Definition Quality of Life and Measurement

‘‘Quality of life’’ (QOL) subsumes two distinct domains in gerontological research. One is health-related quality of life (HRQOL); the other, nonhealth or environment-based quality of life (Spilker and Revicki). HRQOL encompasses domains of life directly affected by changes in health. Jaschke and colleagues provide a good thumbnail test of whether a domain falls within the category of health-related QOL. In their view, HRQOL domains are aspects of life that improve when a physician successfully treats a patient. A clinically significant change in HRQOL is indicated by a decline in a domain that leads a physician or health care provider to alter a medication or medical treatment. HRQOL domains minimally include functional status (e.g., whether a patient is able to manage a household, use the telephone, or dress independently), mental health or emotional wellbeing (e.g., depressive symptoms, positive affect), social engagement (e.g. involvement with others, engagement in activities), and symptom states (e.g., pain, shortness of breath, fatigue). These domains represent typical outcomes in medical and social science research.

Non-health-related QOL domains include features of both the natural and the created environment (i.e., economic resources, housing, air and water quality, community stability, access to the arts and entertainment) and personal resources (i.e., the capacity to form friendships, appreciate nature, or find satisfaction in spiritual or religious life). These factors affect health-related QOL but, unlike health-related QOL domains, are less likely to improve with appropriate medical care.

The two components of QOL need to be kept separate. First, non-health-related QOL can be viewed as causally prior to or as a determinant of HRQOL. Components of non-health related QOL (i.e., social support, economic resources, religion, and housing) may affect HRQOL outcomes, such as social integration and functional and emotional well being. Second, non-healthrelated QOL is more heterogeneous, with less consensus about the range of domains that should be included in the measure. For example, no one would suggest that severe abdominal pain is preferable to a runny nose; most would agree that the runny nose is associated with a better health-related QOL state. Consensus of this sort is harder to establish for spirituality, friendship, or access to the arts.

It is valuable to obtain information on both kinds of QOL because economic and social status affect HRQOL, and both are necessary to understand health-related outcomes. However, more emphasis has been placed on the study of HRQOL for several reasons. First, older people are at risk for chronic conditions, and effective disease management in large part consists of finding treatments that minimize the QOL impact of disease. Second, HRQOL measurement is further advanced than measurement of non-health-related QOL. Finally, while housing, air quality, and other components of the environment are clearly important features of QOL, they are important mainly because of their effect on health and health-related QOL (Albert). On the other hand, Lawton states that the two are sometimes hard to separate; for example, successful treatment by a physician may improve one’s capacity to make friends.

Health-related QOL emerged from research on health status. Early measures, such as the Sickness Impact Profile (SIP) (Bergner, et al.), sought to identify common domains affected by disease that would allow clinicians to gauge the impact of a clinical condition. The SIP identified twelve health-related QOL domains, which include ambulation, mobility, body care and movement, communication, alertness behavior, emotional behavior, social interaction, sleep and rest, eating, work, home management, and recreation. A key element of the SIP, and of almost all QOL measures since, has been that patients themselves rate their level of impairment. This subjective element is the essential feature of health-related QOL, for who can better report on the QOL impact of a medical condition than the patient (Gill and Feinstein)? Indeed, health-related QOL is sometimes called ‘‘patient-reported outcomes’’ to stress this subjective focus. Of course, the focus on self-reported status is problematic for people with cognitive disorders, such as Alzheimer’s disease, who may be unable to comprehend questions about their status. QOL measurement for such populations may require simplified questionnaires, use of proxy reports, or observational measures (Albert and Logsdon).

