4 - Multifactorial Memory Training in Normal Aging: In Search of Memory Improvement Beyond the Ordinary
Editors: Backman, Lars; Hill, Robert D.; Neely, Anna Stigsdotter
Title: Cognitive Rehabilitation in Old Age, 1st Edition
Copyright 2000 Oxford University Press
> Table of Contents > Part III - The Influence of Health and Health Behaviors on the Rehabilitation of Cognitive Processes in Late Life > 7 - The Role of Physical Exercise as a Rehabilitative Aid for Cognitive Loss in Healthy and Chronically III Older Adults
7
The Role of Physical Exercise as a Rehabilitative Aid for Cognitive Loss in Healthy and Chronically III Older Adults
Charles F. Emery
Older adults are frequently encouraged to participate in physical exercise due to the cumulative evidence indicating physiological benefits of exercise such as enhanced cardiovascular function, physical stamina, and muscle strength (Aniansson, Grimby, Rundgren, Svanborg, & Orlander, 1980; Pyka, Lindenberger, Charette, & Marcus, 1994), weight loss (Evans & Cyr-Campbell, 1997), prevention of osteoporosis (Bachmann & Grill, 1987), and enhanced glucose metabolism (Raz, Hauser, & Bursztyn, 1994). In addition, data suggest that exercise among older adults may be associated with improved quality of life (Singh, Clements, & Fiatarone, 1997), reduced psychological distress (McMurdo & Rennie, 1994), and improved neuropsychological or cognitive performance (Dustman et al., 1984). The potential for exercise-related improvements in cognitive functioning is of particular interest due to the increased prevalence of cognitive deficits among older adults and the widespread inclusion of exercise programs for older adults in a variety of settings (e.g., senior centers, assisted-care living facilities, hospital inpatient units, rehabilitation settings). The purpose of this chapter is (a) to describe briefly the age-related physical and cognitive changes that have been a focus of research in this area, (b) to discuss the physical and cognitive changes associated with exercise among older adults, and (c) to describe the relevance of these research findings for cognitive rehabilitation among older adults.
Age-Related Changes in Physical and Cognitive Functioning
Physical Functioning
Cross-sectional data indicate numerous age-related changes in physical functioning such as decreases in cardiac output and heart rate (Strandell, 1976), and reduced
P.124
maximal oxygen consumption (VO2max; Buskirk & Hodgson, 1987; Ehsani, 1987). VO2max has been shown to decline approximately 10% each decade after age 25, and the decline may increase to nearly 20% in the seventh decade. Other physiological changes include reduced lung volume and poorer clearance of mucus from the lungs (Mahler, Rosiello, & Loke, 1986), as well as changes with age in the protein and mineral balance of the skeleton, increasing the risk of osteoporosis and bone fractures (DiGiovanna, 1994). Hormonal changes include diminished growth hormone production and decreased sensitivity to insulin (Rudman et al., 1981).
It has been suggested that at least some of the physiological changes associated with age may contribute to the well-documented decreases in cognitive performance associated with age and with disease among older adults. In particular, diseases of the cardiovascular and pulmonary systems may be associated with inadequate circulation and hypoxia, contributing to neuronal degeneration and, ultimately, diminished cognitive function (Spirduso, 1980).
Cognitive Functioning
Cognitive changes in markers of so-called fluid intelligence, such as reaction time and problem-solving ability, have been widely investigated. Age-related slowing of information-processing speed (Salthouse, 1991) and decreased memory performance (Craik & Jennings, 1992) are reflected in impaired performance among older adults on neuropsychological tests of reaction time, psychomotor/sensorimotor performance, visuospatial problem solving, attention and concentration, memory, and executive function (Lezak, 1995). In addition, neurophysiological indicators such as event-related potentials (ERPs) and electroencephalograms (EEGs) reflect slowing of brain signal processing with age (Prinz, Dustman, & Emmerson, 1990).
Physiological Changes Associated With Long-Term Exercise
The benefits of long-term exercise for physiological functioning include slower decline in muscle cell thickness, number of muscle cells, and muscle strength (Pyka et al., 1994). Also, exercise inhibits the gradual increase in fat accumulation, and older adults with a long-standing pattern of exercise may maintain higher levels of high-density lipoproteins (HDL) than sedentary older adults (Nieman et al., 1993; Tamai et al., 1988). These blood lipid factors contribute to exercise being associated with decreased risk of hypertension, atherosclerosis, coronary heart disease (CHD), and stroke. The most widely accepted standard for evaluating exercise capacity is VO2max. Although VO2max is known to decline with age, longitudinal studies suggest that regular physical exercise may attenuate this decline (Bruce, 1984; Kasch, Wallace, & Van Camp, 1985), with exercise training programs among older adults often reporting increases in VO2max of from 15% to 25%. In turn, exercise may contribute to decreases in maximum heart rate required for maximal activity, as well as increases in stroke volume and cardiac efficiency (Tate, Hyek, & Taffet, 1994). Because measurement of VO2max is the gold standard for determining cardiovascular fitness during a standardized exercise stress test, usually either a treadmill or a bicycle ergometer, studies in which fitness levels are assessed with VO2max can more readily be used to
P.125
evaluate the association of physical exercise with cognitive function. In the absence of VO2max data, it is difficult to ascribe changes in cognitive performance to physical fitness levels.
Physical exercise has been investigated as a means of addressing age-related changes in physiological and cognitive functioning. Although the mechanisms by which exercise affects physiological functioning are well documented (Bouchard, Shephard, Stephens, Sutton, & McPherson, 1990), the mechanism of exercise effects on cognitive function is controversial. Several theories have been proposed to explain the mechanism by which exercise may affect cognitive performance. Most theorists suggest that exercise benefits cognitive functioning via improvements in cardiovascular efficiency, although central nervous system changes and reduced affective distress also are implicated.
