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Memory Loss

by Michael C. Levin, MD

Memory loss is one of the most common reasons that people, particularly older people, visit a doctor. Sometimes family members notice and report the memory loss. The biggest concern for the person, family members, and doctors is usually whether the memory loss is the first sign of Alzheimer disease, a progressive and incurable form of dementia (a type of brain disorder). People with dementia have lost the ability to think clearly. Usually, if people are aware enough of their memory loss to be concerned about it, they do not have early dementia.

Memories may be stored in short-term or long-term memory, depending on what they are and how important they are to the person. Short-term memory holds a small amount of information that a person needs temporarily, such as a list of things to buy at the grocery store. Long-term memory, as the name suggests, stores memories (such as the name of the person's high school) for a long time. Short-term memory and long-term memory are stored in a different parts of the brain. Long-term memory is stored in many areas of the brain. One part of the brain (the hippocampus) helps sort new information and associate it with similar information already stored in the brain. This process turns short-term memories into long-term memories. The more often short-term memories are recalled or rehearsed, the more likely they are to become long-term memories.

Causes

Common causes

The most common causes of memory loss are

  • Age-related changes in memory (most common)

  • Mild cognitive impairment

  • Dementia

  • Depression

Age-related changes in memory refer to the normal slight decline in brain function that occurs as people age. Most older people have some memory problems. Retrieving memories of new things, such as what is a new neighbor's name or how to use a new computer program, takes longer. Older people also have to rehearse new memories more often for the memories to be stored. People with this type of memory loss occasionally forget things, such as where they left their car keys. But for them, unlike people with dementia, the ability to do daily activities or to think is not impaired. Given enough time, these people usually remember, although sometimes later than is convenient. This type of memory loss is not a sign of dementia or early Alzheimer disease.

Mild cognitive impairment is an imprecise term used to describe impairments in mental function that are more severe than normal age-related changes but less severe than those caused by dementia. Memory loss is often the most obvious symptom. People with mild cognitive impairment have trouble remembering recent conversations and may forget important appointments or social events, but they typically remember past events. Attention and the ability to do daily activities are not affected. However, about half of people with mild cognitive impairment develop dementia within 3 years.

Dementia is a much more serious decline in mental function (see Dementia). Memory loss, particularly for recently acquired information, is often the first symptom, and it becomes worse with time. People who have dementia may forget entire events, not just the details. They have difficulty remembering how to do things they have done many times before and how to get to places they have often been to. They can no longer do things that require many steps, such as following a recipe. People may forget to pay bills or keep appointments. They may forget to turn off a stove, lock the house when they leave, or take care of a child left in their care. They are unaware of their memory loss and often deny that they have such loss. Finding the right word, naming objects, understanding language, and doing, planning, and organizing daily activities become more and more difficult. People with dementia eventually become disoriented, not knowing what time or even what year it is or where they are. Their personality may change. They may become more irritable, anxious, paranoid, inflexible, or disruptive.

There are many forms of dementia. Alzheimer disease is the most common (see Alzheimer Disease). Most forms of dementia progressively worsen until the person's death.

Some conditions that increase the risk of heart and blood vessel disorders (such as high blood pressure, high levels of cholesterol, and diabetes) seem to increase the risk of dementia.

Depression can cause a type of memory loss (called pseudodementia) that resembles memory loss due to dementia. Also, dementia commonly causes depression. Thus, determining whether dementia or depression is the cause of memory loss can be difficult. However, people with memory loss due to depression, unlike those with dementia, are aware of their memory loss and complain about it. Also, they rarely forget important current events or personal matters, and usually have other symptoms, such as intense sadness, sleeping problems (too little or too much), sluggishness, or loss of appetite.

Stress can interfere with forming a memory and with recalling a memory, partly by preoccupying people and thus preventing them from paying attention to other things. However in certain circumstances, particularly when stress is mild to moderate and does not last long, it can enhance memory.

