Dementia is a syndrome caused by diseases and injuries that affect the brain. It can affect memory, thinking, language, judgement, behaviour and the ability to manage everyday activities. Although dementia becomes more common with age, it is not an inevitable part of normal ageing.

Possible early signs

• Increasing difficulty remembering recent events or conversations.
• Repeated questions, misplaced objects or difficulty keeping track of appointments.
• Getting lost or becoming confused in familiar places.
• Difficulty planning, solving problems or managing money and medicines.
• Problems finding words, following conversations or understanding information.
• Difficulty carrying out previously familiar tasks.
• Changes in judgement, motivation, personality, mood or social behaviour.

How dementia is assessed

Assessment generally starts with a detailed history from the person and, where appropriate, someone who knows them well. Depending on the presentation, clinicians may assess cognition and function, review medicines and physical health, perform relevant examinations and tests, and consider brain imaging or specialist neuropsychological assessment when it would help clarify the diagnosis or subtype.

Common causes

Alzheimer disease is the most common cause of dementia. Other causes include vascular dementia, dementia with Lewy bodies, frontotemporal dementia and mixed forms. Management differs between subtypes, so identifying the most likely cause can be clinically important.

Treatment and support

There is no single treatment suitable for every form of dementia. Care may include treatment of contributing medical conditions, review of medicines, cognitive and functional support, management of mood or behavioural symptoms, family and caregiver education, safety planning, rehabilitation and advance planning. Some medicines can help symptoms in selected dementia subtypes and should be chosen after specialist assessment.

Changes in behaviour, agitation or psychosis

When distress, agitation, hallucinations or aggression occur, the first step is to look for possible causes such as pain, infection, delirium, medicine effects, environmental stress or unmet needs. Psychosocial and environmental approaches are generally preferred first. Antipsychotic medicines may sometimes be required when there is significant risk of harm or severe distress, but they require careful clinical assessment and monitoring.

When urgent assessment is needed

• Sudden onset or rapid fluctuation of confusion or drowsiness.
• New weakness, facial droop, speech difficulty or other possible stroke symptoms.
• Severe agitation, aggression or inability to maintain basic safety.
• Suicidal thoughts or behaviour.
• Fever, dehydration, suspected infection, overdose or another medical emergency.

Support for families and caregivers

Dementia affects families as well as the person living with the condition. Caregiver education, realistic routines, communication strategies, respite, safety planning and support for caregiver stress can be important parts of long-term care.

Clinical sources

World Health Organization: Dementia (3 July 2026)
NICE NG97: Dementia — assessment, management and support

This information is for general education and does not replace an individual assessment or professional medical advice.