Synopsis
Distinguish mild cognitive impairment from dementia and delirium using collateral functional evidence, adapt cognitive testing to language and sensory needs, identify reversible contributors, and reach a defensible subtype through specialist assessment and imaging.
- Dementia is acquired progressive cognitive decline severe enough to interfere with independent everyday function; mild cognitive impairment causes objective decline while basic independence is substantially retained.
- MCI is a risk state, not inevitably early Alzheimer disease: some people progress, some remain stable and some improve when sleep, mood, medicines, sensory loss or illness is addressed.
- The most diagnostic information is often the change from the person’s previous abilities—money, medication, travel, cooking, technology, work and judgement—not one cross-sectional memory score.
- Obtain collateral history with consent and create a timeline of onset, progression, stepwise change, fluctuation, neurological symptoms, behaviour and daily function.
- Exclude delirium first and assess depression, anxiety, alcohol, sleep apnoea, pain, hearing, vision, endocrine disease and anticholinergic or sedative medicines as contributors.
- Use a validated brief cognitive instrument such as 6CIT, Mini-Cog, 10-CS or GPCOG, but do not rule out dementia solely because a score is normal.
- Interpret testing through education, first language, literacy, culture, hearing, vision, motor and communication ability; choose an adapted tool or specialist assessment when necessary.
- Initial blood tests commonly include full blood count, renal, liver, thyroid, calcium, glucose or HbA1c, vitamin B12 and folate, with infection tests selected from risk and presentation.
- Structural CT or MRI helps exclude important pathology and support subtype, but atrophy or white-matter change cannot replace clinical functional diagnosis.
- Assess driving, medication safety, falls, nutrition, fire, finances, vulnerability, capacity and carer strain from the first evaluation while avoiding blanket assumptions of incapacity.
Key red flags
Hours-to-days onset, fluctuation, impaired attention and altered arousal in an acutely ill person indicates delirium even when chronic neurodegeneration increases vulnerability.
Presentation before 65, rapid progression, seizures, neurological signs, early language or behavioural syndrome or strong family history warrants expedited specialist and sometimes tertiary assessment.
Investigation priorities
Establish decline from baseline, functional consequences and the pattern that suggests a subtype.
Management branches
The person or someone close reports new memory or thinking difficulty.
- 1. Establish hours, weeks or years of change and screen attention, arousal, observations, acute illness, medication change and focal neurology before cognitive scoring.
- 2. If delirium is possible, investigate and treat causes urgently while documenting the pre-illness cognitive baseline from collateral history.
- 3. For progressive concerns, obtain patient and consented informant examples across cognition, behaviour and instrumental daily activities.
- 4. Assess mood, sleep, alcohol, hearing, vision and medication burden and agree immediate safety measures without waiting for a final subtype.
Key medicines
Deprescribing cognitive-burden medicinesReview anticholinergic, sedative, opioid and other contributing medicines one at a time; taper gradually where withdrawal is possible and use current drug-specific and local deprescribing guidance.Do not abruptly stop benzodiazepines, gabapentinoids, antidepressants or necessary psychiatric treatment. Balance recurrence of the treated condition, involve the original prescriber and monitor after each change.
No routine cognitive enhancer for isolated MCIDo not start donepezil, another cholinesterase inhibitor or memantine solely for an undifferentiated MCI label; treatment requires an indicated dementia subtype and specialist-informed plan.MCI can represent early neurodegeneration, so absence of medication is not absence of care. Arrange risk-factor work, support and longitudinal reassessment, and use biomarkers only through appropriate services.