If you forget to pick up your dry cleaning once or twice, it’s unlikely that dementia is around the corner (although your favor-ite silk dress may be). Letting a few errands slip isn’t a sure sign of the disease. Healthy aging tends to impair recollection but not familiarity. Really important symptoms include loss of control over speech, trouble completing simple tasks like balanc-ing a checkbook, and confusiep about where you are.
In humans, exercise improves what scientists call “executive function”, the 5et of abilities that allows you to select behaviour that’s appropriate to the situation, inhibit inappropriate behaviour and focus on the job at hand in spite of distractions. Executive function includes basic functions iike processing speed, response speed and working memory, the type used to remember a house number while walking from the car to a party.
Executive function starts to decline when people reach their 70s. But elderly people who have been athletic all their lives have much better executive function than sedentary people of the same age. This relationship might occur because people who are healthier tend to be more active, but that’s not the whole story. When inactive people get more exercise, even starting in their 70s, their executive function improves, as shown in a recent meta-analysis of 18 studies.
Exercise is also strongly associated with a reduced risk of dementia late in life. People who exercise regularly in middle age are one-third as likely to get Alzheimer’s disease in their 70s as those who did not exercise. Even people who begin exercising in their 60s have their risk reduced by half.
How might exercise help the brain? In people, fitness training slows the age-related shrinkage of the frontal cortex, which is important for executive function.
In rodents, exercise increases the number of capillaries in the brain, which should improve blood flow, and therefore the availability of energy, to neurons. Exercise may also help the brain by improving cardiovascular health, preventing heart attacks and strokes that can cause brain damage. Finally, exercise causes the release of growth factors, proteins that increase the number of connections between neurons, and the birth of neurons in the hippocampus, a brain region important for memory. Any of these effects might improve cognitive performance, though it’s not known which ones are most important.
Researchers haven’t figured out what form of exercise best fits the bill yet, but right now they believe any aerobic workout or an intensive strength-training regimen is great. Both get oxygen flowing to the brain. For starters, try walking briskly for 30 to 60 minutes several times a week.