The reason I'm so enthralled to see seniors exercise is because it is the single best thing they can do to preserve their brains. Today's paper highlights recent research done in California that shows just that.
First, a bit of background. You have a gene called APOE (mice also have it). It comes in 3 flavors, and each person only has one of the three: APOE2 (not important for today’s article), APOE3 and APOE4. If you got lucky and scored the APOE3 kind, all is well. If you happen to be in the 20-25% of the population who has the APOE4 kind, you may be in trouble: APOE4 is a known risk factor for Alzheimer's disease. Does it mean you'll for sure get Alzheimer’s disease? No, but you are 10 to 30 times more at risk of developing Alzheimer's disease if you carry the APOE4 gene.
In this paper, researchers compared old APOE3 (normal) and APOE4 (at risk for dementia) mice. In general, aged APOE4 mice experience cognitive decline faster and earlier than APOE3 mice. The researchers were interested in studying whether exercise (running on a mouse wheel!) had any effect on this cognitive decline.
The researchers used cognitive tasks that rely on a part of the brain that's important for memory, the hippocampus. One of the tasks, called place recognition, involves putting a mouse in an arena with two objects. The mouse is then removed from the arena, one object is moved, and the mouse is put back in the arena. Presumably, a normal mouse will then spend more time exploring the object in the new location. For this task, the aged APOE4 mice were initially impaired compared with the APOE3 mice. This means that during the second trial of the task, they tended to explore both objects for similar amounts of time, instead of spending more time on the object at the new location. This result suggests that the APOE4 were unable to remember the initial object locations well. The good news? Mice who exercised did significantly better at this task. Interestingly, this was valid for both APOE3 and APOE4 mice. Even more interestingly, exercise improved the scores of both types of mice for all the tasks that tested the hippocampus.
What's going on in the brains of these exercising mice? It is thought that exercise increases the levels of a protein called BDNF (for Brain-Derived Neurotrophic Factor). BDNF regulates many important functions in the brain, including the making of new neurons and the making of new connections between neurons, and these effects are thought to be important for memory.
Regular readers of Scientific Chick know not to get too excited when I report about animal studies. Well, I'm happy to add that the results that were observed in those mice were also observed in humans. In fact, there are countless human studies out there that confirm that physical activity is a powerful way to improve and maintain your cognitive abilities.
When I try to urge certain people to exercise (you know who you are), I almost always hear the same excuse: “Well, my uncle so-and-so never got off his couch and he lived to be 100!” In some cases, heredity can be on your side, that's true. But genetics can be quite the lottery, and it's important to keep in mind that several forms of cognitive decline, including the most common form of Alzheimer's (called “sporadic” in scientific lingo) are not hereditary.
So to all my older readers out there, I'll see you on the road at next year's BC Seniors Games. And if you're not ready for cycling, there's always the cribbage category.
Reference: Exercise improves cognition and hippocampal plasticity in APOE epsilon4 mice. (2009) Nichol K, Deeny SP, Seif J, Camaclang K, Cotman CW. Alzheimers Dement. 5(4):287-94.