Theoretical Bases for the Influence of Exercise on Cognitive Function
There are four dominant theories in the literature pertaining to exercise effects and cognitive function. First, early theorists suggested that exercise contributes to aerobic capacity and cerebral circulation and enhances functioning of the neurons that activate muscle fibers (Spirduso, 1980). It has been thought that diseases of aging, such as cardiovascular disease, contribute to inefficient cerebral circulation and reduced oxygenation of the brain. According to this model, decreased blood flow in the brain is associated with diminished oxygenation of the brain, which, in turn, is associated with diminished brain function. The mechanism responsible for diminished brain function is not total cerebral blood flow, which would not be expected to change, but regional cerebral blood flow. In theory, exercise would be likely to increase regional cerebral blood flow to specific brain areas, including prefrontal, somatosensory, and primary motor cortex (Spirduso, 1980). Exercise would thus be expected to attenuate the naturally occurring reductions in blood flow to specific brain areas. Consistent with this theory, it has been suggested that increased availability of oxygen in the brain with exercise contributes to metabolism of neurotransmitters, especially acetylcholine, dopamine, norepinephrine, and serotonin, which, in turn, are associated with changes in neurophysiological and neuropsychological functioning (Dustman et al., 1984, 1990). Availability of circulating glucose in the bloodstream would be associated with fitness level and would enhance higher level cognitive processes (Elsayed, Ismail, & Young, 1980). In support of this general hypothesis, it has been found that treatment with pure oxygen is associated with significant improvement in neuropsychological functioning among older adults with memory problems (Jacobs, Winter, Alvis, & Small, 1969) and among hypoxemic patients with chronic obstructive pulmonary disease (Heaton, Grant, McSweeny, Adams, & Petty, 1983).
A second broad theory suggests that physical exercise increases physical and mental arousal, which, in turn, contributes to attentional processes that are central to cognitive performance. In this model, it is suggested that exercise may facilitate attentional processes initially by enhancing central nervous system function. The nervous system arousal required for engaging in physical exercise is thought to facilitate other brain functions as well (Powell, 1974). However, as the intensity or duration of the exercise
P.126
increases, muscular fatigue then may eliminate the facilitative effects of the early arousal (Tomporowski & Ellis, 1986).
A third theory posits that because cognitive functioning may be impaired in individuals who are depressed or anxious (Horn, Donaldson, & Engstrom, 1981; Kennelly, Hayslip, & Richardson, 1985), improved cognitive functioning may result from enhanced psychological well-being following exercise.
Fourth, it has been suggested that because sympathetic hyperarousal is associated with impaired performance on tests of cognitive functioning, the reduction in sympathetic tone accompanying chronic exercise may contribute to improved cognitive performance (Eisdorfer, Nowlin, & Wilkie, 1970).
Emanating from this theoretical background and from the applied interest in exercise interventions, numerous studies and clinical programs have been developed to evaluate physical exercise training among older adults.
Types of Exercise Studies
Past studies of exercise among older adults can be categorized in four ways:
Early cross-sectional studies evaluated cognitive performance among existing groups of self-reported exercising or nonexercising older adults. These studies are limited by a selection bias, since exercise patterns in such studies can not be manipulated experimentally.
Most studies in the literature have evaluated outcomes of exercise interventions lasting anywhere from several weeks to 1 year or more. Such studies of chronic exercise outcomes can address the extent to which exercise contributes to cumulative outcomes over time, as may be found with a parameter such as VO2max during exercise, which would be expected to improve gradually over time. These studies address the issue of whether cognitive benefits of exercise accrue over time.
A small number of studies have been conducted evaluating outcomes of a single bout of exercise. These studies of acute exercise effects are useful for examining responsiveness to exercise on a parameter such as blood pressure, which would be expected to respond immediately to exercise activity. Studies of this type indicate the extent to which cognitive changes occur immediately following a single bout of exercise.
Although most of the past research has been conducted with samples of healthy older adults, recent studies have also evaluated cognitive outcomes of exercise among older adults with chronic illness.
These four broad categories of studies will be used as a framework for discussing the effects of exercise on cognitive performance among older adults.
Cross-Sectional Studies of Exercise and Cognitive Performance
Early studies of exercise and cognitive function among older adults evaluated reaction time speed as an indicator of cognitive performance. A classic study in this area was conducted by Spirduso (1975), who categorized adult men by age (younger = 20 30 years vs. older = 50 70 years) and by physical activity level (active vs. inactive, according
P.127
to self-reported regular racket-sport involvement at least three times a week). Results indicated that older inactive subjects were significantly slower in simple reaction time and movement time than were inactive younger subjects or than active subjects of either age group. Using a similar methodology among women, Rikli and Busch (1986) found that older inactive women (age = 68.9 years) had slower choice reaction time performance than did older active women (age = 68.7 years; defined as those who participated in aerobic exercise at least three times a week), but that activity level did not distinguish performance among younger women (age = 21 22 years). More recent cross-sectional data suggest that older active men (as defined by self-reported exercise activity) demonstrate significantly better performance than older sedentary men in performance on a coding task requiring visuospatial processing (Stones & Kozma, 1989), and that visuospatial performance is associated with fitness level (as measured by predicted VO2max) among older men, but not among middle-aged or younger men (Shay & Roth, 1992). The latter study found no fitness effects for performance on cognitive tasks measuring attention and concentration, verbal memory, or sensorimotor performance. However, Clarkson-Smith and Hartley (1989) found that older adults (mean age = 67 years) categorized as high exercisers (based on self-report of overall activity level) performed better than low exercisers (mean age = 72 years) on measures of reasoning, working memory, and reaction time. Dustman and colleagues (1990) evaluated neurophysiological endpoints (e.g., electroencephalogram, event-related potential, visual sensitivity) among young (20 31 years) and old (50 62 years) men, who were categorized as high fit or low fit (by use of VO2max from an exercise test). Results indicated that high-fit subjects had better neurocognitive performance, enhanced visual sensitivity, and shorter ERP latency regardless of age.
