As your dog grows older you might notice that he is showing lapses in memory and other behavioral changes. Similar to aging people, older dogs can suffer from a disorder called canine cognitive dysfunction syndrome, which is often compared to Alzheimer's disease in people because the symptoms are similar. These include forgetfulness, disorientation, not recognizing family members, sleep disruption and other lapses in normal mental behavior. Not only are the dog's behavioral symptoms similar to that to people with Alzheimer's disease, the changes that occur in the aging dog's brain are also similar. See Can Old Dogs Get Alzheimer's Disease?

Canine cognitive dysfunction is remarkably common and based upon the available data, it appears that 25 percent of dogs older than 10 years of age show at least one of the major symptoms associated with brain aging. In dogs 15 years of age, more than 60 percent are affected to some extent.

Nobody knows for sure what causes Alzheimer's disease or canine cognitive dysfunction, however, evidence has accumulated which suggests that an individual's lifestyle may be important. One of the most significant factors in avoiding the decline in thinking ability involves keeping mentally active. In humans people who engage in challenging mental activities, such as solving crossword puzzles, or playing games, engaging in new activities, taking courses, traveling, reading, or engaging in social activities with many different people, tend to be more likely to avoid the usual age related decline in mental ability. Norton Milgram, of the University of Toronto, has demonstrated that by keeping aging dogs mentally active, (in his lab he uses beagles), the effects of age related mental deterioration on learning and problem-solving can be greatly slowed, or even reversed.

For someone living with a pet dog, setting up new problems and experiences to keep your dog's aging brain from deteriorating can be a bit challenging, although it can be done (see Building a Better Brain for Your Dog). However, if we consider how and why evolution developed brains in the first place, a simpler alternative solution suggests itself.

If we could jump back into the dim past, say half a billion years ago, we would see the first nervous systems starting to appear. The original purpose for a nervous system was to coordinate movement, so an animal could go find food, instead of waiting for the food to come to it. Jellyfish and sea anemones, are similar to the first animals that created connected patterns of nerve cells to communicate to their musculature. This gave them a tremendous advantage over animals like sponges that waited brainlessly for dinner to arrive. It can be shown that animals which move quickly and frequently tend to have larger and more complex brains than similar classes of animals which are not as active. After millions of years of evolutionary experiment, nervous systems evolved some complex ways of going out to eat. However the goal of the brain remains the same, namely to coordinate movements. In this context it is interesting to note that a diminished ability to move is a good indication of the effects of aging. You might say that inflexibility heralds the approach of death, while a flexible body which is capable of making fluid movements that must be synchronized by an agile active brain, are the hallmarks of youth.


aging dog canine alzheimer's disease exercise

If this line of reasoning is correct, then perhaps increasing physical activity may help to strengthen the brain and offset the effects of aging in the same way that increasing mental activity does. Scientists already know from laboratory experiments that rats who spend a lot of time running in exercise wheels have better brains than their layabout lab mates. Their brains do not show as much shrinkage with age as their inactive comrades, and the effects are most marked on those areas of the brain that are often associated with memory functions and reasoning, such as the hippocampus and areas of the frontal and parietal lobes.

Exercise has been shown to affect human brains in the same way. Studies of senior citizens who walk regularly showed significant improvement in memory skills compared to sedentary elderly people. Walking also improved their learning ability, concentration, and abstract reasoning in people who walked as little as 20 minutes a day. Furthermore, research from the Salk Institute demonstrates that physical exercise has a protective effect on the brain and its mental processes, and may even help prevent Alzheimer's disease. Their data was based on exercise and health data from nearly 5,000 men and women over 65 years of age which showed that those who exercised were less likely to lose their mental abilities or develop dementia, including Alzheimer's.

Walking seems to be especially good for your brain because it increases blood circulation and the oxygen and glucose that reach your brain. Walking is not strenuous, so your leg muscles don't take up extra oxygen and glucose like they do during other forms of exercise. As you walk, you effectively oxygenate your brain. (Maybe this is why walking can "clear your head" and helps you to think better.) As in all kinds of movement and exercise, walking increases breathing and heart rate so that more blood flows to the brain, enhancing energy production and waste removal. Studies show that in response to exercise, cerebral blood vessels can grow, even in middle-aged sedentary animals.

A five-year study at the Laval University in Sainte-Foy, Quebec suggests that the more a person exercises the greater the protective benefits for the brain. Inactive individuals were twice as likely to develop Alzheimer's, compared to those with the highest levels of activity (exercised vigorously at least three times a week). But even light or moderate exercisers (a minimum of a 30 minute walk at least 3 times a week) reduced their risk significantly for Alzheimer's and mental decline. It is almost as if the brain has a built in pedometer and a mechanism where the more steps that you take, the higher the protective benefits to your brain, and lower your risk is for mental decline with age.

While the vast majority of the research has been done on rats and more recently on humans, Norton Milgram's research team at the University of Toronto has replicated many of these findings about the beneficial effects of exercise on the brain using dogs. There is certainly no reason to expect that the nervous system of dogs would respond differently than those of the other mammals that have been tested so far.

So the implications appear to be quite clear. If you have an aging dog and you want to offset the kinds of mental declines that we normally expect in older canines, or even if you have a senior dog who was beginning to show signs of memory loss or other symptoms of canine cognitive dysfunction, a simple way to slow the deterioration of his mind, and perhaps offset the effects of aging, involves simply clipping a leash onto your dog's collar and taking a walk. The more frequently you walk, and the longer the walks, the slower the mental decline with age. By the way, the research suggests that your brain will reap the same benefits, and the same protection from aging that your pet dog gets while you are walking him.

Stanley Coren is the author of many books including: The Modern Dog, Why Do Dogs Have Wet Noses? The Pawprints of History, How Dogs Think, How To Speak Dog, Why We Love the Dogs We Do, What Do Dogs Know? The Intelligence of Dogs, Why Does My Dog Act That Way? Understanding Dogs for Dummies, Sleep Thieves, The Left-hander Syndrome

Copyright SC Psychological Enterprises Ltd. May not be reprinted or reposted without permission.

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