A second source for the current interest in health-related QOL is its potential significance for economic evaluation of medical therapeutics and technologies. The goal of economic studies of HRQOL has been to assign values to health states. To return to an earlier example, an economic approach to HRQOL asks how much worse ‘‘severe abdominal pain’’ is than ‘‘runny nose.’’ Suppose two numeric anchors are established: 1.0 for the state of no symptoms/no daily limitations and 0.0 for death (recognizing, however, that some people consider certain health states, such as coma or intractable pain, as states worse than death). Kaplan’s Quality of Well-Being/General Health Policy Model subtracts 0.17 for the state of ‘‘runny nose’’; thus, someone with a runny nose is at about 83 percent of optimal health. ‘‘Sick or upset stomach, vomiting’’ is associated with a score of -0.29; someone with the condition would be at 71 percent of optimal health. These numerical ratings, derived from respondents who rated descriptions of a wide variety of health states, confirm people’s intuitions and offer one way to establish how much worse one clinical state is relative to another in terms of HRQOL.

An alternative tradition in QOL measurement avoids the assignment of numeric values to health states. This tradition relies on naturally occurring indicators of impairment or disability. Thus, Sullivan developed an early index based on living arrangement (nursing home or community), mobility impairment, ability to perform major age-appropriate roles (school, work, home maintenance, personal self-maintenance), and limitation in usual, daily activities. From this classification emerged five QOL states, ranging from institutional residence to community residence without disability or limitation in daily activities. Similarly, the Behavioral Risk Factors Surveillance System used by the Centers for Disease Control relies on reports of ‘‘not good health days,’’ days when a component of health is adversely affected (Hennessey, et al.). Respondents are asked, ‘‘Thinking of the past 30 days, how many days were there when your physical health was not good?’’ Other questions ask about mental health, sleep, energy, anxiety, and related domains.

Introduction of a QOL focus in research on aging was pioneered by Katz and colleagues, and by Lawton and Brody, with a focus on functional status and behavior, which is now universal in gerontology and geriatrics. Lawton and Brody summarized a QOL emphasis for care of older people, thus: ‘‘Function and behavior, rather than diagnosis, should determine the service to be prescribed.’’ The common, final pathway of different diseases is their impact on functional ability and other domains of QOL; thus, the focus in later life should be development of strategies, both clinical and environmental, to minimize these effects and to work with the strengths older people continue to retain.

However it may be measured, health-related QOL declines with age. This is a central, inescapable consequence of the increased life span and consequent increased prevalence of chronic disease and the effects of senescent changes in many physiologic systems. Senescence, apart from disease, is evident in declines in working memory, psychomotor speed, touch sensibility, vision, and hearing; loss of skeletal muscle and strength; and reduction in joint range of motion. These changes affect HRQOL; for example, pain in arthritic joints leads to circumscription of choice in daily activities; lower-extremity weakness means difficulty climbing stairs or standing up long enough to prepare a meal; and slowing of psychomotor skills may mean inability to drive safely. Older people adjust their daily lives to accommodate these decrements and in this way preserve HRQOL. Still, cross-sectional studies show major declines in health-related QOL with increasing age. For example, mean health-related QOL scores for the U.S. population (with 1.0 optimal health and 0.0 death) ranged from 0.90 to 0.94 for people under age thirty, 0.81–0.90 for people age thirty-five–sixty, 0.70–0.79 for people aged sixty–eighty, and 0.51–0.63 for people over age eighty (Erickson, et al.). By this formulation, a medical intervention that improved health-related QOL from 0.74 to 0.81 would therefore be equivalent to a reduction in age, in this case from seventy–seventy-five to fifty-five–sixty. Thus, clinical trials for medical interventions and therapeutics have increasingly turned to health-related QOL as an outcome to capture the broad effects of treatment.

In contrast to health-related QOL, environmental or non-health-related QOL may remain high throughout life or even improve with greater age. With retirement, for example, older people have more leisure time; and with children gone, houses paid for, and successful investments, they may have more disposable income. As a result, older people have more opportunities to develop interests and create satisfying environments. Better health care and effective disease management also play a major role in fostering QOL in late life. These factors counterbalance declines in health-related QOL and may be responsible for the great resiliency older people show in the face of declining health and death.

In short, health-related and environment-based quality of life must be distinguished. The former is linked to age and shows clear decline across the life span, due in large part to senescent processes and to increased susceptibility to chronic disease. The latter is not as strongly related to age, and older people can build environments that promote QOL. The two come together in older people’s ability to modify environments in ways that limit the QOL impact of poor health.