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For several decades, people have used the term "use it or lose it" to aptly describe the best way to off-set the problems that come with aging. As overly simplistic as the idea sounds, scientific studies continue to show that if you disengage in later life, things fall apart. This has particular relevance when we're talking about cognitive performance.
For years, we assumed that cognitive performance declined substantially as a part of normal aging. However, recent research suggests, in fact, that is not the case. It is true that individuals with abnormal brain function who end up going on to get dementia show decline in cognition beginning as early as in their 40s and the decline during later life can be steep. But for those with normal brain matter, function, and activity, the average person does experience cognitive decline but there is potential for this to be quite modest. As we age learning new, novel information takes a bit more effort and time than earlier in life, but our foundation of knowledge and wisdom is far greater allowing us to understand a deep level of complexity about subjects we know well. So what can we do to greatly reduce decline whether it be due to impending pathology or normal aging?
There are no drugs to prevent you from getting Alzheimer's disease at this point. But, there is quite a bit of evidence that lifestyle greatly modifies the downward trajectory of cognitive performance as you age. A growing amount of research, including that done by Rohwedder and Willis (1), proposes that maintenance of cognitive performance takes practice, however. Evidence of this is most stark with regard to the effect of retirement. There is an impressive decrease in cognitive performance that comes with retirement, which researchers suggest is because when we stop engaging in cognitively complex tasks, the brain is no longer challenged enough to maintain cognitive function. It has been proposed that retirement is problematic because it results in a shift in environment in which we are no longer using our brains at a high level on a frequent basis. While staying in the work force longer might be an option and worth while for some, is it possible to do something to prevent this decline from occurring when we do go on to retire?
Scientific evidence on this issue is still emerging. Some studies suggest, for example, that volunteering at a very high level (i.e., 15 hours or more a week) may be a pathway for maintaining cognitive performance in post-retirement years (2). However, the research assessing the effect of volunteering on cognitive performance is inconsistent, probably because it depends on what kind of volunteering you're doing, and how much time you're doing it. What about brain games? There are others on this site who have discussed this at greater length, but a consensus of experts suggest that there is little evidence that brain games work (3). If they do provide a buffer to cognitive decline, it is not a robust long-term effect, and there is a potential cost that comes from engaging in brain games over other things that do positively effect your quality of life.
So if you're going to do something to help maintain your cognitive performance after you retire, what provides the greatest bang for your buck? Exercise. The effect of exercise on cognitive performance is impressive. Walking 200 minutes per week on average at age 70 has been shown to not only maintain (or improve) cognitive function, but it also results in an increase in the size of certain parts of the brain at a time when the brain is rapidly shrinking (4). In effect, exercise seems to reverse the effects of aging on the brain. And exercise is not only good for your brain. As long as you are engaging in ways that do not place you at risk for injury, exercise has the potential to treat your physical health as well or better than prescription drugs designed to manage chronic conditions like high blood pressure and high cholesterol, and is one of the single best ways to maintain your mental health, which also has an important effect on cognitive performance (5).
So, it isn't just about doing something relative to doing nothing as you age. Some ways of doing are better than others. Although the research is still underway, for those of us who are actively studying these issues, the best we can offer is this: working longer may not only be good for your finances and sense of purpose, it will also help you maintain your brain. Regardless of your age or retirement status, however, exercise is as much a way to stay physically fit as it is a way to stay mentally sharp.
References:
1. “Mental Retirement.” Rohwedder, S. & Willis, R. 2010. Journal of Economic Perspectives 24(1):119-38. NIHMS. doi: 10.1257/jep.24.1.119.
2. "Health outcomes of Experience Corps : A high-commitment volunteer program." Hong, SI & Morrow-Howell, N. 2010. Social Science and Medicine, 71, 414-420. doi:10.1016/j.socscimed.2010.04.009.
3. http://longevity3.stanford.edu/brain-health/expert-consensus-on-brain-h…
4. "Exercise training increases size of hippocampus and improves memory. Erickson, et al, 2011. PNAS. doi: 10.1073/pnas.1015950108.
5. "Comparative effectiveness of exercise and drug interventions on mortality outcomes: metaepidemiological study. Naci, H. & Loannidis, J. 2013. British Medical Journal. doi:10.1136/bjm.15577.
