MSD Manual

Please confirm that you are not located inside the Russian Federation

honeypot link

Effects of Aging on the Nervous System

By

Kenneth Maiese

, MD, National Heart, Lung, and Blood Institute

Last full review/revision Mar 2021| Content last modified Mar 2021
Click here for the Professional Version

Brain Brain The brain’s functions are both mysterious and remarkable, relying on billions of nerve cells and the internal communication between them. All thoughts, beliefs, memories, behaviors, and moods... read more Brain

Brain function varies normally as people pass from childhood through adulthood to old age. During childhood, the ability to think and reason steadily increases, enabling a child to learn increasingly complex skills.

During most of adulthood, brain function is relatively stable.

After a certain age, which varies from person to person, brain function declines. Some areas of the brain decrease in size by up to 1% per year in some people but without any loss of function. Thus, age-related changes in brain structure do not always result in loss of brain function. However, a decrease in brain function with aging may be the result of numerous factors that include changes in brain chemicals (neurotransmitters),changes in nerve cells themselves, toxic substances that accumulate in the brain over time, and inherited changes. Different aspects of brain function may be affected at different times:

  • Short-term memory and the ability to learn new material tend to be affected relatively early.

  • Verbal abilities, including vocabulary and word usage, may begin to decline later.

  • Intellectual performance—the ability to process information (regardless of speed)—is usually maintained if no underlying neurologic or vascular disorders are present.

Reaction time and performance of tasks may become slower because the brain processes nerve impulses more slowly.

As people age, the number of nerve cells Nerves The peripheral nervous system consists of more than 100 billion nerve cells (neurons) that run throughout the body like strings, making connections with the brain, other parts of the body, and... read more in the brain may decrease, although the number lost varies greatly from person to person, depending on the person’s health. In addition, some types of memory are more vulnerable to loss, such as memory that holds information temporarily. However, the brain has certain characteristics that help compensate for these losses.

  • Redundancy: The brain has more cells than it needs to function normally. Redundancy may help compensate for the loss of nerve cells that occurs with aging and disease.

  • Formation of new connections: The brain actively compensates for the age-related decrease in nerve cells by making new connections between the remaining nerve cells.

  • Production of new nerve cells: Some areas of the brain may produce new nerve cells, especially after a brain injury or a stroke. These areas include the hippocampus (which is involved in the formation and retrieval of memories) and the basal ganglia (which coordinate and smooth out movements).

People can influence how quickly brain function declines. For example, physical exercise seems to slow the loss of nerve cells in areas of the brain involved in memory. Such exercise also helps keep the remaining nerve cells functioning. On the other hand, consuming two or more drinks of alcohol a day can speed the decline in brain function.

As people age, blood flow to the brain may decrease by an average of 20%. The decrease in blood flow is greater in people who have atherosclerosis of the arteries to the brain (cerebrovascular disease). This disease is more likely to occur in people who have smoked for a long time or who have high blood pressure High Blood Pressure High blood pressure (hypertension) is persistently high pressure in the arteries. Often no cause for high blood pressure can be identified, but sometimes it occurs as a result of an underlying... read more High Blood Pressure , high cholesterol Dyslipidemia Dyslipidemia is a high level of lipids (cholesterol, triglycerides, or both) or a low high-density lipoprotein (HDL) cholesterol level. Lifestyle, genetics, disorders (such as low thyroid hormone... read more Dyslipidemia , or high blood sugar (diabetes mellitus Diabetes Mellitus (DM) Diabetes mellitus is a disorder in which the body does not produce enough or respond normally to insulin, causing blood sugar (glucose) levels to be abnormally high. Urination and thirst are... read more ) that is not controlled by lifestyle changes or drugs. These people may lose brain cells prematurely, possibly impairing mental function. As a result, the risk of damage to blood vessels leading to vascular dementia Vascular Dementia Vascular dementia is loss of mental function due to destruction of brain tissue because its blood supply is reduced or blocked. The cause is usually strokes, either a few large ones or many... read more at a relatively young age is increased.

Did You Know...

  • Physical exercise may slow the age-related decline in brain function.

  • Having uncontrolled high blood pressure, diabetes, or high cholesterol levels can speed the age-related decline in brain function.

Spinal cord Spinal Cord The spinal cord is a long, fragile tubelike structure that begins at the end of the brain stem and continues down almost to the bottom of the spine. The spinal cord consists of bundles of nerve... read more

As people age, the disks between the back bones (vertebrae) become hard and brittle, and parts of the vertebrae may overgrow. As a result, the disks lose some of their capacity to cushion, so more pressure is put on the spinal cord and on the branches of the nerves that emerge from it (spinal nerve roots). The increased pressure may injure nerve fibers at the point where they leave the spinal cord. Such injury can result in decreased sensation and sometimes decreased strength and balance.

Peripheral nerves Overview of the Peripheral Nervous System The peripheral nervous system refers to the parts of the nervous system that are outside the central nervous system, that is, those outside the brain and spinal cord. Thus, the peripheral nervous... read more

As people age, peripheral nerves may conduct impulses more slowly and release neurotransmitters is impaired, resulting in decreased sensation, slower reflexes, and often some clumsiness. Nerve conduction can slow because the myelin sheaths around nerves degenerate. Myelin sheaths are layers of tissue that insulate nerves and speed conduction of impulses (see figure Typical Structure of a Nerve Cell Typical Structure of a Nerve Cell The peripheral nervous system consists of more than 100 billion nerve cells (neurons) that run throughout the body like strings, making connections with the brain, other parts of the body, and... read more ).

Degeneration also occurs because as people age, blood flow decreases, nearby bones overgrow and put pressure on the nerves, or both. Age-related changes in function can become more noticeable when the nerves are injured by something else (for example, by diabetes mellitus).

The peripheral nervous system’s response to injury is reduced. When the axon of a peripheral nerve is damaged in younger people, the nerve is able to repair itself as long as its cell body, located in or near the spinal cord, is undamaged. This self-repair process occurs more slowly and incompletely in older people, making older people more vulnerable to injury and disease.

NOTE: This is the Consumer Version. DOCTORS: Click here for the Professional Version
Click here for the Professional Version
Others also read
Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID

Test your knowledge

Overview of the Autonomic Nervous System
The sympathetic nervous system is responsible for each of the following functions EXCEPT:
Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID

Also of Interest

Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID
TOP