Assessment of physiologic competence and health status in humans, at any age, is a multifactorial process that requires quantitative measurements of numerous parameters at progressive ages (Fig. 6) (34). Assessment must reflect the different variables that influence the age-related timetables for key bodily systems, combine them to represent a cohesive health profile of the individual, and satisfy a number of criteria:
■ The variables must be indicative of a function important to the competence or general health of the individual and capable of influencing the rate of aging.
■ They must correlate with chronological age.
■ They must change sufficiently and with discernible regularity over time to reveal significant differences over a three- to five-year interval between tests.
■ They must be easily measurable in an individual or cohort of individuals without hazard, discomfort, or expense to the participant, or excessive labor or expense for the investigator.
The validity of any assessment lies in the choice of the proper test or battery of tests best qualified to provide an overall picture of current health and to eventually serve as a basis for prediction of future health and length of the life span. Such a choice is complicated by the need to also take into account the financial feasibility and the facilities available for the testing. The relatively large number of tests for assessing physiologic competence and health status in the elderly reflects the current failure to reach a consensus on the best checklist. A global measure of physiologic status may be derived from many different combinations of tests. Selection will depend on the purpose of the assessment and who will use these data. With respect to purpose of assessment, measurements may be expected to
■ describe the functional status of an individual at progressive chronologic ages,
■ screen a selected population for overall physiologic competence or competence of specific functions using cross-sectional or longitudinal sampling methods (Chapter 1),
■ monitor the efficacy of specific treatments, drugs, exercise, and diet, and
■ predict persistence or loss of physiologic competence to determine incidence of disease and to evaluate life expectancy.
Approximately 10% of nondisabled community-dwelling adults aged 75 and older lose independence each year. A number of simple qualitative and timed performance tests may be useful in identifying subgroups of older persons who are at increased risk for functional dependence, for example, are unable to perform activities of daily living (ADLs) and instrumental activities of daily living (IADLs) (see below) (35,36).
The choice of tests will depend on whether the user is a health provider, specialist, researcher, or case manager. Even with a precise identification of the nature of the assessment needed and of the user who needs it, it still remains difficult to choose the most significant and feasible tests. Some tests, although relatively innocuous in young and healthy individuals, may be troublesome for the elderly. In addition, some of the tests depend on the self-awareness of the individual tested, and her/his responses often overevaluate or underevaluate the symptoms (Box 1). Yet, it may be contrary to the interest of the elderly to assert that they represent a vulnerable group needing special protection. Rather, benefits may accrue for the elderly from their participation in medical and psychosocial survey research. Not only may such tests lead to the discovery of an unsuspected illness and its eventual treatment, but they may also provide altruistic commitment and mental satisfaction.
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For centuries, ever since the legendary Ponce de Leon went searching for the elusive Fountain of Youth, people have been looking for ways to slow down the aging process. Medical science has made great strides in keeping people alive longer by preventing and curing disease, and helping people to live healthier lives. Average life expectancy keeps increasing, and most of us can look forward to the chance to live much longer lives than our ancestors.