Forgetfulness or Something More? Normal Ageing Versus Dementia
Everyone forgets things, and after about fifty everyone worries about what the forgetting means. There are reasonably clear distinctions between ordinary age-related change and the pattern that needs assessment.
Normal ageing
With age, processing slows and retrieval takes longer. Typical and not concerning:
- Occasionally forgetting a name and recalling it later
- Walking into a room and forgetting why, then remembering
- Misplacing keys and retracing steps to find them
- Needing a moment longer to learn something new
- Occasionally forgetting an appointment but remembering when reminded
- Being more easily distracted
The key features are that it is occasional, it does not worsen steadily, it does not interfere with independent living, and reminders work.
Warning signs
- Memory loss that disrupts daily life, particularly forgetting recently learned information repeatedly
- Asking the same question several times in a short period and not recalling the answer
- Difficulty with familiar tasks: cooking a routine dish, managing money, following a known route
- Getting lost in familiar places
- Confusion about time or place
- Trouble finding words, substituting wrong words, or losing the thread mid-sentence
- Misplacing things in odd locations, such as a phone in the refrigerator, and being unable to retrace
- Poor judgement, particularly with money, or new susceptibility to scams
- Withdrawal from work, hobbies and social life
- Personality or mood change: suspicion, apathy, irritability
- Reduced attention to hygiene and appearance
The most telling distinction: forgetting part of an event is ordinary. Forgetting the whole event, and not recognising it when reminded, is not.
Another practical one: when the person is unconcerned but the family is worried, that is more significant than when the person is worried and the family is not. Insight tends to be lost as dementia progresses, whereas anxiety about memory is common in depression.
Reversible causes to exclude first
A meaningful proportion of cognitive complaints have a treatable cause. These should be looked for before anything is concluded.
- Depression, which can impair concentration and memory so convincingly it was once called pseudodementia. Very common and very treatable
- Vitamin B12 deficiency
- Hypothyroidism
- Medication side effects. Among the most frequent causes and the most overlooked. Anticholinergics, sedating antihistamines, benzodiazepines, sleeping tablets, some bladder medicines, opioids and certain antidepressants. The cumulative anticholinergic burden of several ordinary medicines can be substantial
- Alcohol
- Obstructive sleep apnoea, which impairs memory and concentration markedly and is treatable
- Chronic poor sleep
- Infection, particularly in older adults where confusion may be the only sign
- Hearing and vision loss. Untreated hearing loss is strongly associated with cognitive decline, and correcting it is one of the clearer modifiable factors
- Normal pressure hydrocephalus, a treatable condition with the triad of gait disturbance, urinary incontinence and cognitive decline
- Subdural haematoma, sometimes after a minor fall that was forgotten
- Delirium, an acute confusional state with fluctuating attention, which is a different condition from dementia and usually has an identifiable medical cause
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What assessment involves
- A detailed history, ideally with someone who knows the person well, because self-report is unreliable in both directions
- Cognitive testing such as MMSE, MoCA or ACE, which measure several domains rather than memory alone
- Blood tests: full blood count, glucose or HbA1c, kidney and liver function, thyroid, B12, folate, calcium, and sometimes syphilis and HIV serology
- Brain imaging, CT or MRI, to look for stroke, tumour, hydrocephalus and patterns of atrophy
- Specialist referral for unclear cases, early-onset presentations, or rapid progression
Mild cognitive impairment
An intermediate state: measurable cognitive decline beyond normal ageing, but daily function is preserved. Some people progress to dementia, some remain stable, and some improve, particularly where a reversible contributor is found and treated.
An MCI diagnosis is therefore a reason to act on modifiable factors, not a sentence.
The main types of dementia
Alzheimer disease, the commonest. Gradual onset, memory for recent events affected first, slow steady progression.
Vascular dementia, from cumulative small strokes or chronic small vessel disease. Often stepwise rather than smooth decline, with prominent slowing and executive difficulty. Risk factor control genuinely matters here.
Lewy body dementia. Fluctuating alertness, detailed visual hallucinations, parkinsonian features, and acting out dreams during sleep. Importantly, people with this type can react severely to certain antipsychotic medicines, which is why the diagnosis matters.
Frontotemporal dementia. Often younger onset, with personality change, loss of social restraint or language difficulty, and memory relatively preserved early.
Mixed pathology is common, particularly Alzheimer plus vascular.
Why early assessment is worth it
Even without a cure, earlier is better:
- Reversible causes can be found and treated
- Medicines can modestly help symptoms, and newer disease-modifying treatments for Alzheimer disease are only appropriate in early disease
- Vascular risk factor control slows vascular contribution
- Legal and financial planning, including power of attorney, is possible while the person has capacity
- Driving, medication safety and home safety can be managed before an incident
- Families can access support rather than coping alone
- Depression and sleep apnoea, if found, are treatable in their own right
Reducing risk
The evidence points consistently to a set of modifiable factors across life: treating hearing loss, controlling blood pressure, treating diabetes, not smoking, limiting alcohol, treating depression, staying physically active, remaining socially connected, protecting the head from injury, addressing obesity, and air quality.
None of these guarantees anything. Collectively they are associated with a meaningful share of dementia risk.
The short version
Forgetting part of a conversation is ordinary; forgetting the conversation happened is not. Before accepting any conclusion, make sure depression, B12, thyroid, sleep apnoea, hearing loss and the person’s full medication list have been reviewed, because several of those produce convincing memory problems and all of them are treatable.