INTRODUCTION AND METHODS
Quality of life of older adults.
Successful aging, (1–65) or maintaining a high quality of life, was proposed by Rowe and Kahn (47) to be composed of three aspects: freedom from disease, engagement with life, and physical and mental competence. High quality of life means that individuals feel better, function better on a daily basis, and for most, live independently. In this article, quality of life is defined by the conceptual framework proposed by Stewart and King (54), and shown in Table 1. In this framework, health-related quality of life is composed of two major domains: functioning (physical, cognitive, and social), and well-being (perceptions of health, emotional function, and self-concept). Quality of life is subjective, and the value of various components differs not only among individuals but within individuals at different stages of life.
The question at hand is whether exercise and/or physical activity (PA) can contribute substantially to an enhanced quality of life for adults who are 65 yr or older, and if so, what levels are necessary to be effective. The goals of exercise and PA are different for young and old adults. For younger adults, exercise is recommended to prevent cardiovascular disease, cancer, and diabetes, and to increase life expectancy. But it is hoped that exercise and PA for the oldest adults can combat the frailty and vulnerability that are caused by inactivity, minimize the biological changes of aging, reverse disuse syndromes, control chronic diseases, maximize psychological health, increase mobility and function, and assist with rehabilitation from acute and chronic illnesses (32).
Methodological limitations in studies of quality of life and dose-response concepts.
Just as the goals of exercise are somewhat different for older adults, the concept of applying exercise dose-response paradigms developed for young adults to those in their 70s and 80s has some difficulties. First, although frequency, duration, and modality can be directly observed and quantified, assessing exercise intensity is problematic in very old adults. High intensities of a dose-response range are associated with health risks and sometimes pain. Second, many physical characteristics other than aerobic capacity, such as denture problems, muscle cramps, loss of tissue pulp in the fingers and soles of the feet, or peripheral neuropathies may preclude accurate measurement of the fitness or strength of older adults. Third, the energy cost of activities with assistive devices (walkers, wheelchairs), joint deformities, and gait disorders may be significantly higher than standard equations would predict (32). Fourth, PA may enhance the quality of life without improving cardiorespiratory status. Just the frequency of exercising may be beneficial in and of itself (54). For example, mood, pain, stiffness, and fatigue may be enhanced by yoga (40). Thus, many researchers have turned to self-report of PA behavior as an alternative to differentiate older adults who may have higher levels of cardiorespiratory capacity, muscular strength, and flexibility as a result of their activity.
The quantification of quality of life is equally fraught with difficulties. Many of the instruments used to assess quality of life have only moderately high reliabilities and uncertain validities. Some are single-item measures, such as, “My health is ‘better than,’ ‘the same as,’ or ‘worse than’ that of other people my age.” Many tests require participants to judge the amount of change in a variable that they think they have experienced. Response bias and cohort differences are problems in items of recall and self-report. Perceptions of intensity are different in older cohorts. Nevertheless, the concept of well-being refers to the way people feel about their life, and investigators have found few ways to study this without simply asking the participants how they feel.
Evidence selection criteria.
A large body of literature exists regarding the relationship of exercise to each of the quality-of-life components shown in Table 1, and a review of all of these would be prohibitive. Therefore, the studies included in this analysis meet the following criteria: a) participants are over 65 yr of age; b) the purpose is to relate different levels of PA or fitness parameters to quality of life outcomes or to disability and dependent living; and c) both quality of life domains, “functioning” and “well-being,” are represented by two or more outcomes. Studies of PA and physical function as the only outcome measure were also included because “. . . a wide variety of behavioral, social, psychological, health status, and demographic risk factors are associated with changes in physical functioning”(27), and it is thought to be composed of several abilities that form the foundation for independent living.
CURRENT STATUS OF KNOWLEDGE
Exercise, physical activity, and well-being.
On the basis of nonrandomized cross-sectional correlational studies, researchers consistently report that measures of physical function in the elderly are related to feelings of well-being (20,37,64). Physical function is an important predictor of social support (64) and predicts the number of face-to-face contacts and the number of sources of instrumental support that older adults have (2) (Evidence Category C). In large prospective studies, both nonrandomized (Table 2) and randomized (Table 3), PA status appears to be related to levels of well-being (40,56,58). Some evidence is available that active older adults have fewer depressive symptoms, but only for the young-old (60–75 yr) and not the oldest-old (76+ yr) (49). Older adults who enthusiastically participated in community-based fitness and sports classes and who adopted a new PA and maintained it for 6 mo reduced anxiety and depression symptoms and increased self-esteem (56). The mirror image of that observation is that older adults who feel good about their emotional functioning may exercise and be more active (31). The evidence for a linkage of PA levels to well-being (36), life satisfaction (56,59), or to measures of control or mastery (51,56), is not always positive (Evidence Category C).
