The primary goal of the McDonnell Academy’s 6th International Symposium in Brisbane, Australia in September 2016 was to foster research collaborations among Academy partner institutions on major challenges facing societies around the world, especially energy and environment, food and water, public health, and population aging. As continuum to the Symposium, the Forum for Greater China (January 21, 2017 in Shanghai) will focus on one of these — Population Aging. As background, two McDonnell Academy Scholars in the PhD program in Psychology, Eylul Tekin and Oyku Uner, have prepared the following white paper on successful cognitive aging.
Breaking Misconceptions: Successful Cognitive Aging
As we age, we undergo many biological and behavioral changes. Most of these changes result in impaired cognitive performance, shown by numerous studies comparing older and younger adults on how they perform on a variety of cognitive tasks. They show that while we accumulate knowledge as we age, we become slower at processing information; we gradually have poor inhibitory control; and we have difficulties in remembering past episodes and planned actions. In effect, our ability to effectively and efficiently utilize the knowledge we accumulate declines over time. These age-related changes are referred to as cognitive aging or a cognitive decline, and are associated with negative stereotypes of aging.
Although aging is inevitable, recent work has begun to shed light on ways to safeguard against negative components of cognitive aging.
Being in intellectually challenging environments and being physically active are associated with successful cognitive aging because they serve as protective factors. Many studies have revealed that being in these kinds of environments can help reduce the effects of negative cognitive aging. Successful cognitive aging is a multi-dimensional construct that describes how we can function optimally as we age. Therefore, it is necessary to reconsider our misconceptions of aging, and to think about the implications on social policy issues.
A common belief regarding aging is that “it is all downhill after our twenties”, but does it have to be so? Expressions like “you can’t teach an old dog new tricks” imply that as we age, we cannot learn new things. “Senile” and “slow” are adjectives we commonly use to describe the elderly. Aging is generally associated with cognitive impairment, such as having mobility issues, impaired perception, and memory loss. The list goes on, and the picture of aging remains unpleasant. An even more unpleasant fact is that many of these negative stereotypes about older adults are confirmed by laboratory studies – younger adults outperform older adults on a variety of cognitive tasks that measure attention, perception, memory, language, decision-making, and metacognition.
One fundamental change that happens as we age is age-related slowing: We are slower to process and react to things happening in our environment. This is an important factor that explains part of the difference between younger and older adults. Another key change with aging is the loss of inhibitory control, which is the ability to focus on a particular task and to ignore distractions. Inhibitory control becomes weaker as we age. For instance, in one study, scientists examined how younger and older adults recalled stories. Both groups read a story and told it back to an experimenter. Older adults tended to use filler sounds like ‘uh’ more than younger adults while retelling the story. Critically, even when both groups were explicitly told not to produce filler sounds, older adults still produced more filler sounds than younger adults.
A third important age-related change is the ability to remember. A well-known stereotype about older adults is that they have a harder time remembering things. The scientific parlance for the kind of memory people refer to when they say “memory” is episodic memory. However, memory itself has different types, and aging affects different types of memory differently. Aging impacts some kinds of memory negatively, like working memory, the ability to hold and use information in a temporary store (e.g., doing math in your head); prospective memory, remembering to perform a task in the future (e.g., taking medications at the right time); and episodic memory, memory for past episodes (e.g., remembering what you had for lunch yesterday). Older adults tend to show poorer working memory, prospective memory and episodic memory than younger adults. Yet aging impacts other kinds of memory positively, like procedural memory, the ability to perform tasks (e.g., tying your shoes); and semantic memory, memory for knowledge (e.g., knowing George Washington is the first president of the United States). Older adults tend to show just as good procedural memory as younger adults, and they have superior semantic memory compared to younger adults.
One way scientists talk about the different aspects of cognition is by talking about it in terms of crystallized and fluid intelligence. Crystallized intelligence refers to the accumulation of knowledge (i.e., procedural and semantic memory), while fluid intelligence refers to the infrastructure enabling us to accumulate that knowledge in the first place (i.e., processing speed, inhibitory control, working memory, prospective memory, episodic memory). In this manner, we can say that as we age, crystallized intelligence increases while fluid intelligence decreases. However, it is important to understand that these patterns depend on the novelty of the environment and the complexity of the task. Performance differences between younger and older adults are present especially when older adults perform more complex tasks and when they are in novel environments.
