There's a way that people in their seventies can protect themselves against neurological diseases of aging such as Alzheimer's. It costs nothing and it's environment friendly too: a daily walk of two kilometres or longer. Time needed: thirty minutes or more.
Studies show that physical exercise protects the brain. The way this works is pretty complex. Strength and cardio training make the heart and blood vessels stronger, and improve the blood supply to the brain cells. The brains direct the muscles and this is also 'training' for the brain cells. Physical exertion also boosts the production of growth factors like BDNF, and as a result of this the brain cells make more connections with each other.
Some studies have shown that training programmes help the brains of elderly people to grow, and others have shown that people who eat a healthy diet and get lots of exercise halve their likelihood of developing Alzheimer's. These findings are a real bombshell, as textbooks are still saying that the over-sixties lose several percent of their brain mass each year. But this process is apparently not as inevitable as neurologists thought.
Researchers at the University of Pittsburgh published the results of an epidemiological study of nearly three hundred over-65s in Neurology. The researchers worked out how many kilometres the subjects walked each day, and according to their answers divided them into four approximately equal-sized groups.
The people in Q1 didn't walk at all or only did so for a few minutes; the people in Q2 walked a little more; those in Q3 slightly more again; and those in Q4 walked 2-8 km per day, taking between 30 minutes and 2 hours to do so.
Nine years later the researchers made scans of the brains of their senior subjects. These showed that the precentral gyrus, the supplementary motor area [5 in the figure below], the precuneus and the hippocampus were all larger in Q4 than in the other groups.
Although the researchers could not demonstrate that the Q4 group functioned better mentally, they assume that physical exercise protects the brain against aging. Health advisors suggest half an hour exercise a day. According to this study, this would be a minimal indication for the brain. Taking less exercise has no effect.
And what about doing more than 2km/30 mins? Probably protects even more.
Neurology. 2010 Oct 19;75(16):1415-22.