalation into the respiratory tract and can cause disease. These diseases include influenza, the common cold, and bacterial pneumonia. The portal of entry does not limit the site of infection. Ingested pathogens may penetrate the mucosa, disseminate through the circulatory system, and cause disease in other organs (Porth, 2004). Hepatitis A and vancomycin-resistant enterococci (VRE) are examples of ingested pathogens causing infection in the liver and bloodstream, respectively. The host and the condition of the host are important factors in determining whether a pathogen will succeed in causing infection and clinical disease.
Age-Related Changes in the Immune System
Some researchers believe that much of the illness seen in older adults may be the direct consequence of changes in “both cell-mediated and antibody-mediated immune response” (Townsend, 2008). Alterations in immune status can be responsible for infections, cancer, and autoimmune processes, all of which can be life threatening (Porth, 2004). Scientists have tried to determine whether the diminished immunocompetence noted with age is a result of decreased numbers of immune cells or merely decreased functioning of the cells. However, because immunocompetence is affected by numerous other factors, it has been difficult to isolate changes that are related to age alone. Thymic atrophy, which occurs naturally with aging, affects T-lymphocyte function. Diminished cellular (T cell–mediated) and humoral (B-lymphocyte) immunity have both been associated with aging. Box 16–1 summarizes age-related changes in the immune system (Townsend, 2008).
Cell-mediated immunity is the ability of the host to differentiate between self and nonself. Diminished cell-mediated immunity in older adults is generally associated with declining T-cell function. In addition, T-cell response also diminishes. Functional responses can occur in older adults, but these responses tend to be weaker than earlier in life (Goldman & Ausiello, 2004). The effect of aging on B cells is less clear.
The skin is the largest immunologically active system of the body, and the body’s first line of defense. With aging, the skin becomes more fragile and prone to breakdown or abrasion. Current immunity theories attempt to explain a relationship between decreased immune functioning and elevated autoimmune response. Is there a connection between functioning of the immune system and age-related conditions such as Alzheimer disease or cardiovascular disease (Miller, 2004)?
Factors Affecting Immunocompetence
Nutritional Factors
Nutritional and dietary status is of critical importance to immune function. This is especially true in the older adult population. Older adults are at high risk for nutritional deficits in that at least one third of individuals older than age 65 having nutritional deficiencies (review Chapter 10). Risks associated with the development of a nosocomial infection include poor nutrition, unintentional weight loss, low serum albumin levels, decreased fluid intake, poor oral hygiene, and altered mental status. Numerous factors that may contribute to this tendency toward inadequate nutrition include altered taste, social isolation, physical inability to prepare food, altered absorption, and poverty. Individuals with nutritional deficiencies have been shown to have significant reductions in delayed cutaneous hypersensitivity (Eliopoulos, 2005). Nutritional supplements have been found to allow older individuals to handle activities of daily living and to decrease a patient’s susceptibility to infection (Nowson, 2007).
Protein-Energy (Caloric) Malnutrition
Significant deprivation of protein and energy (caloric) nutrients has been shown to result in alteration in immune function (Nowson, 2007). These, along with other changes, result in increased susceptibility to infectious disease. Restoring nutritional balance, especially protein balance, can improve older adults’ immune status (Nowson, 2007).
Iron and Trace Element Deficiency
Zinc is thought to be associated with immune function. A prolonged zinc deficiency leads to impaired cell-mediated immunity, wound healing, and protein synthesis. Patients with decreased zinc levels experience an increase in the number of infections and an increase in the needed healing time (Nowson, 2007).
Psychosocial Factors
Depression
Depression has also been associated with decreased immune capacity. This is significant because approximately 15% of community-dwelling older adults have symptoms of depression (review Chapter 14). Furthermore, adults older than 65 years represent 13% of the population but make up 18% of all suicides (Vance, Moneyham, & Farr, 2008). There is some evidence that the negative impact of depression on the immune system increases with age. Thus older adults who are depressed may be at risk for greater immune deficiencies than younger depressed individuals.
