Dr. Vance is Associate Professor, Dr. Roberson is Assistant Professor, Dr. McGuinness is Professor, School of Nursing, and Ms. Fazeli is a graduate student, Department of Psychology and Center for Research in Applied Gerontology, University of Alabama at Birmingham, Birmingham, Alabama.
The authors disclose that they have no significant financial interests in any product or class of products discussed directly or indirectly in this activity, including research support.
Address correspondence to David E. Vance, PhD, MGS, Associate Professor, School of Nursing, University of Alabama at Birmingham, 1701 University Boulevard, Room 456, Birmingham, AL 35294-1210; e-mail: email@example.com.
Cognitive functioning is essential for negotiating one’s environment, engaging in one’s vocation, enjoying social and personal experiences, and of course, consciousness itself. Yet, because of the automatic nature and fluidity of cognitive functioning, frequently it is ignored in routine health care until obvious problems occur. Only with advancing age do health care professionals begin to routinely inquire about the cognitive functioning of patients. This article provides a model, based on the evidence in the literature, to support approaches for engaging patients in behaviors to promote and protect cognitive health across the life span.
Age-related cognitive declines in memory, attention, speed of processing, executive functioning, and psychomotor ability are well-documented phenomena (Ball, Vance, Edwards, & Wadley, 2004). In a sample of community-dwelling adults in their 70s, Low et al. (2004) found a third of the sample exhibited significant cognitive impairment without dementia. McGuire, Ford, and Ajani (2006) observed that even moderate declines in cognitive functioning, without dementia, can interfere with everyday tasks such as managing finances, shopping for groceries, and adhering to medication regimens.
Although several methods for improving cognitive functioning or mitigating cognitive loss in older adults exist (Ball et al., 2004), the ideal time to intervene is throughout the entire life span before functional problems emerge. This article presents the principles of cognitive reserve and neuroplasticity and reviews the factors associated with these principles. A multifactorial model of cognitive functioning is posited along with a scenario of how this works, and implications for nursing practice and research are discussed.
Neuroplasticity and Cognitive Reserve
Neuroplasticity and cognitive reserve are two interrelated concepts that elucidate how cognitive functioning atrophies or is maintained and ameliorated. Neuroplasticity is the process by which the brain and nervous system produce morphological changes in response to environmental stimuli; these changes may be positive or negative.
Positive neuroplasticity refers to morphological changes in the brain that occur as one experiences novel and challenging environmental stimuli. Such changes can include an increase in dendritic connections between neurons, an increase in brain size, stronger connections between neurons, and an increase in neutrophic factors, all of which promote cognitive functioning (Vance & Crowe, 2006).
In contrast, negative neuroplasticity refers to morphological changes in the brain that occur as one experiences a lack of novel, challenging environmental stimuli and diminished health. Such changes can include a decrease in dendritic connections between neurons, a decrease in brain size, weaker connections between neurons, and a decrease in neutrophic factors, all of which promote poor cognitive functioning (Vance & Crowe, 2006). These structural changes have an impact on cognitive reserve.
Cognitive reserve refers to those structural changes that support cognitive functioning. Thus, as those structural changes support and improve cognitive functioning, the greater one’s cognitive reserve, and the more resistant one will be to neurological insults (e.g., substance abuse, transient ischemic attacks) that negatively affect cognitive functioning. In fact, lifelong changes in positive and negative neuroplasticity and the physiological factors that influence neuroplasticity (e.g., cardiovascular fitness via physical activity) determine how much cognitive reserve and cognitive functioning one possesses in later life. These processes have been well observed in animals.
Numerous animal studies have used the enriched environmental paradigm to demonstrate that rats of all ages can benefit from exposure to an enriched environmental condition compared with rats placed in a standard or impoverished environmental condition. For example, Kobayashi, Ohashi, and Ando (2002) randomized adult rats to either an enriched or a standard environmental condition. Rats in the enriched environmental condition were placed in a large cage with 11 other rats and a variety of toys to explore. These toys were exchanged weekly with new toys. Rats in the standard condition were placed in a smaller cage with 2 other rats; no toys were present.
On the basis of the principles of neuroplasticity and cognitive reserve, rats placed in the enriched environmental condition were hypothesized to experience more positive structural changes in their brains, resulting in better cognitive functioning compared with those rats placed in the standard environmental condition. Consistently, this is what has been reported in the literature.
In the study by Kobayashi et al. (2002), rats in the enriched environmental condition completed the Hebb-Williams maze task significantly faster than rats assigned to the standard environmental condition. This finding demonstrates that exposure to an enriched environment—in this case more social contact with other rats and novel stimuli from toys—encourages positive neuroplasticity and increases cognitive reserve, which translates into better cognitive functioning. Such enrichment of environments has parallels to the human world as well.