Summary
The data from these cross-sectional studies strongly support the notion that self-reported exercise behavior and/or physical fitness is associated with enhanced performance on cognitive tasks assessing psychomotor performance, visuospatial performance, and reasoning. These fitness differences are generally supported by the data from neurophysiological brain studies, although results on visual sensitivity (as assessed by Critical Flicker Fusion threshold) were equivocal, with one study finding a fitness effect (Dustman et al., 1990) and one study finding no effect (Shay & Roth, 1992). There is no support for the notion that exercise activity is associated with enhanced performance on cognitive tasks requiring attention and concentration, and there is only limited support for an association of exercise with memory. The results are limited by self-selection factors, since subjects were not randomly assigned to conditions. In addition, most of these studies relied on self-report of exercise activity level, without more objective documentation of fitness level. Only Dustman et al. (1990) utilized a maximal exercise stress test to categorize subjects into fitness groups, and Shay and Roth (1992) used predicted VO2max for categorizing subjects. Although self-reported exercise activity is appealing from a practical standpoint, it presents a confound for determining the relationship between physical fitness and cognitive performance, since self-reports may be biased by many factors including social desirability, education, and socioeconomic status.
P.128
Effects of Chronic Exercise on Neuropsychological Functioning
Physical Exercise Interventions
Exercise conditioning programs for older adults typically include aerobic exercise as a foundation. Aerobic exercise requires oxygenation of the muscle cells for metabolism of free fatty acids into energy for muscle contractions and is characterized by the rhythmic movement of large muscle groups, as occurs in activities such as walking, running, bicycling, and swimming. Exercise interventions for older adults also may include anaerobic exercise, such as strength training with weights or elastic bands. Anaerobic exercise requires a high physical work level, which leads to muscular fatigue and limits the duration of the activity. Most researchers and clinicians agree that the cardiorespiratory benefits of exercise will be achieved with a program of exercise lasting at least 8 weeks, with 1-hour exercise sessions two to three times per week. Exercise sessions typically begin with a brief 5- to 10-minute warm-up period, during which participants engage in muscle-stretching exercises to enhance range of motion and prepare the muscles for more intensive exercise. This warm-up is followed by 20 40 minutes of aerobic exercise (or 20 30 minutes of anaerobic exercise), and exercise is completed with a 5- to 10-minute cool-down period during which participants engage in further muscle-stretching exercises while allowing heart rate to return to resting levels.
Cognitive Outcomes of Exercise
Previous studies examining the effects of physical exercise interventions on neuropsychological functioning have produced conflicting results. Early studies suggested a positive association of exercise with enhanced cognitive functioning. Powell (1974) found enhanced performance on the Progressive Matrices Test and Wechsler Memory Scale associated with exercise in a study of 30 institutionalized older adults (mean age = 69.3 years) randomly assigned to exercise, social activity, or a waiting-list control group for 12 weeks. In addition, three observational studies (i.e., with nonrandomized groups) have examined exercise outcomes and cognitive performance. Elsayed et al. (1980) examined the effects of exercise on fluid intelligence (i.e., concept formation, reasoning, and abstract thinking) and crystallized intelligence (i.e., learned information), as measured by the Culture Fair Intelligence Test, among subjects who were initially divided into four groups: high-fit/young, high-fit/old, low-fit/young, and low-fit/old. All subjects attended three sessions of exercise (90 minutes per session) for 4 months. At the end of 4 months, all groups scored higher on the fluid intelligence measures. Across groups, younger subjects scored better than older subjects, and high-fit subjects scored better than the low-fit subjects. In a study of older adult (mean age of two groups = 58 and 62 years) exercise participants at a fitness club (Stacey, Kozma, & Stones, 1985), 6-month follow-up data indicated enhanced performance on a reaction time task and on the Digit Symbol test of the WAIS-R. However, neither of the latter studies included nonexercise controls; thus, improved performance may have reflected practice effects. Perri and Templer (1984 1985) compared memory performance (as measured by the Rey Auditory Verbal Learning Test) of a nonrandomized
P.129
control group of 19 nonexercising subjects (mean age = 65.3) with that of 23 subjects participating in a 14-week exercise program (mean age = 65.6). Results indicated no effect of exercise on short-term or long-term memory.
Several larger scale randomized studies have been conducted evaluating psychological well-being and neuropsychological functioning of older adults, as shown in Table 7.1. Dustman and colleagues (1984) conducted one of the first randomized studies of community-residing older adults, with documented exercise training effects, demonstrating significant cognitive improvement associated with aerobic exercise. They observed an impressive 27% increase in VO2max among exercise subjects. A recent study by Williams and Lord (1997) found significant benefits of exercise for reaction time and short-term memory. Although this study was impressive in its inclusion of a large sample of women followed over a 12-month period, the study did not evaluate VO2max, and there was a high degree of variability in adherence to the exercise program. Thus, it is difficult to attribute cognitive changes directly to exercise conditioning.
In addition, two large-scale, randomized studies have revealed negative results. Blumenthal and colleagues (1989) found relatively few changes associated with aerobic exercise among 101 older men and women, despite a 12% increase in VO2max. Because experimental and control groups improved on several of the neuropsychological measures, results were attributed to practice effects rather than to the exercise intervention. Exercise also was not associated with improved reaction time performance in this study (Madden, Blumenthal, Allen, & Emery, 1989), and after a 14-month follow-up, improvement in neuropsychological functioning was attributed to practice effects rather than to exercise effects (Blumenthal et al., 1991). Similarly, a 12-month exercise intervention conducted by Hill, Storandt, and Malley (1993) failed to find improvement on cognitive measures assessing memory, psychomotor speed, and attention, despite a significant 23% improvement in fitness level in the exercise group.