Less common causes

Many disorders can cause a deterioration of mental function that resembles dementia. Some of these disorders can be reversed with treatment. They include normal-pressure hydrocephalus (due to excess fluid around the brain), subdural hematomas (pockets of blood under the outer layer of the membranes covering the brain), hypothyroidism (an underactive thyroid gland), and vitamin B 12 deficiency.

Other disorders are only partially reversible. They include those that interfere with the supply of blood or nutrients to the brain, such as a cardiac arrest, certain types of stroke, unusually long seizures, head injuries, a brain infection, HIV infection, brain tumors, and overuse of certain drugs (including alcohol). In people with these disorders, treatment can sometimes improve memory and mental function. If damage is more extensive, treatment may not improve mental function but can often prevent further deterioration.

In delirium (see Dementia), memory is affected, but memory loss is not the most noticeable symptom. Rather, people with delirium are very confused, disoriented, and incoherent. Severe alcohol withdrawal (delirium tremens), a severe bloodstream infection (sepsis), lack of oxygen (as may result from pneumonia), and many other disorders can cause delirium, as can use of illegal drugs.

Evaluation

Doctors focus on determining whether the cause is normal age-related changes in the brain, mild cognitive impairment, depression, or early dementia.

Warning signs

In people with memory loss, certain symptoms are cause for concern:

  • Difficulty doing usual daily activities

  • Difficulty paying attention and fluctuations in level of consciousness—symptoms that suggest delirium

  • Depression

When to see a doctor

People with warning signs should see a doctor. They should see a doctor immediately if they

  • Cannot pay attention and seem very confused, unfocused, and disoriented—symptoms that suggest delirium

  • Feel depressed and are thinking of hurting themselves

  • Have other symptoms that suggest a problem with the nervous system, such as headaches, difficulty using or understanding language, sluggishness, vision problems, or dizziness

People who have difficulty doing daily activities should see a doctor within a week or so.

People who do not have warning signs but are concerned about their memory should call their doctor. The doctor can determine how quickly they need to be seen based on other symptoms they have and the severity of the symptoms.

What the doctor does

Doctors ask about the person’s symptoms and medical history. Doctors then do a physical examination. Having a family member present is helpful because people with memory difficulties may not be able to describe their symptoms accurately. What doctors find during the history and physical examination often suggests a cause and the tests that may need to be done (see Table: Some Causes and Features of Memory Loss).

Doctors often talk to the person and the person’s family members separately because family members may not feel free to describe the symptoms candidly with the person listening.

Doctors ask specific questions about the memory loss:

  • What types of things the person forgets (for example, whether the person forgets words or names or gets lost)

  • When the memory problems started

  • Whether memory loss is getting worse

  • How the memory loss is affecting the person’s ability to function at work and at home

Doctors also ask whether the person has other symptoms, such as difficulty using or understanding language and changes in their eating and sleeping habits or mood. They ask about all disorders the person has had and all the drugs the person is taking, including recreational or illegal drugs, to check for possible causes. Information about the person’s education, jobs, and social activities can help doctors better assess the person's previous mental function and gauge the severity of the problem. Doctors ask whether any family members have had dementia or early mild cognitive impairment.

During the physical examination, doctors evaluate all body systems but focus on the nervous system (neurologic examination—see Physical Examination), including evaluation of mental function (mental status testing).

In mental status testing (see Mental status), doctors ask people to answer questions or do specific tasks to evaluate various aspects of mental function, such as

  • Orientation to time, place, and person: State the current date and place and who they are.

  • Attention: Repeat a short list of words.

  • Concentration: Spell "world" backwards or repeat their phone number forward, then backward.

  • Short-term memory: Recall the short list of words after several minutes.

  • Long-term memory: Describe events from the distant past.

  • Use of language: Name common objects and body parts, and read, write, and repeat certain phrases.

This testing also assesses abstract thinking, comprehension, the ability to follow commands and solve math problems, awareness of the illness, and mood.