Positive Neuroplasticity and Good Neurological Health
As shown in Figure 1, several factors promote positive neuroplasticity and improve cognitive reserve and cognitive functioning through facilitating neuroplasticity or enhancing lifestyle behaviors that support the physiological function of neuroplasticity. Some of these factors, which can work separately or in tandem, are:
- Physical activity.
- Social interactions.
- Intellectual pursuits.
- Cognitive remediation.
Figure 1: Factors that Affect Neuroplasticity and Cognitive Reserve Across the Life Span.
Numerous studies have demonstrated the positive effects physical activity has on brain health and cognition. Compared with baseline stress when participants were not engaged in exercise, Kamijo et al. (2009) demonstrated in 12 young men (mean age = 21.8) and 12 older men (mean age = 65.5) that engaging in light to moderate aerobic exercise (e.g., cycling) can increase reaction time and result in improved event-related potentials in the brain. The findings of this study and similar studies (e.g., Colcombe et al., 2006; Hillman, Kramer, Belopolsky, & Smith, 2006) suggest that light to moderate aerobic exercise can improve cognitive functioning across the life span.
Education appears to be the human equivalent of the previously described enriched environmental paradigm among rats. In fact, education alone appears to be one of the single most important factors involved in positive neuroplasticity and cognitive reserve. Several studies show that obtaining higher levels of education appears to be protective against age-related cognitive loss and may even delay the onset of dementia (e.g., Whalley, Deary, Appleton, & Starr, 2004).
Such findings make sense when one considers the enormous amount of mental exercise exerted in the pursuit of higher education. Vast amounts of new information must be memorized, stored, retrieved, and manipulated during the course of several or many years for mastery to be achieved. In doing so, positive neuroplasticity occurs, resulting in new areas of the brain being used, which in turn produces an enriched and increased cognitive reserve.
The enriched environmental paradigm provides a framework to examine the importance of social interaction on neuroplasticity and cognitive reserve. Lu et al. (2003) assigned 22-day old rats to live either in isolation or with other rats for 4 to 8 weeks. Researchers discovered that rats housed with other rats exhibited more neurogenesis in the hippocampus, the region responsible for memory consolidation.
These findings are also analogous to human experiences. Emerging evidence suggests that adults who are socially integrated experience a reduced risk of developing dementia or have later onset dementia (Fratiglioni, Paillard-Borg, & Winblad, 2004). Many neuroscientists argue that the complexities of human social interactions are so dynamic and stimulating, they offer a host of challenging situations that force the brain to adapt, resulting in positive neuroplasticity and increased cognitive reserve (Vance & Crowe, 2006).
Several studies have demonstrated the efficacy intellectual pursuits have in fostering neuroplasticity and cognitive reserve, which can be protective against cognitive decline in later life. In their study, Grant and Brody (2004) showed that compared with adults without musical experience, older adults who were former or current orchestral members were significantly less likely to develop dementia or had a later onset of dementia, emphasizing the benefits of experience-dependent learning.
In a recent seminal study, Boyke, Driemeyer, Gaser, Buchel, and May (2008) taught 25 older adults (mean age = 60) to juggle. Magnetic resonance images (MRIs) were obtained before these participants learned to juggle, 3 months immediately after learning to juggle, and then 3 months later when juggling training ended. Analysis of the MRIs revealed that compared with baseline data, there was significant growth in the gray matter of the nucleus accumbens and hippocampus; however, this brain growth was not observed in the final MRI when participants no longer practiced and lost the ability to juggle.
Cognitive remediation therapy represents a relatively new way of improving cognitive reserve in adults. Typically, such cognitive remediation therapy is administered in a computer format whereby mental exercises of increasing complexity and difficulty are administered to participants to promote cognitive gains in particular domains such as speed of processing or reasoning.
In the largest clinical trial investigating cognitive remediation therapy (Ball et al., 2002), 2,832 community-dwelling older adults (age 65 and older) were randomly assigned to a speed of processing training condition (n = 712), a memory training condition (n = 711), a reasoning training condition (n = 705), and a no-contact control condition (n = 704). In each of the training conditions, participants received 10 hours of training.
In the speed of processing group, participants were exposed to a computer program that presented target items in the middle of the screen between 17 and 500 milliseconds. Participants were instructed to recognize the object that was just presented as well as the position of an outside object on the screen. Feedback was provided as the presentation speed and task complexity were increased gradually. In the memory group, participants learned how to use and apply mnemonic techniques for remembering details from narratives and learning lists of words, as well as applying the techniques to everyday situations. In the reasoning group, participants practiced exercises designed to improve their problem solving skills by learning how to recognize logical and sequential patterns in number and letter series as well as real-life situations (e.g., medication schedules).