In nonrandomized or uncontrolled studies in which an exercise intervention was applied (Table 4), evidence for a training effect on aspects of well-being was weak. No changes in well-being were reported after 6 mo (11), 9 mo (59), or 1 yr (55). When changes were reported, they were small (9) and occurred only when participants were regrouped post hoc on the basis of the percent of time spent in the training zone (14) (Evidence Category C). Exercise effects on components of well-being were also mixed in the only two randomized control experiments available (Table 5). King (28) reported significant differences in well-being, and in the participants’ confidence of their physical function, after 12 mo, but not 6 months of community-based PA classes. Peel (38) also reported participants’ confidence to be increased, and their emotional function to improve. Conversely, Perrig-Chiello et al. (39) found no improvement or training group differences in well-being, self-efficacy, or control beliefs after 8 wk of resistive training (Evidence Category B). No studies were found that could be categorized as Evidence Category A.
In summary, correlational studies support a relationship between PA and components of well-being, evidence from intervention studies is mixed, and no evidence from truly experimental studies (Evidence Category A) is available. Finally, although almost all investigators assume that habitual exercise may improve psychological well-being, and some intervention studies document this, it may also be true that a strong sense of well-being is necessary to comply with a habitual and intensive exercise program (49).
Exercise, physical activity, and physical function.
Within the health-related quality of life framework, physical function has two components: the physical attributes and capacities underlying movement (cardiorespiratory fitness, strength, muscular power, muscular endurance, balance, and flexibility), and the physical tasks that are necessary for daily function (walking, chair-rising, stair climbing, bending, lifting, stooping, carrying heavy objects, running, and hand function). Many of these tasks are items of the Basic Activities of Daily Living (BADL), and Instrumental Activities of Daily Living (IADL) inventories. In this review, only the relationship of exercise outcomes and PA to the ability to function in the physical tasks of daily living is addressed.
In cross-sectional, correlational studies, exercise and self-reported PA are related to levels of physical function. Exercise is frequently reported to be a positive influence of age-related changes of physical function in these studies (57,27), although Skelton et al. (53) failed to find relationships of self-reported habitual PA to functional ability. In clinical studies where exercise outcomes are quantified, strength (35), fitness (35), and muscular power (1,18) have been related to chair-rising, stair-climbing, and walking. Indeed, leg power accounted for 86% of the variance in walking speed of elderly women according to Bassey et al. (1) (Evidence Category C).
In large sample studies, both randomized and nonrandomized, an exercise effect defined by groups differing in self-reported habitual activity is clearly present (19,45). Correlations between self-reported PA levels (ranging from “none” to “high”) and physical function are many times significant and low-moderate. In one study, the number and size of the correlations were increasingly higher in older and older decades, higher in men than in women, and particularly in walking speed and stair-climbing (19). When energy expenditure was estimated from self-reports of habitual PA, a linear trend emerged across low, moderate, and high daily energy expenditure for walking 10 feet and for grip strength. In addition, those who expended larger amounts of energy daily were more likely to have optimal function in BADL and IADL (65), and those who “never walk at least one mile per week” were 1.56 times more likely to decline in function and become unable to perform ADL and IADLs (33). These relationships between PA and physical function appear to be independent of sociodemographic and baseline health status (Evidence Category C).
Whether a PA group-defined “dose-response” exists, or whether an activity level threshold is operative, is unclear. Reuben et al. (45) are strong advocates that exercise levels, as defined by self-reported physical activities, form a hierarchical scale that correlates positively in a graduated manner with progressively increasing advanced ADLs (45). However, Seeman et al. (51) reported that participation in either moderate or strenuous PA was associated with positive changes in balance, gait, chair-stand, and foot tap. Nevertheless, all studies reviewed in Evidence Category C supported some type of relationship between exercise or PA and physical function in the elderly.
