As the saying goes, "Growing old isn't for whimps." Besides the challenge of coping with physical changes, as discussed in my blog of 2/1/11, there is also the challenge of possibly losing your mind, or at least not being able to remember where you put it. Sad personal reminders of this are several academic colleagues of mine who are now in various stages of Alzheimer's, a disease made all the more tragic for these people because they were all bright, well-educated intellectuals with incisive minds.
Alzheimer's is the most prevalent form of dementia, followed by dementia produced by strokes. And it is indeed prevalent. According to the Alzheimer's Association, 5.4 million Americans have the disease. At age 65 the estimated lifetime risk of developing Alzheimer's or some other form of dementia is 20% for women and 17% for men. For those who make it to 85, the risk is much higher -- 43%. And it is indeed deadly. Alzheimer's is currently the 6th leading cause of death in this country, 5th for those over 65. It is estimated that 61 percent of people with Alzheimer’s at age 70 will die before age 80 compared with 30 percent of people at age 70 without the disease.
An optimistic take on these grim statistics is that most geezers won't be stricken by Alzheimer's or other forms of dementia during their "golden years" -- if 20% are afflicted, then the other 80% won't be, right? While this optimism is justified in the strictest sense, there is now a substantial body of scientific evidence that even "normal" geezers will experience some degree of cognitive decline due to changes in neurological processes and brain structure that are an inevitable result of aging. These physical changes will likely be manifested in difficulties in learning, reasoning, decision making, cognitive task performance, and memory. The evidence also shows, though, that there is a wide range among individuals in the type and degree of difficulties they experience, even among those with the same degree of neurological degradation. A more realistic approach then, is to ask "how much cognitive decline will I experience and is there anything I can do about it?"
The most recent research bearing on these questions has been nicely summarized and evaluated by Christopher Hertzog in a monograph published by the Association for Psychological Science (Hertzog et.al., 2008). Hertzog's analysis of the available data suggests that there are a number of identifiable factors that influence a person's degree and rate of decline, and that there are certain interventions that can -- within limits -- alter an individual's position within the possible range of functioning.
It is important to note that the evidence for some of these "enrichment effects" is not very strong or is controversial, while for other factors the research seems much clearer and stronger. For example, it is somewhat surprising that the common sense idea of staving off cognitive decline by leading an intellectually active lifestyle (the "use it or lose it" hypothesis) -- while it has received consistent empirical support -- must be tempered by the fact that the strength of the effect is not as strong as it is for other factors and may be open to alternative explanations (Hertzog et. al., 2008). Nonetheless, research over the last 10 years indicates that continued engagement in mentally stimulating activities (reading books, attending plays, playing chess, writing, playing a musical instrument, attending public lectures, taking courses, etc.) can reduce the debilitating effects of "normal" cognitive decline, and even lower the risk of dementia and Alzheimer's disease (Wilson et. al, 2007).
Another approach to cognitive enrichment is based on what might be called the "mental pushup" model., where older people are exposed to interventions that involve specific training in memory, reasoning, or problem solving. For example, in a study by Ball et al. (2002), 2500 participants over 65 went through training sessions in one of three cognitive domains: memory, reasoning, or visual search. The results showed marked gains for each training group that persisted over a 5-year follow up period. As encouraging as these results seem, it was also found that the enhancement effects didn't transfer to performance-based measures of everyday problem solving or everyday speed of processing -- in other words, the benefits were restricted to the specific training domains and didn't generalize to other kinds of tasks. A number of other studies have reached the same conclusion -- very little generalization of the cognitive gains achieved by training specific skills or processes (Hertzog et al., 2008).
However, there have some very recent attempts to develop training strategies involving more complex mechanisms that do show generalization. One example is training in quickly switching between different tasks or between different sets of cues relevant to the same task, both of which are abilities involving cognitive control that usually decline significantly with age. In a study by Karbach & Kray (2009) this type of intervention not only significantly improved older adults' task-switching performance, but also produced generalized improvements in verbal and spatial memory, and reasoning skills.
Another promising new approach is "metacognition" training. "The essential feature of metacognitive interventions is to train individuals to assess processing demands of task contexts and to select, implement, and evaluate strategies during performance" (Hertzog et al., 2008, p. 20). For example, one metacognitive approach trains people on using mnemonic memory techniques coupled with self-testing to determine when material has been learned well enough to permit later retrieval (Dunlosky et al., 2007). Research indicates that the generality of this technique enables older people to apply it to everyday situations outside the experimental context.
As promising as some of these training strategies are, there is one type of intervention that recent research shows is hands down the most effective in lessening cognitive decline associated with aging: physical activity. It even seems to "compress cognitive morbidity" so that the period of diminished mental capacity is shorter, even among those with Alzheimer's and other forms of dementia (I discussed compression of morbidity regarding physical aspects of aging in an earlier blog).