For these participants, reliable training gains were observed in the respective areas in which training occurred. In the speed of processing group, 87% of participants exhibited a reliable improvement on a measure of speed of processing, whereas those in the memory and reasoning groups exhibited a 26% and 74% reliable improvement on a measure of memory and reasoning, respectively (Ball et al., 2002).
Negative Neuroplasticity and Poor Neurological Health
As shown in Figure 1, several factors promote negative neuroplasticity and diminish cognitive reserve and cognitive functioning. Some of these factors, which can work separately or in tandem, are:
- Poor health.
- Poor sleep hygiene.
- Poor nutrition.
- Substance abuse.
- Depression and anxiety.
Obviously, poor health promotes negative neuroplasticity. Pulmonary disease, hypertension, and diabetes are associated with subtle cognitive declines and increased risk for dementia (Ball et al., 2004; Vance & Crowe, 2006). Likewise, polypharmacy increases with age and is known to impair cognitive functioning, even though some of these medications may ameliorate some of the negative cognitive effects produced by comorbidities. Clearly, improving one’s physical health will improve neurological functioning and subsequent cognitive ability.
Poor Sleep Hygiene
Poor sleep hygiene has been shown to contribute to poor memory consolidation and cognition. Tworoger, Lee, Schernhammer, and Grodstein (2006) found difficulty falling and staying asleep and short sleep duration (<5 hours per night) were associated with poor cognitive functioning 2 years later.
Studies also have found the type of sleep disruption may negatively affect different cognitive functions. Stickgold (2005) described several studies in which he and his colleagues administered three cognitive tests (motor adaptation, motor sequence, and visual texture discrimination tests) to participants and examined the association of their scores on different types of sleep.
The researchers reported several findings. First, participants performed better on the cognitive tests after 1 night of sleep; however, when participants were kept awake for an equivalent amount of time they were asleep, such improvements were not observed. Second, amount of slow-wave sleep (SWS) was significantly correlated with improvements in the motor adaptation test, whereas the amount of non-rapid eye movement (non-REM) sleep was significantly correlated with improvements in the motor sequence test. Third, the amount of REM and SWS was significantly correlated with improvements in the visual texture discrimination test. These studies demonstrate that not only is sleep important for improving cognitive functioning but also that good sleep architecture is important for maintaining cognitive functioning.
Good nutrition supports physiological and neurological health to promote positive neuroplasticity; conversely, poor nutrition exerts the opposite effect. Numerous studies have documented that malnutrition in older adults is associated with poor cognitive functioning. For example, in a review of the literature, Solfrizzi, Panza, and Capurso (2003) found vitamin deficiencies, especially B6, B12, and folates, as well as antioxidant deficiencies, such as vitamins E and C, were associated with increased risk of cognitive decline.
Alcohol and drug abuse negatively affect the physiology needed for positive neuroplasticity. Although moderate alcohol use, especially red wine, has been associated with being protective against cognitive decline in later life, probably through its stress and lipid lowering properties (Panza et al., 2004), heavy alcohol use and substance abuse have been shown to result in poor cognitive functioning in adolescence as well as increased risk of dementia in later life (Medina, Schweinsburg, Cohen-Zion, Nagel, & Tapert, 2007).
Depression and Anxiety
Negative mood has been shown to detrimentally affect cognitive functioning. In a sample of 641 older adults (ages 70 to 85), Comijs, Jonker, Beekman, and Deeg (2001) found the amount of depressive symptoms was associated with declines in speed of processing 3 years later. Similar effects have also been found for other negative affective states such as anxiety (Bierman, Comijs, Rijmen, Jonker, & Beekman, 2008). As adults cope with depression and anxiety, these mood problems can compromise neuroplastic abilities through increased cortisol levels and reduced brain metabolites (e.g., cholinecontaining compounds, glutamine) necessary for proper functioning (Ball et al., 2004), thus negatively affecting cognition.
These factors that support positive and negative neuroplasticity affect one’s overall cognitive reserve and cognitive ability throughout the life span and are particularly important in determining the amount of cognitive reserve one possesses in older age. Figure 2 provides a simplistic scenario of how this works. The dark semihorizontal line represents an individual’s overall cognitive status, which is dynamic across the life span. This status can be affected by a number of factors.
Figure 2: Scenario of Cognitive Changes Throughout the Life Span.
In this scenario, the individual may have experienced gains in overall cognitive status by pursuing advanced education in nursing or physics. Followed by this, the individual may have a number of intellectual pursuits that help maintain cognitive gains established during his or her educational years.
