Dementia

Dementia is an umbrella term for an acquired decline in memory, thinking or other cognitive abilities that interferes with everyday life. It is not a normal part of ageing. A careful assessment must distinguish a gradually progressive dementia from delirium, depression, medicine effects and other potentially treatable causes.

What dementia means Dementia is an umbrella term rather than one single disease. It describes an acquired decline in one or more cognitive abilities that is severe enough to interfere with independent everyday function. Cognition includes memory, attention, language, planning, judgement, visual understanding and social awareness. Different diseases affect these abilities in different patterns. The word acquired matters. Dementia describes a decline from a person's previous level of ability, not a lifelong learning difference or a low score caused by limited education. The effect on daily function also matters. Forgetting a name occasionally is different from repeatedly missing medicines, getting lost on familiar routes or becoming unable to manage previously routine finances. Most causes of dementia are progressive. Symptoms usually develop over months or years and gradually become more extensive, although the rate and pattern vary. Dementia is not a normal part of ageing Ageing can make recall slower. A person may briefly forget a name, need more time to learn a new device or become less efficient when several tasks compete for attention. Normal age related change does not usually cause a steady loss of previously established abilities. It should not repeatedly disrupt safety, communication, personal care or familiar responsibilities. A person with normal ageing often remembers the missing information later or benefits from a reminder. Someone with dementia may forget that an event happened, repeat the same question or lose the ability to complete a familiar sequence. Age is the strongest risk factor for many dementias, but risk is not inevitability. Many older people do not develop dementia. Symptoms deserve assessment at any age when they represent a persistent change from the person's usual ability. Dismissing cognitive decline as 'just getting older' can delay diagnosis and support. Dementia affects more than memory Memory loss is common in Alzheimer's disease, but dementia can begin in other ways. Planning, language, visual processing, behaviour or movement may change first. Someone may struggle to organise a meal despite remembering the ingredients. Another person may speak fluently but lose the meaning of words. Visual spatial problems can make judging distances, finding objects or navigating familiar places difficult. Executive problems can affect planning, switching attention and controlling impulses. Mood, motivation and social behaviour may change. These changes can be mistakenly interpreted as laziness, stubbornness or deliberate misconduct. The pattern provides clues to the underlying disease. It does not allow a reliable subtype diagnosis without a full clinical assessment. Dementia and delirium must not be confused Delirium is an acute disturbance of attention, awareness and thinking. It usually begins over hours or days and often fluctuates during the same day. Dementia usually develops gradually over months or years. Alertness is often relatively stable early on, although some subtypes can cause fluctuations. Delirium is commonly triggered by an acute problem. Infection, dehydration, constipation, urinary retention, pain, surgery, low oxygen, metabolic disturbance and medicines are frequent causes. A person with delirium may be agitated, frightened or hallucinating. They may instead become quiet, sleepy, withdrawn and slow to respond. Quiet or hypoactive delirium is easily missed. Sudden reduced interaction in an older person can be as important as obvious agitation. Delirium is a medical problem, not a stage of dementia Delirium often improves when its causes are identified and treated. Recovery may take days or weeks, and some people do not return immediately to their previous baseline. It is therefore safer to describe delirium as potentially reversible rather than guaranteed to resolve completely. It can expose underlying vulnerability and is associated with serious complications. People with dementia are more likely to develop delirium during illness or hospital admission. This is called delirium superimposed on dementia. A sudden change in someone who already has dementia must not be attributed automatically to their dementia. Their usual level of attention, communication and function provides the comparison. When clinicians cannot distinguish delirium from dementia, NICE advises treating delirium first. Delaying assessment can miss sepsis, stroke, medicine toxicity or another urgent cause. Major causes of dementia Dementia can result from several diseases. Alzheimer's disease is the most common cause in many populations. Other major causes include vascular dementia, dementia with Lewy bodies and frontotemporal dementia. Parkinson's disease can also be followed by dementia. Mixed dementia means more than one disease process contributes. Alzheimer's and vascular pathology commonly coexist, particularly in later life. The subtype matters because the likely symptoms, treatment response and medicine risks differ. However, real presentations do not always fit one textbook pattern. A clinician should explain uncertainty honestly. A working subtype can be revised