The fitness fanatics out there no doubt are vigorously nodding their heads in agreement as they read this before their spinning class or after their 15-mile run. But the real news in this research is that (a) the level of physical activity required to achieve significant benefits is really quite modest, and (b) beneficial effects can be achieved even when the physical activities are initiated later in life. This is particularly encouraging for those geezers who have physical limitations or injuries that prevent them from engaging in high impact aerobics, or for those who weren't physically active in their younger years.
For example, in a study by Kramer et al. (1999) older adults who were in good health but sedentary were randomly assigned to either a training condition in which they walked briskly for 1 hour per day 3 days a week for 6 months, or a condition in which they performed stretching and toning exercises for the same amount of time. Those in the walking condition but not the stretching and toning condition showed generalized improvement in various aspects of cognitive functioning, including the ability to selectively process task-relevant information while ignoring irrelevant information, the ability to override inappropriate responses, and the ability to switch rapidly between multiple tasks.
In another example, the activity levels of 6,000 women aged 65 and older were assessed (e.g, blocks walked per week, flights of stairs climbed per day, frequency and duration of various exercise and sports activities) and then levels of cognitive functioning were measured 6-8 years later (Yaffe et al., 2001). Those who were more active were 30% less likely to show cognitive decline, even after adjusting for education level, health status, and other rival explanations. Interestingly, walking distance was related to cognitive functioning whereas walking speed was not, suggesting that even moderate levels of activity have a beneficial effect.
Finally, a number of studies have found that modest physical activity and exercise can reduce the probability of severe cognitive problems in later life. Rovio (2005), for instance, found that physical activity in middle age consisting of as little as 20-30 minutes twice per week of exercise vigorous enough to produce breathlessness and sweating reduced the risk of dementia 20 years later by 52%.
After evaluating all of the available research regarding cognitive functioning in older adults, including the studies focusing on physical activity, Hertzog et al. (2008) offers this optimistic conclusion:
"What is most impressive to us is the evidence demonstrating benefits of aerobic physical exercise on cognitive functioning in older adults. Such a conclusion would have been controversial in the not-too-distant-past, but the evidence that has accumulated since 2000 from both human and animal studies argues overwhelmingly that aerobic exercise enhances cognitive function in older adults. The hypothesis of exercise-induced cognitive-enrichment effects is supported by longitudinal studies of predictors of cognitive decline and incidence of dementia, but also by short-term intervention studies in human and animal populations. The exercise-intervention work suggests relatively general cognitive benefits of aerobic exercise but indicates that cognitive tasks that require executive functioning, working memory, and attentional control are most likely to benefit." (p.41)
Geezerhood is tough. But thanks to increases in our scientific understanding of aging, we are seeing some real advances in practical ways to come to terms with it. Cognitive decline may be inevitable, and for some us it will be devastatingly severe. But thankfully there are ways we can lessen the degree to which the quality of our lives are impacted by the relentless march of time.
References:
Ball, K., Berch, D.B., Helmer, K.F., Jobe, J.B., Leveck, M.D., Marsiske, M. (2002. Effects of cognitive training interventions with older adults: A randomized controlled trial. Journal of the American Medical Association, 288, 2271-2281.
Dunlosky, J., Cavallini, E., Roth, H., McGuire, C.L., Vecchi, T., & Hertzog, C. (2007). Do self-monitoring interventions improve older adults' learning? Journal of Gerontology: Psychological Sciences, 62B (special issue I), 70-76.
Hertzog, C., Kramer, A.F., Wilson, R.S., & Lindenberger, U. (2008). Enrichment effects on adult cognitive development: Can the functional capacity of older adults be preserved and enhanced? Psychological Science in the Public Interest, (9).
Karbach, Julia, & Kray, Jutta (2009). How useful is executive control training? Age differences in near and far transfer of task-switching training. Developmental Science, 978-990.
Kramer, A.F., Hahn, S., Cohen, N.J., Banich, M.T., McAuley, E., Harrison, C.R., et al. (1999). Aging, fitness and neurocognitive function. Nature, 400, 418-419.
Rovio, S., Kareholt, I., Kelkala, E.I., et al. (2005). Leisure time physical activity at midlife and the risk of dementia and Alzheimer's disease. Lancet Neurology, 4, 705-711.
Yaffe, K., Barnes, D., Nevitt, M., Lui, L.Y., & Covinsky, K. (2001). A prospective study of physical activity and cognitive decline in elderly women. Archives of Internal Medicine., 161, 1703-1708.
Wilson, R.S., Scherr, P.A., Schneider, J.A., Li, Y., & Bennett, D.A. (2007). The relation of cognitive activity to risk of developing Alzheimer's disease. Neurology, 69, 1911-1920.
