We’ll bet if you asked most people what they want out of life, they would say something about a good quality of life. But what does that mean? Precise def­initions are hard to find. Sometimes people find it easier to say what quality of life is not: being depen­dent on a respirator while in a permanent vegetative state is one common example. Researchers, though, like to be more specific. They tend to look at several specific aspects of quality of life: health-related quality of life and non-health-related quality of life. Health-related quality of life includes all of the aspects of life that are affected by changes in one’s health status. Non-health-related quality of life refers to things in the environment, such as entertainment, economic resources, arts, and so on that can affect our overall experience and enjoy­ment in life.

Most research on quality of life has focused on two areas: quality of life in the context of specific diseases or conditions and quality of life relating to end-of-life issues. We briefly lay out the issues here and return to them as we discuss specific situations in this chapter and in Chapters 5 (interventions that increase quality of life) and 13 (end-of-life issues).

In many respects, quality of life is a subjective judgment that can be understood in the context of broader models of adult development and aging. One such model describes ways in which people select domains of relative strength, optimize their

116 CHAPTER 4 use of these strengths, and compensate for age- related changes (Baltes et al., 2006). In addition, one must also consider not only the physical health aspects but also mental health in assessing quality of life (Kaplan et al., 2004). From this perspective, quality of life is a successful use of the selection, optimization, and compensation model (SOC) to manage one’s life, resulting in successful aging. Applying this approach to research in health care, quality of life refers to people’s perceptions of their position in life in context of their culture (Karim et al., 2008).

In general, research on health-related quality of life addresses a critical question (Lawton et al.,

1999) : To what extent does distress from illness or side effects associated with treatment reduce the person’s wish to live? Lawton and colleagues (1999) show that the answer to this question depends a great deal on a person’s valuation of life, the degree to which a person is attached to his or her present life. How much one enjoys life, has hope about the future, and finds meaning in everyday events, for example, has a great deal of impact on how long that person would like to live.

Narrowing the focus of the quality-of-life con­cept as it relates to specific conditions brings us to the domains of physical impairment or disability and of dementia. Quality of life in the former con­text includes issues of environmental design that improve people’s functioning and well-being, such as handicapped accessible bathrooms and facili­ties (Lawton, 1999). We examine environmental influences in Chapter 5. Quality of life is more dif­ficult to assess in people with dementia, although new assessment instruments have been developed (Karim et al., 2008). For example, the quality of life of residents in Alzheimer’s treatment centers is complex (Hubbard et al., 2003). We consider this issue in more detail in Chapter 10 when we focus on Alzheimer’s disease.

Changes in the Immune System

Every day, our bodies are threatened by invaders: bacterial, viral, and parasitic infections (as well as their toxic by-products) and abnormal cells such as precancerous and tumor cells. Fortunately

© iStockphoto. com/nano

How much a person enjoys everyday tasks, such as working the daily crossword puzzle, affects how that person may want to live.

for us, we have a highly advanced defense system against foreign invaders: the immune system. The National Cancer Institute provides a Web-based overview of how our immune system works; check it out at http://www. cancer. gov/cancertopics/ understandingcancer/immunesystem.

Much about how our immune system works remains unknown. For instance, one great mystery is how the immune system learns to differentiate your own cells from invaders. Researchers think the mechanism involves recognizing certain sub­stances, called antigens, on the surface of invading bacteria and cells that have been taken over by viruses. Regardless of how this actually happens, once the immune system has learned to recog­nize the invader, it creates a defense against that invader.

How does this defense system work? It’s an amaz­ing process that is based essentially on only three major types of cells that form a network of interact­ing parts (Sompayrac, 2008): cell-mediated immu­nity (consisting of cells originating in the thymus gland, or T-lymphocytes), humoral immunity based on antibodies (B-lymphocytes), and nonspecific immunity (monocytes and polymorphonuclear neu­trophil leukocytes). The primary job of the T – and B-lymphocytes is to defend against malignant (can­cerous) cells, viral infection, fungal infection, and

some bacteria. Natural killer (NK) cells are another, special type of lymphocytes that monitor our bod­ies to prevent tumor growth and are our primary defense against cancer, although how this happens is not fully understood (Sompayrac, 2008). NK cells also help fight viral infections and parasites. In addition, there are five major types of specialized antibodies called immunoglobulins (IgA, IgD, IgE, IgG, and IgM). For example, IgM includes the “first responders” in the immune system, IgE is involved in allergies and asthma, and IgG (also called g-glob – ulin) helps fight hepatitis.

How does aging affect the immune system? Researchers are only beginning to understand this process, and there are large gaps in the literature (Sompayrac, 2008). Moreover, the immune system is sensitive to a wide variety of lifestyle and envi­ronmental factors, such as diet, stress, exercise, and disease, making it very difficult to isolate changes caused by aging alone (Aldwin & Gilmer, 2004; Burns & Leventhal, 2000).

Changes in health with age provide insights into immune functioning. Older adults are more suscep­tible to certain infections and have a much higher risk of cancer (both of which are discussed in more detail later in this chapter), so most research­ers believe that the immune system changes with age. Indeed, NK cells and several other aspects of the immune system decrease in effectiveness with age (Srinivasan et al., 2005). For one thing, older adults’ immune systems take longer to build up defenses against specific diseases, even after an immunization injection. This is probably caused by the changing balance in T-lymphocytes and may partially explain why older adults need to be immunized earlier against specific diseases such as influenza. Similarly, B-lymphocytes decrease in functioning. Research examining the administra­tion of substances such as growth hormones to older adults to stimulate lymphocyte functioning indicates that some specific lymphocyte functioning returns to normal with treatment, and can regener­ate the thymus gland, both of which are important in treating individuals with HIV (Chidgey, 2008). This process for T- and B-lymphocytes is described in Figure 4.3.

Longevity, Health, and Functioning 117

Young thymus Thymosin production T-cell lymphocytes

Thymus involutes between ages 12 and 35

Old thymus

Decreased thymosin production Decreased T-cell function

Figure 4.3 Process of aging of the immune system.

Source: Reprinted with permission from Ebersole, P, & Hess, P, Toward Healthy Aging (5e, p. 41) Copyright © 1998 Mosby St. Louis: with permission from Elsevier.

The changes in immune system function have important implications (Aldwin & Gilmer, 2004; Srinivasan et al., 2005). Older adults become more prone to serious consequences from illnesses that are easily defeated by younger adults. In addition, various forms of leukemia, which are cancers of the immune cells, increase with age, along with other forms of cancer. Finally, the immune system can begin attacking the body itself in a process called autoimmunity. Autoimmunity results from an imbalance of B – and T-lymphocytes, giving rise to autoantibodies, and is responsible for several disor­ders, such as rheumatoid arthritis (Melikterminas, Ranganath, & Furst, 2008; Yung & Julius, 2008).

A growing body of evidence is pointing to key connections between our immune system and our psychological state. Over 20 years of research shows how our psychological state, or a characteristic such as our attitude, creates neurological, hormonal, and behavioral responses that directly change the immune system and make us more likely to become ill (Irwin, 2008). Psychoneuroimmunology is the