Aging is unavoidable - except perhaps for the brain, say researchers. They also present counterintuitive evidence that it is what you do in old age that matters when it comes to maintaining a youthful brain - not what you did earlier in life.

Education alone won't save your brain; PhDs are as likely as high school dropouts to experience memory loss with old age. Don't count on your job either - those with a complex or demanding career may enjoy a limited advantage, but those benefits quickly dwindle after retirement.

Instead, engagement is the secret to success. Those who are socially, mentally and physically stimulated reliably show greater cognitive performance with a brain that appears younger than its years.

"Although some memory functions do tend to decline as we get older, several elderly show well-preserved functioning and this is related to a well-preserved, youth-like brain," says Lars Nyberg, Professor of Neuroscience at Umeå University in Sweden. "There is quite solid evidence that staying physically and mentally active is a way towards brain maintenance."

The researchers say this new take on successful aging represents an important shift in focus for the field. Much attention in the past has gone instead to understanding ways in which the brain copes with or compensates for cognitive decline in aging. The research team now argues for the importance of avoiding those age-related brain changes in the first place. Genes play a role, but life choices and other environmental factors, especially in old age, are critical.

Elderly people generally do have more trouble remembering meetings or names, Nyberg says. But those memory losses often happen later than many often think, after the age of 60. Older people also continue to accumulate knowledge and to use what they know effectively, often to very old ages.

"Taken together, a wide range of findings provides converging evidence for marked heterogeneity in brain aging," the scientists write. "Critically, some older adults show little or no brain changes relative to younger adults, along with intact cognitive performance, which supports the notion of brain maintenance. In other words, maintaining a youthful brain, rather than responding to and compensating for changes, may be the key to successful memory aging."

Citation: L Nyberg, M Lövdén, K Riklund, U Lindenberger, L Bäckman. Memory aging and brain maintenance. Trends in Cognitive Sciences, April 27th 2012.