Physical Exercise and HD
Part 2

Exercise and Cognitive Maintenance

Even people who do not have HD experience a moderate amount of neurodegeneration as part of the normal aging process. Here, the signals that nerve cells use to communicate with one another become less powerful and less efficient. This decreased ability for nerve cells to communicate makes it harder for the brain to adapt to outside influences and generate new nerve cells. The inability to create new nerve cells leads to losses in brain tissue and impaired functioning. Indeed, imaging studies in elderly humans have shown some noticeable atrophy in the brain. In people with HD, this atrophy is substantially magnified. One of the consequences of atrophy is that older adults typically perform more poorly than younger adults on a broad range of cognitive measures. (For more information on cognitive symptoms of HD, click here)

Despite such declines in cognitive and motor processes during the course of aging in people with HD, recent findings suggest that physical exercise can minimize some, but not all, kinds of cognitive decline. A recent study showed that older adults who exercised throughout life had less brain tissue loss and performed significantly better on cognitive tests than adults who exercised infrequently. Similarly, a study with twins done in Sweden found that the twin who exercised more was also more likely to score higher on a cognitive test. It is important to note that these tests show correlation and do not necessarily prove causation. In other words, just because people who exercise a lot show increased cognitive abilities, this does not necessarily mean that one causes the other. For example, people who exercise more may also have better eating habits such that improved nutrition leads to better cognitive scores. Nevertheless, as indicated by the numerous studies discussed below, the role of exercise in cognitive maintenance should not be discounted.

It turns out that the areas in the brain that are associated with mental decline due to aging are the same areas that are the most responsive to exercise. Researchers have found that people who exercise a lot have more gray matter and white matter in the brain, particularly in the frontal lobe, temporal lobe, and parietal lobe. The lobes of the brain are composed of gray matter and white matter. Gray matter is where all the nerve centers are located. White matter connects the gray matter together. (For more information about the brain and its structures, click here.) The amount of gray matter and white matter declines naturally, affecting the functioning of the lobes and contributing to a decline in cognitive functioning and processing ability.

It has been found that individuals with HD typically have a substantially reduced volume of gray matter and white matter in the brain, especially in the temporal lobe and the frontal lobe. This is significant, given the prominent roles that each of these lobes play in the cognitive processes. The frontal lobes of the brain have a lot to do with what people call higher-level cognition, where we synthesize information, and store data we've just acquired. If the frontal lobes are not functioning properly, then you can easily forget a phone number you just looked up or the name of a person you just met. The temporal lobes consolidate short-term memories and build them into long-term memories. Damage to temporal lobes can also result in altered personality and affective behavior. The parietal lobes allow us to construct a spatial coordinate system to represent the world around us. Damage to the parietal lobes can result in neglecting part of the body or space, which can impair many self-care skills such as dressing and washing. (For more information about the lobes of the brain, click here.) Deterioration of each of these lobes is associated with some sort of mental decline. Exercise appears to exert its effects partially by protecting against a loss of gray matter and white matter, thereby preserving the structure and function of the lobes in the brain. With the lobes able to function better, the onset and progression of various cognitive deficits are likely to be delayed.

The fact that some degree of neurodegeneration is part of the normal aging process means that a person with HD must deal with these changes in addition to disease-related loss. Preserving cognitive function and preventing mental decline is definitely an uphill battle and some amount of neurodegeneration is inevitable. But this does not mean that the situation is hopeless. Studies on exercise reveal that it may indeed play an influential role in slowing down cognitive decline. As the rest of this chapter reveals, exercise exerts numerous other beneficial effects throughout the body and is thus a wonderful practice to incorporate into the daily routine. Later in this chapter, we’ll give some suggestions for where to begin.

Click here to return to "Lifesytle and HD: An Introduction to Life Practices That Promote Health."

Last Modified: 04/12/2007

An educational product of HOPES, not to be used in place of medical care. For more information about HOPES, click on the Logo. To contact HOPES with comments or questions, click here.