Memory Loss Health Article

Definition

Memory loss can be partial or total. Most memory loss occurs as part of the normal aging process. However, memory loss may also occur as a result of severe emotional trauma or due to brain damage following disease or physical trauma. Memory loss can be described as amnesia, forgetfulness, or impaired memory.

Description

Memory is often classified as immediate (retention of information for a few seconds); short-term (retention of information for several seconds or minutes); and longterm (retention of information for days, weeks, or years). In short-term memory loss, patients can remember their childhood and past events but fail to remember events that happened in the past few minutes. In long-term memory loss, patients are unable to recall events in the remote past.

Depending on the cause, memory loss can be sudden or gradual, and it can be permanent or temporary. Memory loss resulting from trauma to the brain is usually sudden and may be permanent or temporary. On the other hand, age-related memory loss, such as in Alzheimer's disease, occurs gradually and is usually permanent. It is barely noticeable at first, but progressively gets worse.

In most cases, memory loss is temporary and usually affects memories relating to a portion of a person's experience. However, severe physical brain trauma, such as that following a severe head injury, can cause total (global) memory loss. Some patients may temporarily lose memory and consciousness, then fully recover after the event.

Causes & symptoms

The following are common causes of memory loss:

• Aging. A person loses nerve cells at the rate of 1% per year, even without a disease associated with memory loss, such as Alzheimer's disease. The body stops growing new nerve cells after age 25. Therefore, by the time a person reaches 70 years of age, he or she will probably have lost at least one-third of his or her memory functioning.
• Nutritional deficiency. Not enough thiamine (vitamin B₁), vitamin B₁₂, and/or protein contributes to memory loss.
• Depression. Depression can cause memory loss at any age. This is one of the main reasons for forgetfulness in the elderly. Depression-related memory loss is a treatable condition.
• Diseases. Memory loss can result from such chronic disease conditions as diabetes or hypothyroidism.
• Oxygen deprivation. Such conditions as severe head trauma, surgery, strokes, or heart attacks cause a sudden reduction of oxygen to the brain, which causes widespread death of nerve cells and significant memory loss.
• Structural abnormalities in or damage to the parts of the brain associated with memory formation. As of 2003, researchers have identified the areas of the brain known as the hippocampus and the orbitofrontal cortex as the primary locations of memory formation.
• Free-radical damage. Free-radical molecules destabilize other molecules around them, resulting in damage to the body at the molecular level. Free-radicals can damage the blood-brain barrier, a membrane that separates the circulating blood and the brain. A weakened barrier may not be able to prevent toxic chemicals from entering the brain. Widespread brain damage, accelerated cell death, and memory loss occur as a result.
• Chemical poisoning. Daily exposure to toxic chemicals such as alcohol, tobacco, and illicit drugs (heroine, cocaine, and amphetamines) destroys brain cells at a rapid rate. Other environmental toxins, such as lead and mercury, can penetrate the blood-brain barrier. Once inside the brain, these heavy metals kill nerve cells. This helps explain why exposure to heavy metals has been linked to memory and learning problems in children. Even though aluminum is not considered a heavy metal, its accumulation in the brain is believed to contribute to Alzheimer's disease.
• Central nervous system (CNS) infections and inflammation of the brain. Encephalitis (an inflammatory disease of the brain) can result in the death of nerve cells, which can result in significant memory loss. CNS infections such as toxoplasmosis and neurosyphilis can also cause significant brain damage and memory loss.
• Stress. Emotional or physical stress stimulates the release of stress hormones such as cortisol and adrenaline. Constant exposure to stress hormones results in nerve-cell death and memory loss.
• Sensory overload. When a person is trying to do too many tasks or worry about too many things at the same time, the brain is overloaded with information and cannot process short-term memories. Therefore, if a person is trying to remember a lot of information, he or she tends to forget car keys or scheduled appointments.
• Low blood sugar. Nerve cells require glucose (sugar) to generate energy. If there is not enough glucose in the blood, nerve cells starve and die. Excessively low blood sugar can send a person into shock and/or into a coma.
• Genetic factors. Several genes that increase a person's risk of developing Alzheimer's were identified in 2002. In addition, Down's syndrome, which is caused by an abnormal form of human chromosome 21, is characterized by loss of memory relatively early in life, often in the patient's 30s or 40s.
• Seizures. Prolonged seizures, such as in patients with epilepsy, can cause significant memory loss.
• Severe emotional trauma. Extreme emotional trauma has been associated with sudden amnesia. Dissociative amnesia is a type of amnesia that occurs when the brain splits off, or dissociates, extremely distressing memories from conscious recollection.
• Low estrogen levels in postmenopausal women. Women often report a significant decrease in memory function immediately following menopause.