Six additional studies suggest that exercise interventions have minimal influence on cognitive performance among healthy older adults (Emery & Gatz, 1990; Hassmen, Ceci, & Backman, 1992; Molloy, Richardson, & Crilly, 1988; Okumiya et al, 1996; Panton, Graves, Pollock, Hagberg, & Chen, 1990; Stevenson & Topp, 1990), as shown in Table 7.1. Five of these studies were conducted with community-residing healthy older adults, and only the Molloy et al. study was conducted with institutionalized women. Although the study by Okumiya et al. indicated significant improvement on two of the neurobehavioral measures, neither test reflected specific cognitive functions (i.e., one test reflected physical mobility; the other, balance).
Summary
Early studies indicated improved cognitive performance associated with exercise interventions, but more recent studies have indicated minimal effects of exercise on cognitive function. Two exceptions are the studies by Dustman et al. (1984) and Williams and Lord (1997). The positive results of the Dustman et al. study may stem from inclusion of a relatively younger sample and a very large increase in VO2max. The Williams and Lord results are countered by those of Hill et al. (1993), who studied subjects over a similar (12-month) time frame and found no cognitive effects. Allthough
P.130
P.131
the Williams and Lord results are limited by the absence of VO2max data, the inclusion of only women in their study may suggest gender effects that could warrant further exploration.
Table 7.1. Selected Randomized Intervention Studies of Exercise Effects on Cognitive Function Among Older Adults | ||||||||||||||||||||||||||||||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| ||||||||||||||||||||||||||||||||||||||||||||||||
Acute Exercise Outcomes
It has been suggested that acute bouts of exercise initially may facilitate attentional processes by directly stimulating the central nervous system (Tomporowski & Ellis, 1986). However, this facilitative effect then may be counteracted by muscular fatigue. Thus, in theory, an individual's level of physical fitness would have an impact on neuropsychological changes following an acute bout of exercise (Tomporowski & Ellis, 1986). An interaction effect has been observed among younger subjects, wherein physically fit individuals improve more than less fit individuals on cognitive measures following acute exercise (Gutin, 1966; Gutin & DiGennaro, 1968). Few studies have examined the acute effects of exercise, and most of the extant studies have been conducted with college-age subjects. However, two relatively recent studies of older adults help illustrate both the strengths and the weaknesses of research in this area. Molloy, Beerschoten, Borrie, Crilly, and Cape (1988) examined acute effects of a 45-minute exercise session on mood and cognitive functioning of 15 older adults (mean age 66) who had complained of memory loss or cognitive impairment. The exercise condition consisted of a 5-minute warm-up, 20 minutes of light aerobic exercise (walking or playing games), and 15 minutes of stretching exercises. The control condition consisted of watching another subject participate in the exercise condition. The study was counterbalanced, with all subjects participating in both the exercise and the control conditions, and a period of 1 week separated each testing session. Assessments included measures of memory, problem solving, and verbal fluency, and results indicated improvement in logical memory (from the Wechsler Memory Scale) and in scores on the Mini-Mental State Examination.
Emery, Honn, Becker, and Frid (1996) conducted a study of acute exercise effects and cognitive function among 24 older (mean age = 68.6) men and women. Each subject participated in 20 minutes of exercise on a stationary bicycle and 20 minutes of watching a videotape about exercise, with assessments of cognitive function (psychomotor speed, memory, executive function) before and after each condition. Order of conditions was randomly assigned to subjects, and participation in each condition was separated by 1 week. Results indicated improved cognitive performance associated with both conditions, suggesting practice effects rather than exercise effects.
Summary
No additional published studies have examined acute effects of exercise on cognitive function, although several other studies have evaluated emotional changes associated with acute bouts of exercise. The methodological limitations of studies in this area (e.g., small sample size, confounding practice effect due to repeated measures occurring in short time interval, potential for regression to the mean when subjects enter the study complaining of memory problems) may restrict the conclusions that can be drawn. However, this methodology may be promising for further evaluation of mechanisms
P.132
by which exercise is associated with cognitive function. Cognitive changes occurring acutely would be more likely to support an arousal model of exercise effects, but changes occurring following an intervention would be more likely to support a model of cardiovascular fitness as a critical factor.
Exercise Effects Among Chronically Ill Older Adults
Increased life expectancy in recent decades has meant that greater numbers of older adults are afflicted with chronic, physically debilitating illnesses, including chronic obstructive pulmonary disease (COPD), arthritis, hypertension, and Alzheimer's disease. Often exercise is an integral aspect of rehabilitation programs for such individuals, and the data available from exercise rehabilitation programs, although limited, suggest positive cognitive outcomes.
Lung Disease
Patients with COPD generally suffer from long-lasting reductions of blood oxygen (PaO2), and it has been suggested that chronic reduction of PaO2 also significantly contributes to cognitive deficits (Fishman & Petty, 1971). In studies of hypoxemic patients, deficits in simple motor skills and concentration were found (Grant, Heaton, McSweeny, Adams, & Timms, 1982), although language and memory were relatively unaffected, and neuropsychological impairment was associated with low levels of blood oxygen. Prigatano, Parsons, Wright, Levin, and Hawryluk (1983) concluded that the most likely explanation for impaired cognitive functioning in COPD patients is either (a) lower levels of blood oxygenation, leading to inefficiencies in neural functioning, or (b) COPD contributing to increased vascular disease, which, in turn, leads to reductions in cerebral blood flow and oxygen consumption. In either case, among COPD patients, the primary source of cognitive deficits appears to be directly related to blood oxygen levels. Further support for this hypothesis comes from studies in which continuous oxygen treatment reversed impairments among COPD patients on measures of visuospatial function and simple motor movement (Krop, Block, & Cohen, 1973).
