Dementia — Types, Causes, Diagnosis, Donepezil & Management Guide — Symptoms, Causes & Treatment | MyMedicPlus

Dementia is an umbrella term for a group of conditions characterised by progressive decline in multiple cognitive domains — including memory, language, executive function, attention, visuospatial skills, and personality — severe enough to impair daily functioning and independent living. Dementia is not a normal part of ageing. The most common types: Alzheimer's disease (AD — 60-70% of cases, characterised by amyloid plaques and neurofibrillary tau tangles); vascular dementia (VaD — 15-20%, caused by cerebrovascular disease — stroke and small vessel disease); Lewy body dementia (LBD — 10-15%, characterised by alpha-synuclein Lewy body inclusions, visual hallucinations, parkinsonism, and REM sleep behaviour disorder); frontotemporal dementia (FTD — 5-10%, earlier onset, prominent personality change and executive dysfunction); mixed dementia (AD + VaD — common in the elderly).

Alzheimer's disease: caused by accumulation of amyloid beta (Abeta) plaques in the brain and neurofibrillary tau tangles, leading to neuronal death. Risk factors: age (most important — risk doubles every 5 years after 65); female sex (higher lifetime risk, partly due to longer life expectancy); APOE e4 allele (most common genetic risk factor — heterozygous 2-3x risk; homozygous 8-12x risk); Down syndrome (trisomy 21 — nearly all develop AD pathology by age 40-50 due to extra APP gene copy); family history of early-onset AD (mutations in APP, PSEN1, PSEN2 genes — autosomal dominant; account for less than 1% of all AD). Modifiable risk factors for dementia (Lancet 2024 Commission — 45% of dementia attributable): low education, hypertension (midlife), hearing loss, smoking, obesity, depression, physical inactivity, diabetes, low social contact, excess alcohol, traumatic brain injury, air pollution, high LDL cholesterol, and untreated vision loss.

Early Alzheimer's disease: short-term memory loss (forgetting recent conversations, appointments, names); getting lost in familiar places; word-finding difficulties (anomia); difficulty with complex tasks (managing finances, planning); and personality/mood changes (anxiety, depression, withdrawal). Moderate AD: significant memory loss; disorientation to time and place; agitation, wandering, and sundowning (worsening confusion in the evening); assistance required for bathing, dressing, and toileting. Severe AD: inability to recognise family members; incontinence; limited verbal communication; loss of mobility; and swallowing difficulties. Lewy body dementia: detailed visual hallucinations (often elaborate — people or animals, well-formed); parkinsonism (tremor, rigidity, bradykinesia); fluctuating cognition; REM sleep behaviour disorder (acting out dreams — often precedes cognitive decline by years). Vascular dementia: stepwise decline (sudden worsening after each stroke or TIA); focal neurological deficits; prominent executive dysfunction; gait disturbance.

Clinical history from patient and carer: onset, progression, pattern of cognitive and functional decline; medication review (drugs causing cognitive side effects). Cognitive assessment: MMSE (Mini-Mental State Examination), MoCA (Montreal Cognitive Assessment, more sensitive for mild dementia), ACE-III (Addenbrooke's Cognitive Examination — comprehensive). Brain imaging: MRI brain (standard — assesses for hippocampal atrophy in AD, cerebrovascular disease in VaD, structural causes — tumour, normal pressure hydrocephalus, subdural haematoma); CT brain if MRI contraindicated. Blood tests: exclude reversible causes — thyroid function (hypothyroidism causes cognitive impairment), B12 and folate, FBC, renal function, liver function, calcium, glucose, syphilis serology (VDRL), and HIV in appropriate populations. CSF biomarkers: amyloid-42, phosphorylated tau, and total tau — used in specialist settings to support AD diagnosis; CSF Abeta42/40 ratio reduced and ptau181 elevated in AD. Amyloid PET scan: detects amyloid plaque deposition in living brain — used in clinical trials and increasingly in specialist dementia clinics for early/atypical AD. Genetic testing: APOE genotyping and familial AD gene panel for appropriate patients.