when new evidence appears. Alzheimer's disease Alzheimer's disease is a progressive neurodegenerative disease. Abnormal amyloid and tau related processes are associated with loss of synapses and neurons. The typical early pattern is difficulty forming and retaining new episodic memories. A person may forget recent conversations, appointments or events and ask the same question repeatedly. Remote memories can appear better preserved early because they were established over many years. This contrast is not absolute. Word finding, navigation, judgement and planning may become affected as the disease progresses. Behavioural and psychological symptoms can occur later or during stress and illness. Alzheimer's disease can present atypically. Some people develop language, visual processing or executive problems before prominent memory loss. Vascular dementia Vascular dementia results from cerebrovascular disease that damages brain networks. Causes include large strokes, multiple smaller infarcts and small vessel disease. The early pattern may involve slowed thinking, reduced attention, planning difficulty and impaired mental flexibility more than isolated memory loss. Decline can occur in steps after strokes, with periods of relative stability. However, vascular cognitive impairment can also progress gradually. Walking difficulty, urinary symptoms, mood change or focal neurological signs may accompany the cognitive pattern. The features depend on the location and extent of damage. Many people have mixed Alzheimer's and vascular disease. A scan showing white matter change does not prove that vascular disease fully explains the symptoms. Dementia with Lewy bodies Dementia with Lewy bodies, often shortened to DLB, is associated with abnormal alpha synuclein deposits called Lewy bodies. Early memory loss may be less prominent than in typical Alzheimer's disease. Attention, alertness, visual processing and executive ability may fluctuate. Recurrent well formed visual hallucinations are a characteristic clue. The person may see people, children or animals that are not present. Spontaneous parkinsonism can cause slowness, rigidity, tremor or reduced movement. REM sleep behaviour disorder and autonomic symptoms may also occur. Fluctuation means more than ordinary good and bad days. Alertness, attention or ability can change markedly over minutes or hours. Frontotemporal dementia Frontotemporal dementia, or FTD, describes disorders that predominantly affect frontal and temporal brain networks. It often begins at a younger age than Alzheimer's disease, although it can occur in later life. Behavioural variant FTD may cause loss of empathy, disinhibition, apathy, impulsivity, rigid routines, altered eating or reduced social judgement. The person may have little insight into the change. Collateral history from someone who knows them well is therefore particularly important. Other forms begin with progressive language difficulty. Speech production, word meaning or grammar may be affected before memory. Treatable causes and contributors must be considered A clinician should investigate reversible or treatable causes before accepting a progressive dementia diagnosis. This does not mean that every suspected dementia disappears after blood tests. It means that treatable contributors should not be overlooked. Some people have both a neurodegenerative disease and a reversible contributor. Treating hypothyroidism, depression or medicine effects can still improve function. The assessment should be proportionate to the presentation. Sudden decline, young age or focal signs justify a broader and more urgent investigation. The label 'reversible dementia' can be misleading because recovery is not always complete. 'Potentially treatable cause of cognitive impairment' is often more accurate. Hypothyroidism An underactive thyroid can cause slowed thinking, low mood, fatigue, constipation and reduced concentration. A thyroid stimulating hormone test, usually with related thyroid testing when indicated, can identify thyroid dysfunction. Treating confirmed hypothyroidism may improve cognition and general function. Improvement can take time. A mildly abnormal thyroid result does not automatically explain substantial cognitive decline. The whole clinical pattern still requires assessment. Thyroid disease and dementia can coexist. Treatment response helps clarify how much each contributed. Vitamin B12 and folate deficiency Vitamin B12 deficiency can cause cognitive symptoms, neuropathy, gait difficulty, anaemia or changes in the tongue. Some people have neurological deficiency without obvious anaemia. Testing is therefore based on the clinical context rather than the blood count alone. Replacement treats the deficiency and may prevent further neurological injury. Recovery depends on severity and duration. Folate deficiency can also affect health and cognition, but folate should not be given blindly when significant B12 deficiency has not been considered. A low or borderline result needs interpretation with symptoms, diet, medicines, absorption problems and confirmatory testing where appropriate. Depression and cognitive symptoms Depression can impair concentration, processing speed, motivation and memory. Severe depression can resemble dementia. The older term 'pseudodementia' is sometimes used for depression related cognitive impairment. It is imprecise because the symptoms and disability are real. Depression can improve with treatment, and cognition may