In a recent study, Emery, Schein, Hauck, and Maclntyre (1998) evaluated the effects of exercise on psychological well-being and cognitive functioning among 79 older adults (mean age = 66.6 6.5) with COPD. Subjects were randomly assigned to an exercise condition (exercise, education, and social support), an education condition (education and social support), or a waiting-list group during a 10-week intervention period. The exercise component included walking, strength training, and bicycle ergometry training. The cognitive assessments (attention, motor speed, mental efficiency, and verbal processing) conducted before and after the intervention period indicated that subjects in the exercise condition improved significantly on the measure of verbal processing showing self-control and self-monitoring characteristic of executive cognitive functions. Subjects in the two control groups manifested no change on this measure. Thus, the study offers preliminary evidence of cognitive benefit of exercise among COPD patients participating in exercise rehabilitation and suggests that improvement in executive cognitive function resulted from changes in neural processing.
P.133
Heart Disease
Age-related increases in the incidence of cardiovascular disease have been attributed, in part, to deconditioning and inactivity (Bortz, 1982). In turn, patients with coronary heart disease (CHD) may be at risk for cerebral infarction or hemorrhage. Deterioration of the cardiovascular system associated with arteriosclerosis and heart disease may reduce cerebral blood flow and thus result in decreased cerebral oxygen consumption. A relatively high incidence of cognitive deficits has been observed in one past study of medically stable cardiac inpatients (approximately 20% of the sample) despite the absence of neurological deficits (Garcia, Tweedy, & Blass, 1984), and cognitive deficits have been observed among cardiac rehabilitation patients following cardiac surgery (Robinson, Blumenthal, Burker, Hlatky, & Reves, 1990). Although the nature and extent of postsurgical cognitive deficits varies widely across studies, the deficits are thought to result from intraoperative microemboli or hypoperfusion, and they may resolve spontaneously over a period ranging from several days to several months. However, in a cardiac rehabilitation setting, Barclay, Weiss, Mattis, Bond, and Blass (1988) observed mild to moderate cognitive impairment among 70% of 20 clinically stable older (mean age = 72.5 2.1 years) patients. A large proportion of the sample (35%) was impaired to such a degree that they were unable to self-administer medications appropriately. Thus, cognitive impairment among cardiac patients may range from mild difficulty on standardized tests of attention and concentration, to more significant memory deficits, to very significant difficulty with activities of daily living (ADLs) such as medication use.
Exercise studies of patients with coronary artery disease (CAD) have also been conducted, but only one study has been conducted with older cardiac patients. Satoh, Sakurai, Miyagi, and Hohshaku (1995) studied walking behavior among 46 mostly female (76%) older (ago > 70 years) Japanese cardiac patients. All subjects had a history of myocardial infarction (MI) or arrhythmia, but none had cerebrovascular disease. Subjects were evaluated with a standard Japanese cognitive assessment of memory and general knowledge, which indicated that the largest proportion of subjects performed in the normal range at baseline (43%), but a significant proportion were demented (9%), and the remainder were either subnormal (30%) or predementia (17%). Results of repeated testing at 1-year follow-up indicated that greater walking was associated with a reduction in cognitive deficits (i.e., subjects categorized at a less impaired level at one-year testing). One strength of this study was its use of a community-based sample of older cardiac patients, although it was limited by the absence of a control group, minimal cognitive outcomes, and no objective measurement of fitness level.
Alzheimer's Disease
Only one published study has examined the impact of exercise on cognitive function among patients with Alzheimer's disease. Palleschi, Vetta, De Gennaro, and Idone (1996) evaluated the effects of a 3-month stationary-bicycle-riding intervention among 15 men (mean age 74 years) with dementia of the Alzheimer type. Cognitive assessment evaluated attention, verbal span, and the Mini-Mental State Exam. Results indicated improved performance on all cognitive tests. Although no control group was
P.134
included to account for practice effects, this study is an important first step in evaluating exercise effects among demented older adults. The paucity of research studies in this area may reflect, in part, the difficulty of conducting a systematic evaluation of patients with Alzheimer's disease. It also reflects the relative novelty of assessing exercise effects among patients with dementia, although exercise is often included in treatment programs for Alzheimer's patients in nursing-home or day-treatment settings.
Summary
Few studies have been conducted evaluating cognitive effects of exercise among chronically ill older adults. However, the limited data suggest that exercise may have beneficial effects for tasks reflecting attention, verbal capacity, and self-monitoring. Further, the data may indicate that subjects with cognitive impairment at baseline may be more likely to achieve cognitive gains with exercise. However, the data in this area are minimal, and only preliminary conclusions are possible at present.
Conclusions
Research studies of exercise among healthy older adults have become increasingly sophisticated in recent years. Studies now commonly utilize randomized control groups, including exercise controls as well as nonexercise controls, and objective indicators of cardiovascular fitness, such as VO2max. Studies have successfully recruited larger samples to increase the power of statistical analyses, and most studies of chronic exercise effects now routinely provide an exercise intervention of at least three 1-hour sessions per week over a 3- to 4-month period. Several studies have achieved more ambitious interventions of 12-month duration. However, there remains a lack of consistency in the data. While cross-sectional studies comparing long-term exercisers with sedentary older adults indicate an association of exercise with aspects of cognitive performance, these studies are severely limited by a self-selection bias. Intervention studies tend to suggest that exercise does not have a beneficial effect on cognitive functioning. One potential problem with past intervention studies documenting minimal improvements in neuropsychological functioning is that participation criteria for studies of healthy older adults may eliminate subjects exhibiting cognitive impairment, who could most benefit from exercise. Studies of impaired or chronically ill older adults are commonly conducted with small numbers of subjects, in part, because of the additional resources required to maintain adequate exercise adherence in these subjects. Although the small samples and unique characteristics of the subjects restrict generalizability, there is need for further study of exercise among chronically ill older adults (e.g., those with cardiovascular disease, pulmonary disease, dementing illnesses). Indeed, because changes in nondiseased older adults may, in fact, reflect early cognitive signs of occult disease, studies of older adults with chronic illness may have greater generalizability than it would appear.
