What causes memory loss?

Memory loss is one of the most common complaints that bring patients to see a neurologist.

The major classifications are long term memory (that is, memory for events in the remote past, such as from childhood) and short term memory (that is, memory for what was in your breakfast this morning).  The initial evaluation of memory loss by a neurologist involves excluding or "ruling out" reversible causes of memory loss, such as metabolic, endocrine, or infectious disorders.

This is usually achieved with blood tests, but a neuroimaging test (such as a CAT scan or MRI) and/or a spinal tap may also be performed.  Loss of long term memory may be due to acute head injury.  Loss of short term memory is common among the elderly, and in the elderly, when reversible causes are excluded, the most common causes of short term memory loss are on a continuum from least to most severe, from subjective memory loss only, to mild cognitive impairment, to Alzheimer's disease or some other neurodegenerative dementia.  Alzheimer's disease is among the most dreaded diagnoses in neurology, because no interventions slow progression.

Approximately one half of the over 85 population suffers from Alzheimer's disease.  Approved drug therapies are moderately helpful in the earliest stages of the disease, but the drugs always wear off.  There is currently no effective means of delaying, preventing, treating, or reversing Alzheimer's disease, and early stage patients are often referred for clinical trials of new experimental therapies.  The average time from diagnosis to death is 10 years, and during that time, all cognitive function is slowly lost.  Eventually, all Alzheimer's patients take to bed, and death occurs due to an infection such as pneumonia.

There are many causes of memory loss. There are certain vitamin deficiencies that can cause memory problems such as folate and B12 deficiency. Depression can also have coexistant difficulties with memory and can be so severe as to produce a pseudodementia picture. The most common cause of memory loss with other cognitive domains affected such as visuospatial skills, executive planning and calculation difficulties is Alzheimer's dementia. It is normal for all of us to have some challenges to memory and quick retrieval of words as we age but when it goes beyond what is expected of age it may get the label of isolated memory impairment or mild cognitive impairment. A thorough evaluation by a neurologist is essential in looking for different patterns of memory loss in combination with any physical exam findings.
Dr. Michael Roizen, MD
Internal Medicine
In reality, most memory loss is a little like vegetable soup. Your brain is really a pot of several cognitive ailments at once-some neuron loss, some neuron tangling, some vascular problems-that all contribute to losing some ability to recall information. In fact, almost all of us have some of the characteristics as we age. Although science hasn't pinpointed why or how memory loss happens, we do know that chemical changes in the brain's structure hinder the ability to process, store, and retrieve information.

As we get older, everyone has fits of forgetfulness. You might even forget things important to you and seemingly simple to remember, like names of friends, the date of your anniversary, the name of your favorite band (you know, the four guys, c'mon, bad haircuts). Anyway, age-related memory loss is normal. But we don't have to accept normal aging, and we can take steps to prevent age-related memory loss. Memory loss can start as early as age 30, but part of the complication of memory loss associated with aging is that several things cause memory loss. They are:
  • Vascular problems: When insufficient blood gets to the brain, the lack of bloodflow can cause mini-strokes and impair memory.
  • Alzheimer's: Here, neurons tangle with other neurons, causing them to stop working properly.
  • Neuron loss: The loss of neurons or the loss of the function of those neurons causes many age-related problems; literally, you're losing part of your mind.
  • Trauma: Memory loss can also come from trauma sustained during accidents or sports with repetitive injury to the brain, like boxing.
Whatever the official diagnosis, you must remember several important things. One, some memory loss is associated with the loss of non-functioning brain cells, so re-growing functional neurons is important to retain memory skills (we're not sure yet how re-growth can affect those with Alzheimer's). And memory loss is also related to blockages of the small blood vessels, so one of the keys to helping prevent memory loss will be to keep your arteries young.
Majid Fotuhi, MD

Some common causes of memory loss include obstructive sleep apnea, insomnia, medication side effects and mild depression. Watch brain health expert Majid Fotuhi, MD/PhD, discuss these factors and how regular exercise can also help improve memory.


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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.