In a yesterday’s blog, we discussed a study that provided powerful evidence that losing your driver’s license shortens your life. For individuals that were roughly matched for their physical health and brain health going into that study, an astounding 4-6X as many individuals who had given up driving had departed from this mortal coil, in comparison with their study mates who were still happily driving around town. “Drive or die”, was the clear message. In discussing this rather astonishing testament to ‘what matters’ in a modern American life, we noted that it was NOT driving per se that saved your bacon. It was your ability to stay actively engaged as a player in a continuously unpredictable and challenging ‘real world’ that (I believe) accounts for the difference.
There are several compelling animal studies that support what I’m talking about. House a rat in a cage in which it is provided with all the comforts and with all the food and water it wants and needs, and it will slowly deteriorate. By about 3 years of age, it can no longer feed itself very easily with its forepaws. Sensory information from those paws is greatly degraded, and the rat struggles to control them. By the time the rat dies, they can be almost-useless clubs.
Movements at an older age are slow and clumsy. If the rat is challenged to walk across a narrow bar or rope to feed itself, it struggles to maintain its posture and balance, and on about its 3rd birthday, can no longer cross such a bridge without falling off. A younger adult rat can run across a narrow wire if it smells the cheese!
The situation changes for an older rat, when their mental and physical life is made more challenging by creating a more complex physical and unpredictable environment for them. Physical and mental challenges richly engaged its cortex, and DEMAND that it call on its working memory to ‘solve’ innumerable new tasks that challenge it. When my friend Hubert Dinse reintroduced this kind of challenging life for older rats beginning not long before their 3rd birthday (equivalent to roughly your 65th birthday in human years) and shortly before they were expected to die of old age, they rapidly recovered more normal use of information from their paws, limbs and bodies. As a consequence, they retained their ability to feed themselves via more-agile forepaw use, and that narrow bridge presented no particular challenge to them on their 30-month birthday. AND (this is the important part), their life was extended by more than 3 months (more than 15%). Not because they were driving cars. But because they were still able to lead a rich, stimulating, continuously challenging life!
My UCSF colleague Etienne de Villers-Sidani has been conducting closely related studies, except that in his case, there is no particular PHYSICAL dimension to the rat’s exercise. His rats are being trained to make fine distinction about what they hear, in a rewarded, memory-requiring behavior that occupies about 1.5 hours out of each rat’s day. Rats near the end of life that are trained for several weeks are, similarly, much more lively and vigorous and healthy than are their brother rats who do not receive this training. We know that with such ‘cognitive’ training, we have extended their life-spans — although we’ve not yet precisely measured how many additional weeks or months result from the training.
You might note that neither one of these studies examined the very interesting question: If rich environmental challenges and a heavy daily dose of ‘cognitive training’ were a part of a person’s regular brain- and body-health regimen, how MANY years could we expect it to contribute to their lifespan?
These very interesting questions are now subjects for study in both aging rats and humans!!