Common Problems and Conditions
The immune deficits seen so often in older adults make this population more vulnerable to both infection and cancer, thus contributing to increased rates of infections such as pneumonia and influenza, as well as a wide variety of malignancies. As people age, the likelihood increases that autoimmune antibodies will be found in serum, which suggests an increased likelihood of autoimmune processes. However, there is controversy over whether such autoimmune processes are actually age related (Kane et al, 2009).
Numerous infections are possible for individuals with diminished immune capacity. Some of the more common infections in older adults include influenza, pneumonia, tuberculosis, urinary tract infections (especially in women), and shingles (herpes zoster). (See Chapter 24 for additional information.) With diminished IgA production, the barriers of skin and mucous membranes are less effective. Furthermore, as these barriers become more fragile with aging, the entry of pathogens is more easily achieved. Medical management of infections consists primarily of determining the source of the infection and prescribing the appropriate antibiotic or antiviral medication. See Box 16–2 for examples of autoimmune diseases.
Influenza and Pneumonia
Pneumonia and influenza are ranked as the fifth leading cause of death in the elderly (Kane et al, 2009). More deaths from influenza occur in the 65 or older age group than in any other age group (Eliopoulos, 2005). The predominant portal of entry is inhalation of small droplets transmitted through sneezing, coughing, or talking. Closed populations such as those in long-term care facilities provide an ideal setting for the spread of influenza. The social environment in these institutions also facilitates transmission of influenza through group activities, communal dining rooms, and rehabilitation activities.
The most effective measure to control influenza is the vaccination of persons at high risk. Influenza vaccination is a Medicare-covered benefit for older adults, yet only approximately 60% of the population 65 years or older is vaccinated. If an individual has had a reaction to a previous vaccination or is allergic to eggs, caution should be used (Wallace, 2008). Other strategies to control the nosocomial spread of influenza include the early identification and grouping of infected clients, careful hand washing, and the use of barrier precautions when handling bodily substances, especially respiratory secretions.
Pneumonia may follow influenza or develop independently. Fifty percent to 75% of community-acquired pneumonias are caused by pneumococcal infections. More than 80% of nosocomial pneumonias are caused by gram-negative microorganisms (Wachtel & Fretwell, 2007).
The major host factor associated with community-acquired pneumonia is advanced age (Wachtel & Fretwell, 2007). Smoking, alcohol abuse, chronic lung disease, recent history of viral upper respiratory tract infection, and neurologic disease (which may contribute to microaspiration of secretions from the oropharynx) are other contributing factors. Pneumonia follows aspiration of the organism into the lungs. The aging lung has impaired functioning, which allows the organisms to survive and multiply. Social environments such as congregate housing, communal dining rooms, churches, crowded shopping centers, day care centers, or nursing facilities place older adults at risk for exposure and infection. However, social isolation is not recommended because of its negative psychologic consequences. Older adults should be encouraged to select activities that may reduce the infection risk during the colder months.
Vaccination against pneumococcal infection is the primary prevention strategy, even though its effectiveness is still arguable (Eliopoulos, 2005). Infection control measures should be implemented immediately. Hand washing, monitoring fluids and nutritional intake, and proper disposal of bodily secretions help to manage infection (Eliopoulos, 2005). Older adults and their families should be instructed to seek early medical attention for subtle changes that may signal the onset of infection. For example, pneumonia may be seen in patients with confusion or tachypnea and no other findings. Signs and symptoms may not exist or, at least, be diminished on presentation. Nursing care is similar to that of younger patients. Because of the importance of early detection of subtle changes, nursing care of older patients must be attentive (Eliopoulos, 2005). (See Chapter 24 for more information.) Precautions recommended to individuals throughout their lives take on added importance with aging. For example, older adults need to maintain tetanus immunization every 10 years because their immune response may be diminished.
Cancer
Neoplasms occur with greater frequency in older adults. Common types of cancer in older adults include lung cancer, breast cancer, and prostate cancer. However, the potential for numerous other forms of cancer should not be overlooked. A wide variety of types of cancer are possible in older adults. (See Chapter 19 for more information.)
