Although normal changes occur with age in the brain and nervous system, many people have misconceptions about the nature and extent of these changes. A common mistaken belief is the idea that all elderly people become senile. Many people blame increased confusion on "getting old" when it may, in fact, be caused by an illness.

The nervous system has two divisions. The central nervous system consists of the brain and spinal cord. It processes nerve messages and controls movement, thought and behavior. The peripheral nervous system is made up of the nerves coming to and from the spine (spinal nerves) and the nerves in the body. This portion of the nervous system carries sensory and movement messages to and from the central nervous system.

PHYSICAL CHANGES OF AGING
As people age, nerve cell mass is lost. This causes atrophy of the brain and spinal cord. Brain weight may decrease significantly from the maximum weight of young adulthood.

The number of nerve cells decreases, and each cell has fewer "branches" (dendrites). Some nerve cells lose their coating in a process called demyelinization. These changes slow the speed of message transmission.

After a nerve carries a message, there is a short time when it must rest and cannot carry another message (called the latency period). Aging increases the latency period.

Waste products from atrophied nerve cells may collect in the brain tissue, causing plaques and tangles. Lipofuscin (a fatty brown pigment) may also accumulate in nervous tissue.

These changes are not consistent in everyone. Some people have many physical changes in their nerves and brain tissue, others have few. Some will have atrophy and plaques, some will have plaques and tangles, and some will have other changes.

Although certain changes are typical of specific brain disorders, the amount and type of physical changes is not always clearly related to changes in brain function. For example, plaques and tangles are associated with Alzheimer's disease, but some people with the most severe symptoms have fewer plaques and tangles than those who have mild or moderate symptoms.

EFFECT OF PHYSICAL CHANGES
Some slight slowing of thought, memory, and thinking seems to be a normal part of aging. There is evidence that continued, moderate physical and mental exercise is helpful in maintaining cognitive abilities.

Physical aging changes are not clearly related to decreased brain or spinal cord function. Changes in memory, thought, and other cognitive functions, while common in the very old, cannot be directly traced to atrophy or other physical brain changes.

As nerves degenerate, the senses may be affected. Reflexes may be reduced or lost. Reflex changes increase problems with mobility and safety. Conversely, some reflexes that were present at birth and then lost through maturity (infantile reflexes such as the sucking reflex and grasp reflex) may reappear with advanced age. This may be a normal change or, more likely, may be a sign of a neurological disorder.

COMMON NERVOUS SYSTEM PROBLEMS IN THE ELDERLY
Delirium, dementia, and severe memory loss are NOT normal processes of aging. They can, however, be caused by degenerative brain disorders such as Alzheimer's disease.

Illnesses unrelated to the brain can also cause significant changes in thinking and behavior. For example, almost any infection can cause an older person to become severely confused. Another common cause of temporary difficulties with thinking and behaviour is the dysregulation of glucose and metabolism in patients with diabetes. Fluctuations in glucose levels can cause thinking disturbances.

Significant changes in memory, thought, ability to perform a task, and so on should be discussed with your health care provider, especially if these symptoms occur suddenly or along with other symptoms. A change in thinking, memory, or behavior is considered "significant" if is noticeably different from previous patterns, or if it affects lifestyle.

PREVENTION
There is some evidence that continued physical and mental activity helps to keep cognitive abilities (thinking, reasoning, and so on) sharp. Reading, doing crossword puzzles, and engaging in stimulating conversations -- as well as ordinary physical exercise -- may all help to keep your brain as sharp as possible.

RELATED TOPICS

• Aging changes in organs, tissues, and cells
• Aging changes in the senses