Alzheimer's Disease

What Alzheimer's Disease is

Alzheimer's Disease is a neurodegenerative condition characterised by the accumulation of two abnormal proteins in the brain: amyloid-beta plaques (between neurons) and tau tangles (inside neurons). These changes start years to decades before symptoms appear, initially in the medial temporal lobes (where the hippocampus formation lies, central to memory), and spread to other cortical regions as the disease progresses. The result is a gradual loss of brain cells and a progressive impairment of cognition and, eventually, daily function.

Around one in every 14 people over 65, and one in six over 80, has Alzheimer's Disease. It is more common in women than men, in part because women on average live longer, and is more common in people with a family history of the disease, in those with the APOE4 gene variant, and in people with significant uncontrolled vascular risk factors.

The ICD-11 codes

UK memory clinics, including The Dementia Service and most NHS services, code Alzheimer's Disease in line with the World Health Organization's eleventh revision of the International Classification of Diseases (ICD-11):

• 6D80 Dementia due to Alzheimer's Disease (parent code).
• 6D80.0 Early-onset Alzheimer's Disease (symptoms before age 65).
• 6D80.1 Late-onset Alzheimer's Disease (symptoms from age 65 onward), by far the most common.
• 6D80.2 Mixed Alzheimer's and Vascular Dementia.
• 6D80.3 Alzheimer's Dementia, mixed type, with other non-vascular aetiologies.

Symptoms by stage

Pre-symptomatic and prodromal stages

Alzheimer's Pathology may be present for many years before any symptoms emerge. The first clinical phase is often described as Mild Cognitive Impairment due to Alzheimer's Disease, in which short-term memory and word-finding are measurably affected but everyday independence is preserved. See our MCI page.

Mild Alzheimer's Dementia

Forgetting recent conversations and events, repeating questions, misplacing things, struggling with names, mild navigation errors, mild word-finding pauses, modest difficulty with complex tasks (managing finances, planning trips). Many people in this stage continue to live independently with light family support.

Moderate Alzheimer's Dementia

Greater need for assistance with day-to-day tasks: reminders for medication, support with shopping and cooking, supervision around the home for safety. Disorientation in unfamiliar places becomes more common; orientation in time may also slip. Mood changes, irritability and apathy are common. Behavioural and psychological symptoms (anxiety, restlessness, sleep disturbance) often emerge here.

Severe Alzheimer's Dementia

Substantial support is needed for most activities of daily living, including personal care, eating and continence. Communication becomes more limited, sometimes restricted to single words or phrases. Mobility declines. Care needs typically increase, with many people requiring residential care at this stage.

How Alzheimer's is diagnosed

UK memory clinics follow NICE NG97. A robust diagnostic process includes:

• A detailed history, ideally with input from a close family member;
• A structured cognitive test such as the ACE-III;
• Routine blood tests to rule out reversible causes (thyroid, B12, folate, vitamin D, calcium, glucose, liver and kidney function);
• An ECG, especially if cholinesterase inhibitors are being considered;
• A structural MRI (preferred) or CT brain scan;
• Where uncertainty remains, advanced imaging (FDG-PET) or Lumbar Puncture for CSF biomarkers.

NICE NG97 explicitly states that Alzheimer's should not be ruled out on imaging alone. The typical MRI finding is medial temporal atrophy on the Scheltens Scale; in our cohort the mean MTA grade in clinically diagnosed Alzheimer's was 1.79, with around one in six showing an unremarkable scan.

Current UK treatments

Cholinesterase inhibitors and Memantine

NICE Technology Appraisal TA217 recommends Donepezil, Galantamine and Rivastigmine for mild to moderate Alzheimer's, and Memantine for moderate to severe disease (or where the cholinesterase inhibitors are not tolerated). Around 60 per cent of people who tolerate these medicines experience a measurable improvement in attention, memory and the ability to carry on day-to-day life. See cholinesterase inhibitors and Memantine.

Disease-modifying therapies (Lecanemab, Donanemab)

These intravenous antibodies remove amyloid plaques and have shown a modest slowing of decline in clinical trials in early Alzheimer's. NICE's June 2025 appraisals recommended against routine NHS use of both medicines on cost-effectiveness grounds; the position may change. See our Lecanemab and Donanemab page.

Non-pharmacological treatments

Cognitive Stimulation Therapy, Reminiscence Therapy, music and art-based interventions, structured routines, regular exercise and a Mediterranean-style diet all have evidence supporting their use in Alzheimer's. None is a cure, but together they make a meaningful difference to quality of life.

Vascular risk reduction

Controlling blood pressure, cholesterol, glucose, smoking and alcohol slows progression in pure Alzheimer's as well as mixed dementia. See vascular risk reduction.

What course the disease takes

Average life expectancy from clinical diagnosis is around 8 to 10 years, but the range is wide. Some people remain in the mild stage for many years; others progress faster. Factors associated with faster progression include older age at diagnosis, more advanced disease at presentation, untreated vascular risk factors, frequent Delirium, untreated mood disorder and social isolation. Factors associated with slower progression include early diagnosis, treatment adherence, good cardiovascular health, regular physical and cognitive activity, social engagement and good carer support.

Living well with Alzheimer's

A diagnosis of Alzheimer's is the start of a long road that, with the right support, can be navigated well. Practical priorities in the first year include:

• Putting Lasting Power of Attorney in place for both health and finance while capacity is intact;
• Reviewing driving with the DVLA;
• Setting up the routines, prompts and assistive technology that support independence;
• Connecting with the Alzheimer's Society and a local memory cafe;
• Carer education and a plan for support that grows as needs grow.

Where to get assessed in the UK

NHS memory clinics provide diagnostic assessment for most people; waiting times vary by region. If you would prefer to be seen quickly, would value an ICD-11 aligned letter and a clear plan for onward investigation, The Dementia Service is the leading UK private memory clinic, with virtual assessment, structured reporting and shared-care prescribing with your GP. The two routes are not mutually exclusive; many people use both.