Dementia: Assessment and Diagnosis

Introduction

Dementia is an umbrella term for an acquired, progressive decline in cognitive function - typically involving memory, but also language, executive function, visuospatial skills or personality - occurring in clear consciousness and severe enough to interfere with a person's usual daily activities. It is caused by several distinct underlying diseases (Alzheimer's disease, vascular dementia, Lewy body dementia, frontotemporal dementia and others, each covered separately), but shares a common approach to initial recognition, assessment and diagnosis, which is the focus of this article.¹

Around 900,000 people are estimated to be living with dementia in the UK, a figure projected to rise substantially as the population ages, making its recognition and management a core skill across almost every specialty, not just geriatric medicine.

Distinguishing dementia from normal ageing and delirium

Some decline in processing speed and occasional word-finding difficulty is a normal part of ageing and does not, by itself, indicate dementia. What distinguishes dementia is progressive impairment that affects function - difficulty managing finances, medications, or familiar tasks that were previously straightforward.

Delirium - covered in detail in ² - is acute and fluctuating, in contrast to the gradual, progressive course of dementia, though the two frequently coexist, and an episode of delirium can unmask previously unrecognised or compensated-for dementia. Establishing a clear timeline via collateral history is the key tool for telling them apart.

Presentation

• Memory: repeating questions, forgetting recent conversations or appointments, misplacing items
• Language: word-finding difficulty, reduced vocabulary, difficulty following conversation
• Executive function: difficulty planning, organising, or managing multi-step tasks (finances, medication, cooking)
• Visuospatial: getting lost in familiar places, difficulty judging distances
• Behaviour and personality: apathy, disinhibition, irritability, or withdrawal from usual activities and social contact
• Insight: often reduced, meaning a collateral history from a family member or friend is essential and frequently more revealing than the patient's own account

Cognitive screening tools

These tools screen for and quantify cognitive impairment; none of them alone makes a diagnosis of dementia, which requires the impairment to be shown to be progressive, to affect function, and to have other causes excluded.

Excluding reversible causes

Before attributing cognitive decline to a primary neurodegenerative dementia, a standard panel excludes reversible or contributory causes, some of which are entirely treatable.

Mild cognitive impairment

Mild cognitive impairment (MCI) describes objectively demonstrable cognitive decline that is greater than expected for age but does not yet significantly impair day-to-day function - the functional threshold is what separates it from dementia. It is a useful and increasingly recognised category, but it is not a benign reassurance: a proportion of people with MCI progress to dementia each year, while others remain stable and some revert to normal cognition, particularly where a reversible contributor (depression, medication, sleep disorder, thyroid disease) is identified and treated.

• Identify and correct reversible contributors, since these account for a meaningful share of those who improve
• Address cardiovascular risk factors, which influence progression particularly where there is a vascular component
• Encourage physical activity, cognitive and social engagement, and hearing correction, all associated with better cognitive trajectories
• Arrange planned review to detect functional decline that would indicate progression to dementia, rather than either discharging or over-investigating

Referral to specialist assessment

Suspected dementia, once reversible causes have been reasonably excluded, should be referred to a memory clinic or specialist old age psychiatry/geriatric medicine service for formal diagnosis, subtyping and initiation of any disease-specific treatment. Diagnosis and subtyping (Alzheimer's, vascular, Lewy body, frontotemporal, or mixed) generally requires more detailed neuropsychological assessment and, often, specialist imaging than is available in a single primary care consultation - see the specific subtype articles (³, ⁴, ⁵) for the distinguishing features of each.

Diagnosis disclosure

Communicating a dementia diagnosis draws on the same principles as breaking any significant diagnosis (see the SPIKES-based approach discussed under consultation skills), adapted for the specific sensitivities of a progressive cognitive illness.

• Establish what the patient already knows or suspects, and how much they want to know, before delivering information
• Address the patient directly, even when a family member is present, preserving autonomy and dignity as far as possible
• Give information in manageable amounts, checking understanding, since processing complex new information is itself affected by the condition
• Explore emotional reaction explicitly and allow time for it before moving to practical planning
• Discuss next steps concretely: post-diagnostic support, safety planning, and what happens now, so the consultation ends with a plan rather than only the diagnosis

Post-diagnostic support

A dementia diagnosis should trigger a structured package of support, not end at the point of disclosure.

• Named care coordinator (often a dementia support worker or Admiral Nurse) to help navigate services
• Information and signposting to dementia-specific charities and support groups for both patient and family
• Planning for the future while capacity allows: Lasting Power of Attorney (for finances and for health/welfare decisions), advance care planning, and discussion of future wishes
• Driving: a legal duty to notify the DVLA of a dementia diagnosis exists; some people can continue driving depending on severity and type, assessed individually rather than by diagnosis alone
• Carer assessment and support, recognising the substantial and sustained burden of caring for someone with dementia - see ⁶ on carer support generally
• Safety review: driving, cooking, medication management, and home safety, revisited as the condition progresses
• Regular review of both the patient's condition and the adequacy of support in place, since needs change as dementia progresses

Risk reduction

A substantial proportion of dementia cases worldwide are attributable to potentially modifiable risk factors across the life course, which means dementia risk reduction is a legitimate clinical activity rather than purely a matter of genetic luck. The Lancet Commission on dementia prevention groups these by life stage.

Hearing loss deserves particular emphasis because it is common, easily overlooked and readily treatable - correcting it with hearing aids is associated with better cognitive outcomes, plausibly by maintaining cognitive stimulation and social engagement. Asking about hearing, and checking that existing aids are working and being worn, is a low-cost intervention with a genuine evidence base behind it.

Capacity

A dementia diagnosis does not itself mean a person lacks capacity for any given decision. Capacity is decision-specific and time-specific, assessed under the Mental Capacity Act 2005 framework for the particular decision in question at the particular time it needs to be made - a person may retain capacity for everyday decisions well into the course of dementia while losing capacity earlier for more complex decisions (e.g. managing a large financial transaction). This is covered in detail in the capacity and best interests article; see ⁷.

Red flags

Prognosis

Most dementias are progressive and, currently, without a disease-modifying cure for the majority of cases, though rate of progression varies considerably between individuals and subtypes. The realistic aim of assessment and diagnosis is to identify any reversible contributing factors, initiate appropriate disease-specific and symptomatic treatment where available, and put in place the support, planning and safeguards that meaningfully improve quality of life and safety for both the person with dementia and their carers over the course of the illness.

An important framing point is that dementia is a life-limiting condition, and recognising it as such - rather than only as a cognitive disorder - allows timely palliative and anticipatory care planning. In advanced disease the priorities shift towards comfort, dignity, symptom control and avoiding burdensome interventions such as repeated hospital admission, and these conversations are far better held early, while the person can still contribute to them, than deferred until a crisis forces a decision by default.