The concept of successful aging typically incorporates a person’s feelings of well-being, optimism, and ability to cope with the vicissitudes of the midlife years and beyond. Yet, keeping mentally sharp is important to many people as they grow older. Successful cognitive aging depends in large part on successful brain aging. Though we often think bigger is better when it comes to the brain, as it turns out, the way the brain functions may be more important than its actual size. As we say about certain other bodily areas, then, size doesn’t always matter; it’s how you use what you’ve got.
To understand successful brain aging, it is helpful to look first at what we mean by "optimal" aging. Unlike what we associate with losses that accumulate over time (“normal” or “usual” aging), optimal aging improves the individual’s functioning. Now think about people you would nominate as successful, or optimal, agers. What characterizes them? Are they physically stronger than their age peers? Do see better or hear better than people in their 20s and 30s? How about some of those older adults who have become cultural icons, such as Betty White or Jack LaLanne? In an earlier blog, I wrote about these and other amazing older adults, who I call the “Age Busters,” because they “bust” the stereotypes that aging inevitably involves infirmity and obsolescence. You probably know plenty of age busters in your family, neighborhood, or community; maybe you’re one yourself!
These examples show that it is possible for both ordinary and famous older adults to defy traditional stereotypes about aging. How do these optimal agers pull it off? Clearly, there is some set of qualities that allow them to maintain their zest and vitality well into their 60s, 70s, and beyond. To answer this question, we turn to what gerontologists Rowe and Kahn (1998), defined as “successful aging:” (1) absence of disease, (2) absence of disability, (3) high cognitive and physical functioning, (4) and engagement with life. However, based on numerous investigations, including the University of Michigan’s Institute of Social Research Health and Retirement Study (HRS) on approximately 10,000 U.S. adults (McLaughlin et al., 2010), Rowe and Kahn’s definition is overly restrictive. Using all 4 criteria limits the estimate of successful agers to about 10%. The problem was in the restrictiveness of having “no disease.” Approximately 80% of the HRS elders rated themselves as disability-free, but only about 40% stated that they had no health problems. The Rowe and Kahn definition also fails to take into account social class, race and ethnicity, as shown by studies on other samples (e.g. urban African American older adults in a study by Cernin et al., 2011). In the HRS, successful agers were more heavily represented among Whites and among those with a college education or higher.
The World Health Organization (WHO) definition takes a more liberal approach, and recognizes that people who are objectively not free from health conditions can still have a high quality of life. The WHO defines “active ageing” as the process of optimizing opportunities for health, participation and security in order to enhance quality of life as people age. WHO makes explicit the role of autonomy and independence, placing greater emphasis on the individual’s ability to get around in the environment, rather than on whether or not the individual needs physical accommodations due to disability.
Seeking to quantify successful aging further, and with these considerations in mind, University of California at San Diego researchers led by Ipsit Vahia (2012) administered several standardized measures to nearly 1,950 women participating in the San Diego site of the Women’s Health Initiative (WHI) Study in an attempt to predict self-rated successful aging. They found that the women highest in subjectively-rated successful aging had high scores in what they called the psychological protective factors of resilience, self-efficacy, and optimism, they had positive emotional functioning (low depression and emotional symptoms), and were low in self-rated disability.
Being emotionally resilient can give you an edge in aging successfully. However, cognitive abilities are also key to the overall ability to become an Age Buster. Being able to use your brain may not guarantee you emotional happiness or even material success, but having greater brain reserves can help you adapt to the challenges of daily life. Older adults regard their cognitive abilities as central to their sense of identity, which is one reason that they so greatly fear developing Alzheimer’s disease.
Researchers are now setting on the path to discover the elements of what they call “successful cognitive aging,” or cognitive performance that is above the average for an individual’s age group as objectively measured (Fiocco & Yaffe, 2010). Instead of seeking only to define and diagnose neurocognitive disorders, the pioneering researchers in this field are following up on the concept of “plasticity,” identified by neuroanatomists Coleman and Flood (1987) after their discoveries that in the normal brain, neurons continue to develop the ability to form new branches even as the total numbers of neurons may diminish with age.