One methodological limitation of data in this area is that the neuropsychological measures used to assess cognitive functioning may not be sensitive to the kinds of
P.135
changes occurring during exercise among older adults. Data indicate that older adults perceive significant improvements in cognitive function following regular exercise despite the absence of objective evidence of change (Emery & Blumenthal, 1990). Although self-reports of cognitive improvement may reflect a demand effect of exercise studies or a secondary result of enhanced mood following exercise, it is also possible that alternate measures of cognitive performance should be considered, assessing the types of everyday problem solving that older adults would be most likely to confront.
The research literature does not clearly support any single model to explain the association of cognitive functioning and exercise. The limited data from studies of acute exercise would support the notion that exercise increases mental arousal via enhanced central nervous system function or, perhaps, via reduction in sympathetic tone. Intervention studies, overall, do not provide support for cardiovascular fitness as a central factor in cognitive outcomes. Although the cross-sectional data provide support for the importance of cardiovascular fitness, these data are limited by self-selection factors. The data also do not support mood changes as a likely moderator of cognitive improvement in exercise intervention studies. Of the two studies in table 7.1 that demonstrated positive effects of aerobic exercise on cognitive function (Dustman et al., 1984; Williams & Lord, 1997), only the Williams and Lord study reported enhanced psychological well-being as well. Studies of acute exercise effects suggest positive effects on mood, although this may be true only for subgroups of subjects (Emery, Honn, Becker, & Frid, 1996). Any improvement in mood resulting from individual exercise sessions would be likely to contribute to exercise adherence and thus could be indirectly associated with enhanced cognitive performance. From this perspective, cognitive change in exercise programs may reflect several different processes associated with exercise. Further elaboration of acute exercise effects versus chronic effects may help to elucidate further the mechanisms by which exercise may affect cognitive functioning.
One practical goal for future research in this area would be to develop data-based guidelines for the use of exercise in prevention and rehabilitation of older adults with cognitive deficits or at risk for cognitive deficits. At present, there is no hard evidence to support the use of exercise for cognitive rehabilitation, and there are not clear guidelines for determining a correct dose of exercise. Thus, the research problem must be approached directly, and clinical applications must be instituted cautiously. Studies of physiological outcomes indicate guidelines for ensuring an exercise training effect (e.g., three times a week over a 3- to 4-month period). Presumably this would be a minimal criterion for interventions designed to increase cognitive performance, but positive results from the Dustman et al. (1984) study and Williams and Lord (1997) suggest that intensity level or duration may need to be considered further, since Dustman et al. observed a 27% increase in VO2max, and Williams and Lord evaluated a 42-week program of exercise. Thus, although cardiovascular improvements may occur within several months, cognitive changes may not occur without a very sizable increase in fitness or a long-term intervention. To the extent that the cross-sectional data indicate benefits of long-term exercise for cognitive performance, exercise may be important in preventing cognitive decline. From a prevention perspective, it may be more appropriate to hypothesize that exercise will prevent cognitive
P.136
decline rather than that exercise will augment cognitive functioning. Longitudinal studies would help address the utility of a prevention model in research on cognitive function.
Indeed, the data overall suggest a need for methodologically strong longitudinal studies evaluating exercise performance and cognitive functioning. Use of objective markers of cardiovascular fitness would be imperative, as well as providing a consistent exercise stimulus and accounting for important individual differences in health behavior, educational attainment, and cultural differences. Although most exercise interventions are conducted in a group format, several studies have evaluated home exercise programs in which the subject may exercise alone. Such interventions may have greater practical utility among older populations and may facilitate collecting longitudinal data. In addition to studies evaluating longitudinal effects of exercise interventions, there is a need for further research evaluating gender differences in cognitive outcomes of exercise.
References
Aniansson, A., Grimby, G., Rundgren, A., Svanborg, A., & Orlander, J. (1980). Physical training in old men. Age and Ageing, 9, 186 187.
Bachmann, G. A., & Grill, J. (1987). Exercise in the postmenopausal woman. Geriatrics, 42, 75 77, 81 85.
Barclay, L. L., Weiss, E. M., Mattis, S., Bond, O., & Blass, J. P. (1988). Unrecognized cognitive impairment in cardiac rehabilitation patients. Journal of the American Geriatrics Society, 36, 22 28.
Blumenthal, J. A., Emery, C. F., Madden, D. J., George, L. K., Coleman, R. E., Riddle, M. W., McKee, D. C., Reasoner, J., & Williams, R. S. (1989). Cardiovascular and behavioral effects of aerobic exercise training in healthy older men and women. Journal of Gerontology, 44, M147-157.
Blumenthal, J. A., Emery, C. F., Madden, D. J., Schniebolk, S., Walsh-Riddle, M., George, L. K., Higginbotham, M. B., McKee, D. C., Sullivan, M. J., & Coleman, R. E. (1991). Long term effects of exercise on psychological functioning in older men and women. Journal of Gerontology, 46, P352-361.
Bortz, W. (1982). Disease and aging. Journal of the American Medical Association, 248, 1203 1208.
Bouchard, C., Shephard, R. J., Stephens, T., Sutton, J. R., & McPherson, B. D. (1990). Exercise, fitness, and health: The consensus statement. In Bouchard, C., Shephard, R. J., Stephens, T., Sutton, J. R., & McPherson, B. D. (Eds.), Exercise, fitness, and health (pp. 3 28). Champaign, IL: Human Kinetics.
Bruce, R.A. (1984). Exercise, functional aerobic capacity, and aging-another viewpoint. Medicine and Science in Sports and Exercise, 16, 8 13.
Buskirk, E. R., & Hodgson, J. L. (1987). Age and aerobic power: The rate of change in men and women. Aging and Exercise: Physiological Interactions. Federation Proceedings, 46, 1824 1829.
Clarkson-Smith, L., & Hartley, A. A. (1989), Relationships between physical exercise and cognitive abilities in older adults. Psychology and Aging, 4(2), 183 189.
