The continuing economic doldrums have many of us casting a worried eye on our retirement accounts. But in order to assure ourselves of a comfortable old age, there’s another fund on which we should be keeping tabs—a mental one. Each of us should be asking ourselves: How deep is my cognitive reserve?
 
Cognitive reserve is the term scientists use to describe the extent of the brain’s capacity to resist aging and degenerative conditions like Alzheimer’s disease. The notion that such a capacity could exist originated in a surprising discovery made almost 25 years ago, when the brains of 137 elderly residents of a nursing home were dissected after their deaths.
 
Remarkably, researchers failed to find a direct relationship between the degree of Alzheimer’s disease detected in the residents’ brains (revealed by the presence of structures called plaques) and how impaired they had been while they were alive. In other words, some of these individuals were able to resist the ravages of the illness better than others—but how?
 
The neuroscientists from the University of California, San Diego, reported that the subjects whose abilities were less affected by Alzheimer’s were those with bigger brains and a greater number of neurons—suggestive evidence that keeping their brains active had built a bulwark against decline.
 
Since then, the idea that a deep cognitive reserve provides protection against mental aging has received ever more support. The latest study, to be published in the journalNeurology, was posted online this month. A team led by Robert Wilson of Rush University Medical Center in Chicago enrolled almost 300 elderly people, testing their thinking and memory skills each year as they grew older. The researchers also asked participants about how often they read, wrote, and engaged in other mentally stimulating activities—not just currently but in childhood, young adulthood and middle age.
 
Following each participant's death his or her brain was examined, and after accounting for physical evidence of dementia, the scientists produced an amazing finding: people who made a lifelong habit of lots reading and writing slowed their rate of mental decline by 32 percent over those who engaged in only average levels of these activities. Compared to the average folks, people who rarely read or wrote experienced a decline that was 48 percent faster.
 
Reading and writing aren’t the only ways to augment your cognitive reserve. Research on bilingualism by Ellen Bialystok of York University in Toronto, for example, has demonstrated that speaking more than one language delays the onset of Alzheimer’s symptoms by an average of five years. Bialystok theorizes that the mental exercise required to speak multiple tongues—remembering which word belongs to which language—helps bilinguals build up their mental storehouse.
 
And Nina Kraus of Northwestern University has found that people who spend many years practicing a musical instrument are better able to respond quickly and accurately to sounds that they hear. Kraus reported that middle-aged musicians outperformed not only their non-musician peers but also non-musicians many years their junior. The mental rigor required by the practice of music effectively acted as an antidote to aging, keeping their nervous systems youthful.
 
We’ve all been taught the importance of beginning early in saving money for retirement. Accumulating mental capital—by reading and writing, speaking a second language, or practicing a musical instrument—works the same way. If you want a generous cognitive reserve to see you through your golden years, you’d better start contributing now.