However, during early middle age, the individual may have developed a substance abuse problem, which may have caused a decrease in his or her cognitive status. After years of recovery, the individual may have found the tenacity to begin taking care of his or her health by engaging in strenuous physical activity known to support neurological health, and this compensation results in improved cognitive status.
In older age, this individual may experience a number of age-related losses such as declining health, loss of friends and family, and loneliness, all of which can contribute to depression and a decrease in cognitive functioning. On recognizing such cognitive decline, the individual’s nurse may suggest cognitive remediation as a way to improve cognitive functioning.
In this scenario, simple causative events are indicative of the individual’s overall cognitive status. In actuality, myriad positive and negative factors interact simultaneously to create a dynamic flow of cognitive functioning. For instance, some individuals may abuse substances but their involvement and intellectual pursuits may shield them from some of the detrimental effects of this negative factor. Thus, it is important to remember these factors, both positive and negative, interact simultaneously to affect cognitive functioning.
Implications for Nursing Practice and Research
Aging begins at birth, not at 50, 65, or 70. Choices individuals make today influence how successfully they will age. Rowe and Kahn (1997) proposed that successful aging requires three essential components:
- Avoiding disease and disability.
- Active engagement in life.
- Maximization of cognitive and physical functioning.
Cognitive functioning is one of those components needed to avoid disease and disability as well as actively engage in life. This assertion parallels the Healthy Brain Initiative proposed by the Centers for Disease Control and Prevention and the Alzheimer’s Association (2007), which aims “to maintain or improve the cognitive performance of all adults” (p. 1). This initiative proposed 44 actions to prevent and improve cognitive health in adults individually and the community, many of which include the factors proposed in Figure 1. The initiative also asserts cognitive health should be considered across the life span, not just during more advanced aging.
The factors that support or detrimentally affect positive neuroplasticity can be targeted for intervention. Such factors can be combined to accentuate improvement in cognitive functioning. For example, in a study currently being conducted by Ball et al. (National Institutes of Health/National Institute on Aging grant 5R01AG005739-23; see http://projectreporter.nih.gov/project_info_description.cfm?aid=7671227&icde=2425709 for details) titled “Improvement of Visual Processing in Older Adults,” physical activity was combined with a type of cognitive remediation therapy to improve visual speed of processing. Community-dwelling older adults were randomly assigned to one of four training conditions: physical activity plus speed of processing training, physical activity only, speed of processing training only, and mental stimulation only. The physical activity plus speed of processing training group received ten 1-hour aerobic exercise sessions along with ten 1-hour computerized speed of processing training sessions, the physical activity only group received ten 1-hour aerobic exercise sessions, and the speed of processing group received ten 1-hour computerized speed of processing training sessions. The mental stimulation group served as the control condition; this group received a workbook containing Sudoku tasks, crossword puzzles, and word jumbles.
Although this study is still under way, the researchers hypothesized that those who received the physical activity plus speed of processing training would experience the most significant cognitive gains compared with those in the other three conditions. This direction in research suggests the value in using these factors of neuroplasticity to facilitate successful cognitive aging. To help maintain or improve cognitive functioning in individuals, nurse researchers can arrange these factors to create synergistic interventions to examine their effect.
As health educators, nurses can inform patients about health practices that will facilitate successful cognitive aging in their patients, even if their patients are young. Studies suggest early life factors are particularly important to facilitate neuroplasticity in later life (Akers et al., 2006).
Using Figure 1 as both a guide and a didactic tool, nurse educators can work with their patients to develop a cognitive prescription designed to serve as a rubric to enhance patients’ cognitive functioning. This cognitive prescription can be individualized. For example, when discussing physical activity as a factor for increasing cognitive reserve, patients may express a love for hiking. Thus, hiking could be added to the cognitive prescription with instructions to “Go hiking twice per week for at least 30 minutes each time,” which indicates a dosage for the cognitive prescription. Making the prescription specific provides a structure that will encourage adherence.
Cognitive functioning is vital not only for engaging in everyday life but also for maintaining one’s health and well-being. Nurses are in a key position to help inform patients that their cognitive ability is dynamic throughout the life span and that it can be improved or decreased in response to health and lifestyle factors.
Given what is known about neuroplasticity and cognitive reserve, behaviors that are performed today will influence cognitive ability in later life as well. Unfortunately, many people do not consider cognitive exercise and other helpful behaviors until cognitive abilities begin to decline. In that vein, psychiatric and mental health nurses in particular may consider writing cognitive prescriptions for their patients, providing patients the tools and information needed to avoid cognitive decline and maintain optimal cognitive functioning in the present, which will benefit them in the future.
Such cognitive prescriptions may be a unique way in which patients understand that cognitive functioning must be maintained and checked just as much as physical functioning. This approach will become especially useful as the number of older adults increases.
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