Successful cognitive aging clearly requires successful brain aging. To prove this point, Northwestern University’s Theresa Harrison and colleagues (2012) identified a subset of participants in one of their studies who met the criteria for memory “SuperAgers” in that they performed at levels comparable to those of middle-aged adults. When Harrison and her team looked at the brain scans of the SuperAgers, they found that they were equivalent in terms of cortical thickness in key areas to those of the middle-aged participants, and better than those of the age-matched non-SuperAger peers. If you want to be a memory Age Buster, it looks like you have to be a brain Age Buster as well.
Over the past 25 years or so, neuroscientists have been quietly amassing a set of studies in which the brain scans of older adults are compared to those of younger adults, cataloging the relationships of brain scans to cognitive performance. Although the Harrison et al. study is notable in showing a direct correspondence between cortical thickness and memory performance, others have brought some pretty good correlational evidence to bear on the question. UC San Diego researcher Jeste teamed up with a group led by Lisa Eyler in 2011 to review 80 of the best of these studies to find out whether people with better brain response (not just size) would also have better cognitive performance. In other words, does successful brain aging translate into successful cognitive aging?
Of the 80 studies, 39% showed a clear connection among the older adults between brain activation and cognitive performance and another 32% showed mixed findings. The remainder showed either no relationship or a negative relationship. Breaking the findings down by brain region, the best findings appeared for the frontal cortex, tapped by so-called “executive” functions important for planning and decision-making, and thought to be targeted particularly negatively by aging. Another area called the medial temporal lobe, which contains the all-important-for-memory structure known as the hippocampus, tended to show positive relationships to performance, but not consistently. Eyler and her team, from this evidence, concluded that “a simple model of bigger structure -->greater brain response -->better cognitive performance might not be accurate for this region” (p. 118).
If size doesn’t count, what does? Successful cognitive aging means that you make the best use of your brain, however large or small it might be. As we know from scaffolding theory, people can build upon their existing brain structures to put them to optimal use. If one brain region is lagging behind, another can make up for it. This concept takes plasticity to new levels because it’s not just that you build more onto your existing neurons, but that you switch out one brain region to compensate for losses in another. In one form of brain switching, called Hemispheric Asymmetry Reduction in OLDer adults (HAROLD) (Cabeza, 2002), a region in one hemisphere takes up the job usually carried out by the corresponding region in the other. The second form of brain switching is called the Posterior–Anterior Shift with Aging (PASA) (Davis et al., 2008), in which the frontal lobes takes up the extra work when the posterior lobes are not able to carry on their tasks.
The key to successful cognitive aging is having a better brain, but not necessarily a bigger brain. The most successful brain agers are the ones who can reorganize their brain regions so that the strong areas take over for the weak.
How can you become a cognitive SuperAger? Take advantage of the principles of plasticity. We have ample evidence showing that physical and mental exercise can help you maintain and improve a variety of cognitive abilities from memory to higher-order decision making and planning (those frontal area functions). Not only can you benefit directly from these stimulating activities, but your mood will improve, and you’ll feel mentally and physically sharper. From there, it’s a relatively straight path to overall successful aging, where your spirit and vitality for life will continue to grow.
Exercising your brain shouldn’t have the same goals as exercising your body’s muscles. Bigger is not always better in the brain, it’s all about how you use what you have.
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Copyright Susan Krauss Whitbourne, Ph.D. 2013
Cabeza, R. (2002). Hemispheric asymmetry reduction in older adults: The HAROLD model. Psychology and Aging, 17(1), 85-100.
Cernin, P. A., Lysack, C., & Lichtenberg, P. A. (2011). A comparison of self-rated and objectively measured successful aging constructs in an urban sample of African American older adults. Clinical Gerontologist: The Journal of Aging and Mental Health, 34(2), 89-102.
Coleman, P. D., & Flood, D. G. (1987). Neuron numbers and dendritic extent in normal aging and Alzheimer's disease. Neurobiology of Aging, 8(6), 521-545.
Davis, S. W., Dennis, N. A., Daselaar, S. M., Fleck, M. S., & Cabeza, R. (2008). Qué PASA? The posterior-anterior shift in aging. Cerebral Cortex, 18(5), 1201-1209.
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