What Causes Forgetfulness? When Can Memory Problems Be a Sign of Disease?

Forgetfulness can occur in everyone from time to time. A busy schedule, insufficient sleep, stress or reduced attention can make it temporarily difficult to remember names, appointments or where an item has been placed.

Not every memory lapse means Alzheimer's disease or dementia. Medical assessment becomes more important when memory problems progressively worsen or begin to interfere with work, household tasks, medication management, finances, navigation or other everyday activities.

Memory problems can be associated with many conditions other than neurodegenerative disease, including depression, anxiety, sleep disorders, certain medicines, nutritional deficiencies, thyroid disorders, metabolic problems, sensory impairment and cerebrovascular disease.

What Is Forgetfulness?

Memory involves learning information, storing it and retrieving it when needed. Memory performance also depends on attention, sleep, mood, language, executive function and adequate sensory input.

For this reason, a person who feels that their memory is failing may actually be experiencing difficulty related to:

• Reduced attention
• Poor concentration
• Insufficient sleep
• Depression or anxiety
• Severe or prolonged stress

What Is Normal Age-Related Forgetfulness?

As people become older, learning new information or retrieving a memory can sometimes take longer. This alone does not indicate dementia.

Examples that can occur with normal ageing include:

• Temporarily forgetting someone's name but remembering it later
• Occasionally misplacing a phone or keys
• Occasionally forgetting an appointment and remembering it later
• Taking longer to learn new technology or a new procedure

People experiencing normal age-related changes generally remain independent in their everyday activities.

What Is Mild Cognitive Impairment?

Mild cognitive impairment (MCI) describes memory or other thinking problems that are greater than expected for a person's age while everyday independence remains largely preserved.

Possible signs include:

• Losing things more frequently
• Forgetting appointments or planned events more often
• Greater difficulty finding words than other people of a similar age
• Family or friends beginning to notice cognitive changes

Not everyone with MCI develops dementia. Symptoms may remain stable and in some cases can improve, particularly when an underlying treatable contributor is identified.

What Is the Difference Between Forgetfulness and Dementia?

Dementia is not simply forgetfulness. It describes deterioration in memory, thinking, language, judgement, problem-solving, behaviour or other cognitive abilities that becomes severe enough to interfere with everyday functioning.

Dementia is not an inevitable part of normal ageing.

Early changes may include:

• Frequently forgetting recent events
• Repeatedly asking the same questions
• Becoming lost in familiar places
• Difficulty managing finances or bills
• Marked difficulty finding words
• Difficulty planning or making decisions
• Difficulty completing familiar tasks
• Changes in personality or behaviour

According to the World Health Organization's 2026 update, Alzheimer's disease is the most common cause of dementia and may contribute to approximately 60–70% of cases.

Other important causes include vascular dementia, dementia with Lewy bodies, frontotemporal dementia, Parkinson's disease dementia and mixed forms of dementia.

What Else Can Cause Forgetfulness?

Memory complaints have many possible causes, some of which are treatable.

Depression and Anxiety

Depression, persistent anxiety and severe stress can interfere with attention and concentration. If information is not effectively registered in the first place, it becomes more difficult to retrieve later.

Sleep Problems

Insufficient sleep, poor-quality sleep and conditions such as obstructive sleep apnoea may affect daytime attention and cognitive performance.

Nutritional and Metabolic Problems

Vitamin B12 deficiency, thyroid dysfunction and certain metabolic abnormalities may contribute to cognitive symptoms.

Vascular Disease

Stroke, cerebral small-vessel disease and other cerebrovascular conditions can affect memory, processing speed and executive function.

Neurological Conditions

Head injury, some brain tumours, neurodegenerative disorders, epilepsy and selected infectious or autoimmune neurological diseases can cause cognitive change.

Hearing and Vision Loss

Significant hearing or visual impairment can reduce the amount and quality of information a person receives from their surroundings and may make cognitive performance appear worse than it is.

Can Medicines Cause Memory Problems?

Yes. Certain medicines can affect attention, memory or alertness, particularly in older adults.

Possible contributors include:

• Medicines with significant anticholinergic effects
• Some sleeping tablets and sedatives
• Some strong pain medicines
• The combined effects of multiple medicines

A review of all prescription medicines, over-the-counter products and supplements is therefore an important part of cognitive assessment.

When Should You See a Doctor About Forgetfulness?

Medical assessment is appropriate when:

• Memory problems are progressively worsening
• The person repeatedly asks the same questions
• They become lost in familiar places
• They struggle to take medicines correctly
• Managing bills, banking or money becomes difficult
• Previously familiar tasks become difficult
• Speech or word-finding abilities change noticeably
• Judgement or decision-making deteriorates
• Personality or behaviour changes
• Family members or friends notice a significant cognitive change

Which Memory or Mental-State Changes Require Urgent Assessment?