Some Causes and Features of Memory Loss

Cause

Common Features*

Tests

Age-related memory changes

Occasional forgetfulness of such things as names or the location of car keys

No effect on thinking, other mental functions, or the ability to do daily activities

A doctor's examination (particularly a neurologic examination and mental status testing to assess functions such as attention, orientation, and memory)

Mild cognitive impairment

Memory loss that is more severe than expected for a person's age, particularly difficulty remembering recent events and conversations (short-term memory loss)

No effect on the ability to do daily activities

An increased risk of developing dementia

A doctor's examination

Sometimes formal neuropsychologic testing, which resembles mental status testing but evaluates function in more detail

Dementia

Memory loss that becomes worse as time passes, eventually with no awareness of the loss

Difficulty using and understanding language, doing usual manual tasks, thinking, and planning (for example, planning and shopping for meals), resulting in not being able to function normally

Disorientation (for example, not knowing the time or location)

Changes in personality or behavior (for example, becoming irritable, agitated, paranoid, inflexible, or disruptive)

A doctor’s examination

Usually MRI or CT of the brain

Sometimes formal neuropsychologic testing

Possibly a spinal tap (lumbar puncture) to measure levels of two abnormal proteins (amyloid and tau) that occur in Alzheimer disease

Sometimes blood tests to check for certain causes, such as an underactive thyroid gland (hypothyroidism) or a vitamin deficiency

Depression

Memory loss and awareness of the loss, usually accompanied by intense sadness, and lack of interest in usual pleasures

Sometimes sleep problems (too little or too much), loss of appetite, and slowing of thinking, speech, and general activity

Common among people with dementia, mild cognitive impairment, or age-related changes in memory

A doctor’s examination

Sometimes use of standardized questionnaires to identify depression

Drugs, such as

  • Drugs with anticholinergic effects, including some antidepressants and many antihistamines (used in OTC sleep aids, cold remedies, and allergy drugs)

  • Opioids

  • Drugs that help people sleep (sedatives)

Use of a drug that can cause memory loss

Often recent use of a new drug, an increase in a drug’s dose, or a change in health that prevents the drug from being processed and eliminated from the body normally, as can occur in kidney or liver disorders

Typically stopping the drug to see whether memory improves

*Features include symptoms and results of the doctor's examination. Features mentioned are typical but not always present.

CT = computed tomography; MRI = magnetic resonance imaging; OTC = over-the-counter.

Testing

Doctors can usually determine whether the cause is age-related changes, mild cognitive impairment, or early dementia based on the type of memory loss and the symptoms that accompany it. However, when the diagnosis is unclear, neuropsychologic testing can provide more information. This testing is similar to mental status testing except it is much more detailed. Complete testing may take a full day. These tests must be given by a trained, licensed psychologist or psychiatrist with expertise in memory loss. These tests may not be as useful in people over 65.

If doctors suspect dementia or find any abnormalities during the neurologic examination, they usually do magnetic resonance imaging (MRI) or computed tomography (CT) to check for abnormalities such as a brain tumor, normal-pressure hydrocephalus, damage due to a head injury, and stroke. They may also do blood tests to measure levels of vitamin B 12 and thyroid hormones to determine whether vitamin B 12 deficiency or a thyroid disorder could be causing memory loss. If a brain infection is suspected, doctors usually do a spinal tap (lumbar puncture) to obtain samples of the fluid around the brain (cerebrospinal fluid) for analysis.

Treatment

Treating any disorders contributing to memory loss may help restore memory. For example, vitamin B 12 deficiency is treated with vitamin B 12 supplements, and an underactive thyroid gland is treated with thyroid hormone supplements. For depression, treatment involves drugs, psychotherapy, or both. Doctors choose antidepressants that do not worsen memory loss, such as selective serotonin reuptake inhibitors (SSRIs). For normal-pressure hydrocephalus, a shunt can be surgically placed to drain the excess fluid around the brain. If a person is taking drugs that affect brain function, doctors may stop the drug, decrease the dose, or try substituting another drug.

If the only cause is age-related changes in memory, doctors reassure people that the problem is not serious, that these changes do not mean that mental function will decline substantially, and that there are ways to compensate for losses and possibly to improve mental function (see Memory Loss : Essentials for Older People).