Cholinesterase inhibitors (for Alzheimer's disease): donepezil (Aricept — most commonly prescribed; 5 mg for 1 month then 10 mg daily); rivastigmine (Exelon — also approved for Parkinson's disease dementia; available as 9.5 mg/24hr transdermal patch); galantamine (Reminyl). These drugs inhibit acetylcholinesterase — increasing acetylcholine availability in the brain. They modestly slow cognitive and functional decline in mild-moderate AD; do not prevent or reverse neurodegeneration. Memantine (Ebixa): NMDA receptor antagonist; approved for moderate-severe AD; can be used alone or with donepezil; modest benefit on cognition, behaviour, and daily function. New disease-modifying therapy (anti-amyloid antibodies): lecanemab (Leqembi — anti-amyloid antibody) — Phase III trial (CLARITY AD) showed 27% slowing of clinical decline at 18 months in early AD; approved by FDA (2023) and NICE (2025) for early AD (MCI/mild dementia with confirmed amyloid pathology); given IV every 2 weeks; risk of ARIA (amyloid-related imaging abnormalities — brain microbleeds/oedema — 21% incidence); donanemab (Kisunla) — similar efficacy, approved FDA 2024. Non-pharmacological interventions: cognitive stimulation therapy (CST); cognitive rehabilitation; structured exercise (reduces rate of decline); reminiscence therapy; social engagement; carer support and education; dementia care coordinators; music therapy and life story work for behavioural symptoms. Managing BPSD (behavioural and psychological symptoms — agitation, psychosis, depression): person-centred care approaches first; antipsychotics (risperidone) only for severe/dangerous symptoms and short-term (increased stroke and mortality risk in dementia).

Dementia is progressive and ultimately fatal — most patients die from complications of severe dementia rather than the dementia itself. Aspiration pneumonia (most common cause of death — from swallowing difficulties and impaired cough reflex in severe dementia). Falls and hip fractures — impaired gait, balance, and spatial awareness; falls are the leading cause of hospitalisation in dementia. Urinary tract infections from incontinence and catheter use. Malnutrition and dehydration in severe stages. Delirium (acute-on-chronic confusion) precipitated by any acute illness, medication, or hospitalisation — causes accelerated cognitive decline. Behavioural and psychological symptoms of dementia (BPSD): agitation, aggression, wandering, sleep disturbance, paranoid delusions — a major cause of carer stress and the leading reason for nursing home placement. Social isolation and depression are common in early stages. Caregiver burnout is a critical consideration — caregivers of people with dementia have significantly higher rates of depression and anxiety than age-matched controls.

The Lancet 2024 Dementia Prevention Commission identified 14 modifiable risk factors accounting for approximately 45% of dementia cases. Lifestyle modifications with strongest evidence: physical activity (150 minutes/week of moderate aerobic exercise reduces dementia risk by 35%); treat hypertension (especially midlife BP — SPRINT-MIND trial); address hearing loss (hearing aids reduce dementia risk); quit smoking; treat depression; maintain social connection and cognitive engagement; achieve and maintain a healthy weight; control diabetes; limit alcohol; address vision loss; prevent head injury. Cognitive reserve: higher educational and occupational attainment, bilingualism, cognitively stimulating leisure activities, and social engagement build brain resilience. Mediterranean diet and MIND diet (Mediterranean-DASH Intervention for Neurodegenerative Delay): emphasising leafy greens, berries, nuts, olive oil, fish — associated with 35-53% reduced dementia risk. Treating cardiovascular risk factors (hypertension, hyperlipidaemia, diabetes) remains the most impactful evidence-based dementia prevention strategy.

See a GP promptly if you or a family member notices: persistent memory problems affecting daily life (forgetting recent events, repeated questioning, difficulty with familiar tasks); getting lost in familiar places; significant personality or behaviour changes; language difficulties (word-finding problems, incoherent speech); difficulties managing finances, medications, or complex tasks; or a sudden, rapid deterioration in cognition (which may indicate delirium from an acute illness, or a reversible cause such as hypothyroidism, B12 deficiency, or medication side effects). Early diagnosis enables access to cholinesterase inhibitor treatment, safety planning, carer support, legal and financial planning, and in eligible patients, emerging disease-modifying therapy (lecanemab). Do not accept memory problems as 'just normal ageing' without assessment.