Craik, F. I. M., & Jennings, J. M. (1992). Human memory. In F. I. M. Craik & T. A. Salthouse (Eds.), Handbook of aging and cognition (pp. 51 110). Hillsdale, NJ: Erlbaum.
DiGiovanna, A.G. (1994). Human aging: Biological perspectives. New York: McGraw-Hill.
P.137
Dustman, R. E., Emmerson, R. Y., Ruhling, R. O., Shearer, D. E., Steinhaus, L. A., Johnson, S. C., Bonekat, H. W., & Shigeoka, J. W. (1990). Age and fitness effects on EEG, ERPs, visual sensitivity, and cognition. Neurobiology of Aging, 11, 193 200.
Dustman, R., Ruhling, R., Russell, E., Shearer, D., Bonekat, W., Shigeoka, J., Wood, J., & Bradford, D. (1984). Aerobic exercise training and improved neuropsychological function of older individuals. Neurobiology of Aging, 5, 35 42.
Ehsani, A. A. (1987). Cardiovascular adaptations to exercise training in the elderly. Aging and Exercise: Physiological Interactions. Federation Proceedings, 46, 1840 1843.
Eisdorfer, C., Nowlin, J., & Wilkie, F. (1970). Improvement of learning in the aged by modification of autonomic nervous system activity. Science, 170, 1327 1329.
Elsayed, M., Ismail, A., & Young, R. (1980). Intellectual differences of adult men related to age and physical fitness before and after an exercise program. Journal of Gerontology, 35, 383 387.
Emery, C. F., & Blumenthal, J. A. (1990). Perceived change among participants in an exercise program for older adults. Gerontologist, 30, 516 521.
Emery, C. F., & Gatz, M. (1990). Psychological and cognitive effects of an exercise program for community-residing older adults. Gerontologist, 30, 184 188.
Emery, C. F., Honn, V., Becker, N. L., & Frid, D. J. (1996). Acute effects of exercise on mood and cognitive function of older adults (abstract). Gerontologist, 36(1), 53.
Emery, C. F., Schein, R. L., Hauck, E. R., & MacIntyre, N. R. (1998). Psychological and cognitive outcomes of a randomized trial of exercise among patients with chronic obstructive pulmonary disease. Health Psychology, 17, 232 240.
Evans, W. J., & Cyr-Campbell, D. (1997). Nutrition, exercise, and healthy aging. Journal of the American Dietetic Association, 97, 632 638.
Fishman, D. B., & Petty, T. L. (1971). Physical, symptomatic and psychological improvement in patients receiving comprehensive care for chronic airway obstruction. Journal of Chronic Diseases, 24, 775 785.
Garcia, C. A., Tweedy, J. R., & Blass, J. P. (1984). Underdiagnosis of cognitive impairment in a rehabilitation setting. Journal of the American Geriatrics Society, 32, 339 342.
Grant, I., Heaton, R. K., McSweeny, A. J., Adams, K. M., & Timms, R. M. (1980). Brain dysfunction in COPD. Chest, 77(Suppl.), 308 309.
Grant, I., Heaton, R. K., McSweeny, A. J., Adams, K. M., & Timms, R. M. (1982). Neuropsychologic findings in hypoxemic chronic obstructive pulmonary disease. Archives of Internal Medicine, 142, 1470 1476.
Gutin, B. (1966). Effect of increase in physical fitness on mental ability following physical and mental stress. Research Quarterly, 37: 211 220.
Gutin, B., & DiGennaro, J. (1968). Effect of one-minute and five-minute step-ups on performance of simple addition. Research Quarterly, 39, 81 85.
Hassmen, P., Ceci, R., & Backman, L. (1992). Exercise for older women: A training method and its influences on physical and cognitive performance. European Journal of Applied Physiology & Occupational Physiology, 64(5), 460 466.
Heaton, R. K., Grant, I., McSweeny, A. J., Adams, K. M., & Petty, T. L. (1983). Psychologic effects of continuous and nocturnal oxygen therapy in hypoxemic chronic obstructive pulmonary disease. Archives of Internal Medicine, 143, 1941 1947.
Hill, R. D., Storandt, M., & Malley, M. (1993). The impact of long-term exercise training on psychological function in older adults. Journal of Gerontology: Psychological Sciences, 48(1), 12 17.
Horn, J., Donaldson, G., & Engstrom, R. (1981). Apprehension, memory, and fluid intelligence decline in adulthood. Research on Aging, 3, 33 44.
Jacobs, E. A., Winter, P. M., Alvis, H. J., & Small, S. M. (1969). Hyperoxygenation effect on cognitive functioning in the aged. New England Journal of Medicine, 281, 753 757.
P.138
Kasch, F. W., Wallace, J. P., & Van Camp, S. P. (1985). Effects of 18 years of endurance exercise on the physical work capacity of older men. Journal of Cardiopulmonary Rehabilitation, 5, 308 312.
Kennelly, K., Hayslip, B., & Richardson, S. (1985). Depression and helplessness-induced cognitive deficits in the aged. Experimental Aging Research, 11, 169 173.
Krop, H., Block, A. J., & Cohen, E. (1973). Neuropsychologic effects of continuous oxygen therapy in chronic obstructive pulmonary disease. Chest, 64, 317 322.
Lezak, M. D. (1995). Neuropsychological assessment (3rd ed.). New York: Oxford University Press.
Madden, D. J., Blumenthal, J. A., Allen, P. A., & Emery, C. F. (1989). Improving aerobic capacity in healthy older adults does not necessarily lead to improved cognitive performance. Psychology and Aging, 4, 307 320.
Mahler, D. A., Rosiello, R. A., & Loke, J. (1986). The aging lung. Geriatrics Clinics of North America, 2, 215 225.
McMurdo, M. E. T., & Rennie, L. M. (1994). Improvements in quadriceps strength with regular seated exercise in the institutionalized elderly. Archives of Physical Medicine and Rehabilitation, 75, 600 603.