Some generally healthful measures are often recommended:

  • Exercising regularly

  • Eating a healthy diet with lots of fruits and vegetables

  • Getting enough sleep

  • Not smoking

  • Using alcohol only in moderation

  • Participating in social and intellectually stimulating activities

  • Getting regular check-ups

  • Avoiding high levels of stress

  • Protecting the head from injury

These measures, along with controlling blood pressure, cholesterol levels, and blood sugar levels, also tend to reduce the risk of heart and blood vessel disorders. Some evidence suggests that they may reduce the risk of dementia, but this effect has not been proved.

Some experts recommend learning new things (such as a new language or a new musical instrument), doing mental exercises (such as memorizing lists, doing word puzzles, or playing chess, bridge, or other games that use strategy), reading, working on the computer, or doing crafts (such as knitting and quilting). These activities may help maintain or improve mental function, possibly because they strengthen connections between nerves. Having stronger nerve connections helps people postpone the decline in mental function that results from changes in the brain and then helps them compensate for that decline.

Mild cognitive impairment may be treated with donepezil, a drug used to treat Alzheimer disease. This drug may temporarily improve memory, but the benefit appears to be slight. No other drug has been shown to help.

Dementia may be treated with donepezil or certain other cholinesterase inhibitors, such as galantamine and rivastigmine. These drugs may temporarily and slightly improve mental function, including memory, in some people. A different type of drug, memantine, may also help and can be used with a cholinesterase inhibitor. However, no treatment can restore mental function or completely stop the progression of dementia. Thus, treatment focuses on keeping the person safe and providing support as the person declines (see Dementia : Treatment).

If memory loss is relatively severe or family members are concerned about the person's safety, the person's home can be evaluated by occupational or physical therapists. They can recommend ways to prevent falls and other accidents and may suggest protective measures, such as hiding knives, unplugging the stove, and taking the car keys away. Eventually, the person may need a housekeeper or home health aide or may need to move to a one-story home, an assisted-living facility, or a skilled nursing facility.

Essentials for Older People

As people age, most start having some memory problems. Usually, memory loss is caused by normal age-related changes in the brain and does not lead to dementia. Understanding such changes can reduce anxiety and thus help older people adjust and compensate. However, about 14 to 18% of people over 70 have mild cognitive impairment. Dementia occurs in about 1% of people aged 60 to 64 but becomes more likely with increasing age. About 30 to 50% of those over 85 have Alzheimer disease (a type of dementia).

Coping

Strategies that can help people cope with a declining memory include

  • Making lists

  • Keeping a detailed calendar

  • Establishing routines

  • Making associations or relating new information to information already known, such as associating a new person’s name with the name of a movie star

  • Repeating information, such as repeating a new person’s name several times

  • Focusing on (paying attention to) one thing at a time

  • Improving organizational skills, such as keeping frequently used items such as car keys in the same place

Making sure that they can hear and see well can help people stay engaged with others and participate in social activities. Such participation helps people maintain confidence in themselves and often improves mental function.

Key Points

  • Memory loss and fear of dementia are common sources of worry among older people.

  • Usually, memory loss results from normal age-related changes in the brain, which slow mental functions slightly but do not significantly impair them.

  • Memory loss due to dementia usually interferes with the ability to do daily activities and becomes progressively worse.

  • Most people who are aware of memory loss do not have dementia.

  • Doctors can usually identify the cause based on results of the examination, imaging tests (such as MRI or CT), and other tests, including formal tests of mental function.

  • Having a healthy lifestyle, staying mentally active, and participating in social activities may help maintain mental function or postpone its decline.

  • Using lists and other memory aids, focusing on one thing at a time, and getting organized can help older people compensate for age-related changes in memory.

Resources In This Article

Drugs Mentioned In This Article

  • Generic Name
    Select Brand Names
  • RAZADYNE
  • ARICEPT
  • EXELON
  • NAMENDA