improve alongside mood. It can also coexist with or precede a neurodegenerative disease. A person with depression may emphasise failure, answer 'I do not know' quickly or vary with effort, but these clues are not diagnostic. Assessment should cover mood, loss of interest, sleep, appetite, guilt, hopelessness and self harm risk while continuing to evaluate cognition and function. Medicine related cognitive impairment Medicines with anticholinergic effects can impair attention, memory and alertness. The total anticholinergic burden may come from several drugs. Sedatives, opioids, some bladder medicines, some antihistamines and other psychoactive medicines can also contribute. Recent dose changes, duplicate prescriptions, over the counter products and alcohol should be reviewed. Stopping a suspected medicine suddenly may be unsafe. The original indication, withdrawal risk and alternatives must be considered. A structured medication review can reduce avoidable cognitive burden while preserving necessary treatment. Normal pressure hydrocephalus Normal pressure hydrocephalus, or NPH, involves enlarged brain ventricles and disturbed cerebrospinal fluid dynamics. The classic pattern combines gait difficulty, cognitive decline and urinary urgency or incontinence. Not every person has all three features. Walking change is often prominent and may look slow, broad based or as though the feet are stuck to the floor. Brain imaging may suggest NPH but does not confirm that symptoms will respond to treatment. Specialist assessment may include further testing. Selected patients can improve after cerebrospinal fluid diversion with a shunt. This possibility makes the gait, continence and cognitive combination important to recognise. Why information from someone who knows the person is essential A cognitive assessment should include the person's account and, with appropriate consent, information from someone who knows them well. The person may minimise changes, lack insight or remember events differently. Family members can also overestimate problems or interpret conflict as illness. Collateral history is therefore evidence, not an automatic truth. Clinicians compare accounts and look for specific examples. Useful examples include missed bills, spoiled food, repeated questions, unsafe driving, getting lost, altered hygiene or personality change. The timeline is crucial. Knowing what changed first, how quickly and with what functional effect often contributes more than one test score. Cognitive screening tools Cognitive screening tools sample abilities such as orientation, memory, attention, language, executive function and visual spatial processing. Examples used in different settings include the Mini Mental State Examination, Montreal Cognitive Assessment and Addenbrooke's Cognitive Examination III. These are often shortened to MMSE, MoCA and ACE III. Other brief tools may be used in primary care or acute settings. The tool chosen depends on the service, suspected pattern, language, sensory needs and clinician training. A screening tool does not measure every cognitive function. It cannot identify the cause of impairment by itself. Why scores require context Education, literacy, language and cultural familiarity can affect test performance. Hearing, vision, fatigue, anxiety and pain can also change results. A person with highly developed previous abilities may have meaningful decline while still scoring within a broad normal range. Another person may score poorly because the test is not accessible, despite maintaining stable daily function. Repeated practice can improve scores without changing the underlying disease. Different tools and versions are not directly interchangeable. NICE advises not ruling out dementia solely because one cognitive score is normal. Function and information from someone who knows the person remain essential. Physical and neurological examination The examination looks for causes and complications rather than merely confirming forgetfulness. Clinicians assess cardiovascular status, hydration, nutrition, gait, vision, hearing and signs of systemic illness. A neurological examination may identify weakness, abnormal reflexes, parkinsonism, eye movement changes, coordination problems or peripheral neuropathy. Gait disturbance with urinary symptoms may raise concern about NPH. Focal signs may suggest stroke, tumour or another structural lesion. The examination also establishes baseline mobility and frailty, which influence care planning and treatment risk. Blood tests and other basic investigations Blood tests are chosen to identify treatable contributors and assess general health. Common tests may include a full blood count, kidney and liver function, electrolytes, calcium, glucose or HbA1c, thyroid function, vitamin B12 and folate. Additional tests depend on symptoms, background and examination. Infection, HIV, syphilis, autoimmune disease or toxic exposure are not screened indiscriminately in every person. Urine testing may be appropriate when symptoms suggest infection or another urinary problem. A positive result without symptoms does not automatically explain cognitive decline. The investigation plan should answer clinical questions rather than become a fixed checklist detached from the person. Brain imaging NICE recommends structural imaging to exclude reversible causes and assist subtype diagnosis unless dementia is already well established and the subtype is clear. CT can identify major strokes, tumours, subdural