Molloy, D., Beerschoten, D., Borrie, M., Crilly, R., & Cape, D. (1988). Acute effects of exercise on neuropsychological function in elderly subjects. Journal of the American Geriatrics Society, 36, 29 33.
Molloy, D. W., Richardson, L. D., & Crilly, R. G. (1988). The effects of a three-month exercise programme on neuropsychological function in elderly institutionalized women: A randomized controlled trial. Age and Ageing, 17, 303 310.
Nieman, D. C, Warren, B. J., O'Donnell, K. A., Dotson, R. G., Butterworth, D. E., & Henson, D. A. (1993). Physical activity and serum lipids and lipoproteins in elderly women. Journal of the American Geriatrics Society, 41, 1339 1344.
Okumiya, K., Matsubayashi, K., Wada, T., Kimura, S., Doi, Y., & Ozawa, T. (1996). Effects of exercise on neurobehavioral function in community-dwelling older people more than 75 years of age. Journal of American Geriatric Society, 44, 569 572.
Palleschi, L., Vetta, F., De Gennaro, E., & Idone, G. (1996). Effect of aerobic training on the cognitive performance of elderly patients with senile dementia of Alzheimer type. Archives of Gerontology and Geriatrics (Suppl. 5), 47 50.
Panton, L. B., Graves, J. E., Pollock, M. L., Hagberg, J. M., & Chen, W. (1990). Effect of aerobic and resistance training on fractionated reaction time and speed of movement. Journal of Gerontology, 45, M26 31.
Perri, S., & Templer, D. (1984 1985). The effects of an aerobic exercise program on psychological variables in older adults. International Journal of Aging and Human Development, 20, 167 172.
Powell, R. R. (1974). Psychological effects of exercise therapy upon institutionalized geriatric mental patients. Journal of Gerontology, 29, 157 161.
Prigatano, G. P., Parsons, O., Wright, E., Levin, D. C., & Hawryluk, G. (1983). Neuropsychological test performance in mildly hypoxemic patients with chronic obstructive pulmonary disease. Journal of Consulting and Clinical Psychology, 51, 108 116.
Prinz, P. N., Dustman, R. E., & Emmerson, R. Y. (1990). Electrophysiology and aging. In J. E. Birren & K. W. Schaie (Eds.), Handbook of the psychology of aging (3rd ed.). San Diego: Academic Press.
Pyka, G., Lindenberger, E., Charette, S., & Marcus, R. (1994). Muscle strength and fiber adaptations to a year-long resistance training program in elderly men and women. Journal of Gerontology, 49, 22 27.
Raz, I., Hauser, E., & Bursztyn, M. (1994). Moderate exercise improves glucose metabolism in uncontrolled elderly patients with non-insulin-dependent diabetes mellitus. Israel Journal of Medical Sciences, 30, 766 770.
P.139
Rikli, R., & Busch, S. (1986). Motor performance of women as a function of age and physical activity level. Journal of Gerontology, 41(5), 645 649.
Robinson, M., Blumenthal, J. A., Burker, E. J., Hlatky, M., & Reves, J. G. (1990). Coronary artery bypass grafting and cognitive function: A review. Journal of Cardiopulmonary Rehabilitation, 10, 180 189.
Rudman, D., Kutner, M. H., Rogers, C. M., Lubin, M. F., Fleming, G. A., & Bain, R. P. (1981). Impaired growth hormone secretion in the adult population relation to age and adiposity. Journal of Clinical Investigation, 67, 1361 1369.
Salthouse, T. A. (1991). Theoretical perspectives on cognitive aging. Hillsdale, NJ: Erlbaum.
Satoh, T., Sakurai, I., Miyagi, K., & Hohshaku, Y. (1995). Walking exercise and improved neuropsychological functioning in elderly patients with cardiac disease. Journal of Internal Medicine, 238, 423 428.
Shay, K. A., & Roth, D. L. (1992). Association between aerobic fitness and visuospatial performance in healthy older adults. Psychology and Aging, 7, 15 24.
Singh, N. A., Clements, K. M., & Fiatarone, M. A. (1997). A randomized controlled trial of the effect of exercise on sleep. Sleep, 20, 95 101.
Spirduso, W. W. (1975). Reaction and movement time as a function of age and physical activity level. Journal of Gerontology, 30, 435 440.
Spirduso, W. W. (1980). Physical fitness, aging, and psychomotor speed: A review. Journal of Gerontology, 35, 850 865.
Stacey, C., Kozma, A., & Stones, M. J. (1985). Simple cognitive and behavioural changes resulting from improved physical fitness in persons over 50 years of age. Canadian Journal on Aging, 4, 67 74.
Stevenson, J. S., & Topp, R. (1990). Effects of moderate and low intensity long-term exercise by older adults. Research in Nursing & Health, 13(4), 209 218.
Stones, M. J., & Kozma, A. (1989). Age, exercise, and coding performance. Psychology and Aging, 4, 190 194.
Strandell, T. (1976). Circulatory studies on healthy old men. Acta Medica Scandinavica, 414, 1 43.
Tamai, T., Nakai, T., Takai, H., Fujiwara, R., Miyabo, S., Higuchi, M., & Kobayashi, S. (1988). The effects of physical exercise on plasma lipoprotein and apolipoprotein metabolism in elderly men. Journal of Gerontology, 43, M75-79.
Tate, C. A., Hyek, M. F., & Taffet, G. E. (1994). Mechanisms for the responses of cardiac muscle to physical activity in old age. Medicine and Science in Sports and Exercise, 26, 561 567.
Tomporowski, P. D., & Ellis, N. R. (1986). Effects of exercise on cognitive processes: A review. Psychological Bulletin, 99, 338 346.
Williams, P., & Lord, S. R. (1997). Effects of group exercise on cognitive functioning and mood in older women. Australian and New Zealand Journal of Public Health, 21(1), 45 52.
EAN: 2147483647
Pages: 18