So far, we discussed what cognitive aging is, and largely focused on its negative impacts.
Recently, aging research has begun to provide an optimist view and introduced the concept of successful cognitive aging.
The concept itself is difficult to define, but we can demonstrate the idea of successful cognitive aging through a number of studies which has shown that cognitive aging is not a completely bleak prospect. Successful aging does not necessarily mean performing similar to the young population, but performing better in your same age group. Thus, it is not about rejecting the decline in cognitive abilities; it is about reserving the ability to function optimally on a daily basis, despite the decline previous research suggests.
Being in an intellectually stimulating environment is seen as one of the key factors of successful aging. A group in University of California, Berkeley, compared some cognitive abilities of senior professors with young adults, and for control purposes, with older adults who were not university professors. The results were intriguing: Although the scientists found the expected differences in inhibitory control between older adults and younger adults, these differences did not emerge when they compared senior professors and young adults. Senior professors were just good as young adults at inhibitory control, which suggests that the cognitively stimulating environment of academics served as a protective factor. No wonder why senior professors want to stay longer in the university – they benefit from the enriched environment themselves.
Another route towards successful aging is engaging in physical activity. The benefits of being physically active have been long-known: Consistent exercising reduces the risk of heart disease, of developing Type-2 diabetes, and of overall mortality. In the last 15 years, researchers have turned their attention toward the benefits of daily physical activity on cognition. Many studies have shown that physical exercise attenuates cognitive impairments and reduces the risk for developing dementia and Alzheimer’s – both of which are associated with old age. These findings open the door to training and intervention studies with older adults.
The basic empirical idea behind training studies was to introduce physical activities to a group of older adults and observe the neurological changes as they learn or continue their exercises. Researchers in this field believe that the brain is still plastic after the critical developmental period and is open to positive changes with the right interventions. They challenge the misconception of cognitive aging as an inevitable gray matter decline and a decrease in brain volume, and instead support a “use it or lose it” principle. As the name implies, it suggests that when we are not sufficiently engaged, the brain atrophies and loses plasticity. However, when we are sufficiently engaged, this leads to new neural connections and new wirings.
A research group in the Department of Neuroscience at University of Hamburg decided to test the “use it or lose it” principle by training older adults how to juggle with three balls. Juggling is a skill that requires good coordination and timing, and even younger adults have a hard time learning how to juggle. Out of the 67 older adults who were trained to juggle three balls for one whole minute, 25 of them achieved the goal after three months. The brain scans of these 25 older adults after learning how to juggle showed a larger gray matter density in the hippocampal region compared to their first scans, which directly contradicts previous findings showing smaller gray matter density with age.
A fascinating aspect of physical activity studies with older adults is that even though participants just engage in physical exercise training, their cognitive abilities (e.g., memory and attention) improve. Thus, the benefits of physical activity extend to cognitive abilities, even when participants are not specifically engaging in cognitive training during these interventions. Research reveals that when older adults go through regular aerobics exercises for weeks, their attention and information-processing skills improve along the way. It is important to remember the definition of successful aging at this point: These older adults still might not be performing as well as young adults; they are compared to themselves before beginning the intervention. In sum, they were able to fight back the negative changes associated with cognitive aging through physical exercise.
All these findings should encourage us to change our perspective of aging as a downhill road. The road is different for each individual, has great variability and there are possible hills along the way. Recently, a group in University of California, Los Angeles, identified a group of 80-year-olds, whose memory performance matched 50-year-olds, and named this group as the “super agers.” The discovery was amazing, because memory decline is one of the robust findings of normal aging. The neuroimaging data from the “super agers” revealed higher cortical thickness compared to their normal aged peers. This group represents the great variability among the old population in one of the most vulnerable domains, and creates the other end of the spectrum against associations of aging with dementia and Alzheimer’s disease. Clearly, for the “super agers”, the road has been straight for 30 years.
Successful aging studies are neither a promise of a youth fountain nor of immortality. They accept aging as a reality; however, they also claim that it is possible to function optimally with two key practices: cognitive stimulation and physical exercise. This brings up policy issues regarding aging: If staying both physically and mentally active is a protective factor, how should governments determine retirement age? How about the elderly living in countries with mandatory retirement policies? What are possible interventions after retirement? In the millennium era, it is crucial not to be misled by aging stereotypes, but to fully understand both sides of the coin.