Slowly progressive memory problems over months or years are different from sudden confusion developing over hours or days.

Urgent medical assessment may be required for:

• Sudden marked confusion or altered consciousness
• New speech difficulty
• Facial drooping
• Sudden weakness or numbness in an arm or leg
• Sudden visual loss or severe balance problems
• A new seizure
• Memory or consciousness changes after a head injury
• A severe new headache with altered mental state
• Marked confusion associated with fever

How Are Memory Problems Assessed?

There is no single test that explains every case of forgetfulness. Assessment is performed step by step according to the person's symptoms and circumstances.

Medical History

Assessment may explore:

• When the problems began
• Whether they are worsening
• Their effect on everyday functioning
• Sleep and mood
• Medication use
• Alcohol and other substances
• Previous stroke or head injury
• Relevant family history

Information from someone who knows the person well can be particularly valuable.

Physical and Neurological Examination

Strength, walking, balance, reflexes, speech and other neurological functions may be assessed. Mood, hearing and vision may also require evaluation.

Cognitive Assessment

Brief validated cognitive tests can assess areas including memory, attention, orientation, language, planning, executive function and visuospatial skills.

A normal score on one brief cognitive test should not, by itself, rule out cognitive disease when clinical concern remains significant.

Which Tests May Be Used for Forgetfulness?

Everyone does not require the same test panel. Investigations should be guided by the clinical assessment.

Blood Tests

Depending on the circumstances, investigations may include:

• Full blood count
• Vitamin B12
• Thyroid function
• Glucose
• Electrolytes
• Liver and kidney function

Testing for infection, autoimmune disease or other less common causes is selected when the clinical history indicates a reason to investigate them.

Brain MRI or CT

Structural brain imaging can help assess for stroke, tumours, hydrocephalus, vascular disease, characteristic patterns of atrophy and other structural abnormalities.

MRI usually provides more detailed assessment of brain tissue, while CT may be used depending on urgency, availability, contraindications and the clinical question.

Neuropsychological Testing

More detailed neuropsychological testing may be useful when it remains unclear whether cognitive impairment is present, whether it represents dementia or which subtype is most likely.

Testing can examine memory, attention, language, processing speed, executive function and visuospatial abilities in detail.

Is EEG Necessary for Forgetfulness?

EEG is not routinely required for every person with memory problems.

Electroencephalography may be useful when there is concern about:

• Epileptic seizures
• Recurrent episodes of altered awareness
• Certain encephalopathies
• Unusually rapid or atypical cognitive decline

EEG is not a routine diagnostic test for Alzheimer's disease.

How Is Forgetfulness Treated?

There is no single treatment for forgetfulness. Treatment is directed at the underlying cause.

For example, cognitive symptoms may improve when:

• Vitamin B12 deficiency is corrected
• Thyroid disease is appropriately treated
• Depression or anxiety is treated
• Sleep apnoea or another sleep disorder is managed
• Medicines that affect cognition are reviewed
• Significant hearing or visual impairment is addressed

Mild Cognitive Impairment

There is no single standard medicine that treats all causes of MCI. Underlying risk factors should be addressed and cognition monitored over time.

Dementia

When dementia is diagnosed, treatment depends on the cause and stage.

Medicines such as donepezil, rivastigmine, galantamine or memantine may be appropriate for selected patients with Alzheimer's disease or certain other dementia syndromes. Medication choice differs between dementia types.

Physical activity, rehabilitation, cognitive stimulation, social engagement, environmental adaptations and support for family carers are also important components of care.

How Can Cognitive Health Be Supported?

There is no single intervention that can prevent every type of dementia. Current WHO guidance nevertheless identifies several modifiable factors that can help reduce the risk of cognitive decline and dementia.

Helpful measures include:

• Remaining physically active
• Not smoking
• Avoiding harmful alcohol use
• Following a healthy, balanced diet
• Managing blood pressure
• Managing diabetes and cholesterol
• Maintaining a healthy body weight
• Remaining socially engaged
• Continuing cognitively stimulating activities
• Addressing hearing loss when present
• Assessing significant sleep problems

Frequently Asked Questions

References

1. Academic Hospital. Forgetfulness: Which Situations Can Be a Harbinger of Disease?
2. World Health Organization. Dementia – Fact Sheet
3. National Institute on Aging. Memory Problems, Forgetfulness, and Aging
4. National Institute on Aging. What Is Mild Cognitive Impairment?
5. National Institute for Health and Care Excellence (NICE). Dementia: Assessment, Management and Support for People Living With Dementia and Their Carers
6. World Health Organization. Risk Reduction of Cognitive Decline and Dementia: WHO Guidelines, Second Edition