Invited minireviewCardiovascular fitness and neurocognitive function in older Adults: a brief review
Introduction
There are currently 35 million adults aged 65 years and older in the US, a figure that is expected to double over the next several decades. Adults aged 85 years and older are the fastest growing segment of our population and this group is expected to grow from 4 million in 2000 to 19 million by 2050. Although mortality rates are decreasing and life expectancy is increasing (Federal Interagency Forum on Aging-Related Statistics, 2000), it is not well-established whether older adults are experiencing a better quality of life as they age. Indeed, quality of life can be considered a more important goal of health promotion than longevity. Quality of life is viewed by many as having multiple functional and well-being components (Stewart and King, 1991). One aspect of function that has been well-established as demonstrating age-related declines is cognitive function, typically characterized by decrements in a variety of processes including aspects of memory, attention, and perception. Declines in cognition have been identified as a major risk factor for nursing home entry (Federal Interagency Forum on Aging-Related Statistics, 2000) and age-associated diseases such as Alzheimer’s Dementia (Wilson et al., 2002). Consequently, development of strategies to maintain or enhance cognitive function in later life is an important public health goal.
One behavioral modality that has been implicated in maintaining and enhancing multiple aspects of physical and psychological functioning across the lifespan is physical activity. As a modifiable risk factor, physical inactivity has been implicated in a variety of health conditions including cardiovascular disease, adult onset diabetes, cancer, disability, depression, and cognitive decline (Bouchard et al., 1994). In this paper, we examine the utility of physical activity and more specifically cardiovascular fitness training as a behavioral strategy for improving cognitive function in older adults through its effects on cardiovascular fitness (see Fig. 1). Reviewing the literature from both animal and human studies, we consider the extent to which fitness training might be an effective strategy for the maintenance of cognitive function and brain plasticity in late life. However, any such effects are predicated on keeping participants active over considerable periods of time. Unfortunately, sedentary behavior among older adults is highly prevalent. Even when older adults take up physical activity in community settings, the adherence rates have been reported to be little better than those reported for other segments of the population (Rhodes et al., 1999). Consequently, we discuss issues relative to adherence, in particular the social cognitive determinants of exercise behavior. Finally, we conclude with a brief section identifying areas of future endeavor in cardiovascular fitness and neurocognitive function.
Section snippets
Fitness training and cognition
Early studies of the relationship between fitness and cognition, which date back at least four decades, compared the cognitive performance of low and high fit older adults on an array of paper and pencil and computer-based tasks. In general, these studies found that higher fit individuals were able to perform more quickly and accurately on a wide variety of perceptual, cognitive, and motor tasks than low fit individuals (see Etnier et al., 1997, for review). However, whereas these early results
Animal research on fitness, brain structure, brain function, and performance
The animal research on fitness effects on brain function and structure can be traced to a long-term interest of neuroscientists in brain plasticity. Much of the early research on brain plasticity examined the influence of enriched versus impoverished environments with rats and mice but was restricted to the study of young animals, largely because brain plasticity was believed to exist only in young organisms. However, later research discovered that morphological changes in brain structure could
Beyond cognition and fitness: human studies of the relationship between fitness and brain structure and function
The studies reviewed above suggest that fitness effects can be observed in both brain structure and function. However, thus far the study of fitness effects on cognitive function and brain structure has been largely confined to humans and animals, respectively. A recent study from our research group (Colcombe et al., 2003) attempted to bridge this gap by examining the relationship between the density of cortical grey and white matter and aerobic fitness in a sample of adults ranging from 55 to
Behavioral issues relevant to fitness effects on brain structure and function
Employing cardiovascular fitness training as a behavioral intervention to maintain and enhance brain structure and function is an exciting avenue of research with the potential for a considerable public health yield. However, it is important to remember that such effects are a function of a behavioral intervention and therefore all benefits are predicated on successfully adhering to exercise regimens. Unfortunately, sedentary behavior among adults represents more normative behavior than an
Future research directions
The research that we have reviewed above has suggested that cardiovascular fitness training can have a variety of beneficial effects on cognition, brain, and psychosocial function of older adults. However, the literature also points to a number of gaps in our knowledge. For example, the Colcombe and Kramer (2002) meta-analysis suggests that women benefit more than men with respect to the cognitive benefits of fitness training and that combined aerobic and strength training interventions have a
Acknowledgments
The preparation of this report and the research that we described from our laboratories was supported by the Institute for the Study of Aging and the National Institute on Aging (AG18008; AG 12113). Authorship of this manuscript is considered joint and reprints can be requested from any of the authors at: [email protected]; [email protected]; [email protected].
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