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While some decline in the ability to remember is a normal part of aging, for a subset of people, growing older brings the onset of neurodegenerative conditions such as Alzheimer’s disease. In such cases, dementia gradually grows more severe and memory worsens to a much greater extent than is typical in the general population.

Amnesia, or abnormal memory loss, can also result from a range of other medical conditions, sudden brain injury, substance use, or in reaction to a traumatic event.

Dementia and Memory Loss

Dementia is a progressive loss of cognitive function, most commonly caused by Alzheimer's disease but also by a number of other conditions. Memory loss is a major part of this functional decline, typically emerging as a mild impairment and growing more severe as dementia worsens. An estimated 50 million people worldwide have some form of dementia.

How does dementia affect memory?

Dementia involves damage to parts of the brain that are important for memory, including the hippocampus and the frontal lobes. Consequently, memory problems are among the core symptoms of dementia. People with dementia may quickly forget personal experiences, frequently repeat themselves, experience distorted memories, not recognize family members, or get lost in a place they once knew well, along with other forms of memory breakdown. Forgetting may seem to move backward in time, beginning with recent events and ultimately affecting memories from many years earlier.

How severe is memory loss in dementia?

Someone with dementia progresses through stages of severity, and problems with forgetting grow worse over time. Relatively mild memory symptoms may include not remembering that one completed a task or recently told someone something. But dementia can ultimately involve severe memory problems such as being unable to retain new information or recognize loved ones. 

Types of Amnesia

Amnesia is a substantial loss of memory, including diminished ability to remember the past, to create new memories, or both. Amnesia can have many possible causes and encompasses various manifestations of memory loss, including sudden and temporary forms as well as gradual and permanent losses, as in dementia.

What are retrograde amnesia and anterograde amnesia?

Amnesia can include problems with both the retrieval of previously formed memories and the formation of new ones. Retrograde amnesia is a difficulty with remembering information acquired in the past, including facts and the details of personal experiences. Anterograde amnesia is a difficulty with storing new information in memory. A person may experience both kinds of amnesia, or one kind without the other.

What is transient global amnesia?

Transient global amnesia involves a temporary inability to retain new memories, even as one remembers details from the past (including who one is and who others are). It may also impede the ability to recall recent memories. It is a rare syndrome that is most likely to effect individuals over age 50. Those who experience it typically return to normal memory function within a day, often in as little as a few hours.

Assessing Memory

When a concerning or hard-to-explain loss of memory becomes apparent to an individual or to the person's friends or family, it’s best to consult a health care provider. A neurological assessment alongside a professional examination of one’s memory can help determine whether increased forgetfulness is a symptom of an underlying condition and if any intervention is warranted.

When should I get my memory tested?

Some degree of memory loss is a normal part of aging, but amnesia can be a sign of serious medical problems. A medical professional should be consulted if a person shows warning signs such as failing to remember information that is used frequently, struggling to complete tasks due to memory challenges, or otherwise exhibiting a noticeable and unexplained increase in forgetfulness.

How do clinicians diagnose a memory disorder?

An assessment for potential memory problems may involve a basic screening of one’s ability to recall information, possibly followed by a more formal, in-depth neuropsychological evaluation to analyze memory and other cognitive functions. A health care provider may also investigate potential factors in memory problems using neuroimaging, lab tests for relevant vitamins and hormones, and an examination of the role any medications might play.

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