collections, hydrocephalus and substantial atrophy. MRI provides more detail about small vessel disease, infarcts, regional atrophy and other structural changes. Imaging patterns can support Alzheimer's disease, vascular dementia or frontotemporal dementia. They are not perfectly specific. A scan must be interpreted with clinical findings. Vascular lesions, atrophy and white matter changes can occur without explaining the person's full syndrome. Capacity is not lost automatically Mental capacity means the ability to make a particular decision at the time it needs to be made. A dementia diagnosis does not prove that a person lacks capacity. Capacity must be presumed unless there is evidence that assessment is needed. Capacity is decision specific. Someone may decide what to eat or wear while needing help with a complex property transaction. Capacity can also vary with time and circumstances. Delirium, pain, fatigue, communication barriers and medicine effects can temporarily impair decision making. An unwise decision is not, by itself, proof of incapacity. Supporting decision making Before concluding that someone cannot decide, reasonable steps should help them understand and communicate. Information may be simplified, repeated or presented visually. Hearing aids, interpreters, familiar supporters and a quieter environment can help. The decision may be delayed until delirium, pain or exhaustion improves when delay is safe. A person has capacity for a decision when they can understand relevant information, retain it long enough, use or weigh it and communicate a choice. The assessment should focus on the specific decision, not a general impression that the person is confused. Best interests and planning ahead If a person lacks capacity for a specific decision, the authorised decision maker must act within the relevant legal framework. In England and Wales, the Mental Capacity Act requires a best interests process that considers wishes, beliefs, values and the least restrictive option. Family members provide important information but do not automatically gain legal authority because of their relationship. A lasting power of attorney can appoint trusted people for property and financial affairs or health and welfare decisions. An LPA must be created while the person has capacity to make that arrangement. Early planning preserves choice rather than removing it. Driving and dementia Driving depends on attention, judgement, visual processing, reaction, memory and insight. A diagnosis does not mean every person loses all these abilities on the same day. In Great Britain, a person diagnosed with dementia must notify the Driver and Vehicle Licensing Agency and should tell their motor insurer. DVLA may request medical information and decide whether a licence can continue, needs review or must stop. The clinician does not personally issue the licence. The rules differ in Northern Ireland, where the Driver and Vehicle Agency applies. People outside the UK should check their own licensing authority. Continuing to drive when unsafe creates serious risk. Planning alternative transport early can reduce isolation and conflict. Cholinesterase inhibitors Cholinesterase inhibitors increase acetylcholine signalling. Donepezil, galantamine and rivastigmine are the main drugs in this class. NICE recommends them as options for mild to moderate Alzheimer's disease. Donepezil or rivastigmine are also used in dementia with Lewy bodies. These medicines can modestly improve or stabilise cognition, function or behaviour for some people. They do not cure dementia or stop all progression. Common adverse effects include nausea, diarrhoea, reduced appetite and weight loss. They can also slow the heart rate and contribute to fainting in susceptible people. Treatment choice and monitoring should consider cardiac history, falls, weight, interactions, adherence and the person's goals. Memantine Memantine acts mainly on NMDA type glutamate receptors. It has a different mechanism from cholinesterase inhibitors. NICE recommends memantine alone for severe Alzheimer's disease and for moderate Alzheimer's disease when cholinesterase inhibitors are not tolerated or are contraindicated. It may be added to a cholinesterase inhibitor in established moderate or severe Alzheimer's disease according to guidance. Memantine can also be considered in DLB when cholinesterase inhibitors are unsuitable. Possible adverse effects include dizziness, headache and constipation. Benefits are usually modest and should be reviewed in terms of function and wellbeing. Medicines depend on the subtype Cholinesterase inhibitors and memantine are not universal dementia treatments. They are not recommended for frontotemporal dementia because evidence does not show appropriate benefit and symptoms may differ. For vascular dementia, NICE recommends considering these drugs only when comorbid Alzheimer's disease, DLB or Parkinson's disease dementia is suspected. Dementia treatment should therefore follow a reasoned subtype assessment rather than the word dementia alone. Stopping a cholinesterase inhibitor solely because Alzheimer's disease has become severe is not recommended. Adverse effects, goals and ongoing benefit still require review. Distress and behaviour communicate needs Agitation, shouting, resistance or wandering may reflect pain, fear, boredom, constipation, infection, delirium, hunger or an unfamiliar environment. The behaviour should not be treated as a diagnosis. A