Aerobic training interventions have had some positive effects on walking, but primarily for distance and not for speed (28,55,59), although they have not always been shown to affect functional limitations, functional reach, and moving from a bed to standing. Intensity level of the exercise was not a factor, and differences were most frequently seen when participants in experimental groups were regrouped post hoc into those who worked most in the training zone or who appeared to expend more energy and attend more classes (59). Resistance training was associated with improvements in tasks requiring strength: rising from the floor (kneeling or a chair), or climbing stairs, and not activities associated with endurance, balance, or disability (8) (Evidence Category B). Other investigators failed to observe resistive training improvements in many of the physical function tasks (35). Two of these studies were short in duration (4,53), and in others, it is likely that the participants’ baseline strength was above the sensitivity level of the test so that improvements could not be observed (for details, see Buchner and De Lateur (7)) (Evidence Category C).
Exercise, physical activity, mental function, and engagement with life.
The components of mental function and engagement with life within the quality of life framework have received almost no attention. Although a large body of literature exists on the topic of exercise, PA, and cognition, these studies primarily focus on information processing and executive function and do not address the issues of mental operations necessary for daily function and social interactions in the elderly. Similarly, almost no studies are available in which changes in PA are related to changes in role or social activities, such as volunteer work, community activities, participation in social groups, or in hobbies and recreational pursuits. Scant evidence is available that aerobic training was related to perceived changes in family relations (14) (Evidence Category C), and that participating in a training study resulted in the participants increasing their total activity time after the training program (39,48). However, others found no difference in social or role limitations and no perceived change in social function (38,48) (Evidence Category B).
Physical function and physical activity participation as predictors of independent living.
Results from a set of population-based, cross-sectional and longitudinal studies (Evidence Category C), most of which assessed thousands of older adults over the age of 65 yr, are relatively consistent in their reports of the relationship of PA and/or physical function to independent living. Regular PA and disability are inversely related; PA predicts frailty and health-related disability (30,42,52,58,61). In these studies, persons who were more physically active at baseline were less disabled several years later. Some evidence exists that equal benefits derive from walking, gardening, and vigorous exercise (29).
Physical activity is related to physical function, and function has predicted dependence and relative risk of admission to nursing homes, particularly the functions of walking speed and the ability to participate in outdoor activities (Table 6) (15,22). Low PA levels have been strongly related to physical disability (52,60). In a group of older adults high in PA, all of the odds ratios associated with physical impairment, especially the one-half-mile walk, were <1.00, and a graded response was observed between PA level and impairment. In a smaller, more descriptive study of 27 institutionalized elderly over a 2-yr period, poor performance in grip strength, ambulation, manual ability, and poor cognitive function predicted the transfer to a skilled nursing care facility (60). In addition, regular PA appears to protect the mobility-impaired from further disability (25,29,30,45). Thus, even in individuals with chronic disease, those who expend more energy in physical activities on a systematic basis are more likely to have optimal physical function (65).
A potential risk factor that has been neglected in most programs designed to postpone disability and dependence is that of hand function. From grip strength tertiles at baseline, 26 yr later a gradient of increasing risk emerged for all functional limitations and disability outcomes (42). Hand function on coordination tests increased the ability to differentiate dependent living status from 68% (which was determined on the basis of demographics), to 74%(15). Grip strength may be a marker of habitual PA.
- 1. Ensure that if possible, every participant in an exercise intervention group actually experiences a treatment effect.
- 2. Report effect sizes in intervention studies. Results of experimental studies cannot be compared very well without effect sizes.
- 3. In intervention studies, match the participants’ ability level and the training modality to the task requirements.
- 4. Establish norms for assessment of walking speed at a standardized distance, so that factors influencing walking speed can be compared across studies.
- 5. Develop a standard method of quantifying PA that is feasible to use with moderately large and disparate samples, and encourage its use by all researchers.
FUTURE RESEARCH PRIORITIES
- 1. Determine the effectiveness of introducing PA at various ages in life in preventing, delaying, and/or reversing functional dependence. The question is not whether a lifetime of PA can postpone disability, but whether the benefits are diminished with advancing age, and if so, how much.
- 2. Study the relationship of muscular strength and power to physical function. If this relationship is curvilinear rather than linear, characterize that relationship and determine threshold values, below which function is greatly impaired.
- 3. Determine whether the relationships between PA levels and physical function differs for men and women, and if so, in what ways. Gender factors associated with changes in physical function may be substantial (19,57) and should be clarified.
Address for correspondence: Waneen W. Spirduso, Department of Kinesiology and Health Education, The University of Texas at Austin, Austin, TX 78712; E-mail: Spirduso@mail.utexas.edu.
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