structured assessment looks for clinical, social and environmental causes. Communication may have become difficult. Repeated questioning can reflect anxiety or failure to retain reassurance. Changes in routine, excessive noise, poor lighting or unfamiliar staff can increase distress. The first response is usually to understand the trigger and modify care, not to suppress behaviour with a sedating medicine. Non pharmacological management NICE recommends tailored activities that promote wellbeing. Meaningful activity should reflect the person's interests, culture, abilities and previous routines. Group cognitive stimulation therapy can support people with mild to moderate dementia. It involves structured themes and social engagement. Occupational therapy or cognitive rehabilitation can help maintain chosen activities through strategies, prompts and environmental adaptation. Regular physical activity, daylight, social contact, sleep routines and treatment of hearing or vision problems can support function. These approaches are not cures. Their purpose is to preserve participation, reduce distress and improve quality of life. Supporting carers and families Dementia affects families, friends and unpaid carers as well as the person diagnosed. Carers need information about the subtype, expected changes, communication, distress, medicines and available services. Training and psychoeducation can help carers respond to behaviour, plan meaningful activities and protect their own health. Carer strain can lead to exhaustion, depression, conflict or breakdown of care. Asking directly about sleep, finances and coping is clinically important. A carer's assessment and respite support may be available. Accepting support is not a failure of commitment. Antipsychotics are not routine dementia treatment Antipsychotic medicines can reduce severe psychosis or aggression in selected situations. Their potential benefit is limited and their risks are substantial. NICE advises using them only when the person is at risk of harming themselves or others, or when agitation, hallucinations or delusions cause severe distress. Pain, delirium, infection, constipation, medicine effects and environmental causes should be assessed first. Psychosocial and environmental interventions should continue even when an antipsychotic is prescribed. The lowest effective dose should be used for the shortest possible time, with reassessment at least every six weeks. The mortality and stroke warning Antipsychotics are associated with increased cerebrovascular events, including stroke, and increased mortality in older people with dementia. UK MHRA safety advice emphasises these risks. Most antipsychotic use for dementia related behavioural symptoms is off label, with narrow licensed exceptions. In the United States, antipsychotic labels carry a boxed warning that older patients with dementia related psychosis treated with these drugs have an increased risk of death. The FDA boxed warning specifically concerns increased mortality. Product warnings also describe cerebrovascular adverse reactions, including stroke, in older patients with dementia related psychosis. This does not mean antipsychotics can never be used. It means the indication, alternatives, expected benefit, risks and review plan must be explicit. Particular risk in dementia with Lewy bodies DLB and Parkinson's disease dementia can cause severe antipsychotic sensitivity. The person may develop profound rigidity, reduced consciousness, worsening confusion or life threatening reactions. Visual hallucinations may be tolerated or even recognised as unreal. Treatment should focus on distress and risk rather than the presence of a hallucination alone. If medicine is considered, specialist advice is important. Drugs with strong dopamine blocking effects can be especially problematic. Families and care staff should know that sudden deterioration after an antipsychotic requires urgent medical review. Rapid progression is not routine dementia Most common neurodegenerative dementias progress over years. Noticeable decline over weeks or a few months is atypical. Rapid progression can result from delirium, autoimmune encephalitis, infection, prion disease, cancer, seizures, toxins or metabolic disturbance. The person may need urgent neurological assessment, MRI, electroencephalography, cerebrospinal fluid testing or other targeted investigations. Rapid deterioration should not wait for a routine memory clinic pathway when serious or treatable disease is possible. The urgency depends on associated symptoms, examination findings and the person's overall condition. Young onset cognitive decline Young onset dementia generally refers to dementia beginning before age 65. The range of possible causes is broader than in very late life. Frontotemporal dementia, genetic disease, autoimmune conditions, alcohol related brain injury and atypical Alzheimer's presentations require consideration. Work, parenting, finances and relationships may be affected differently. Services should address these practical needs. A strong health problems in the family or characteristic syndrome may justify genetic counselling. Genetic testing should not be arranged casually without informed discussion. Age should never be used to dismiss progressive cognitive or behavioural change. Focal neurological signs and other atypical clues New unilateral weakness, sensory loss, visual field loss, speech disturbance or severe gait change suggests focal brain disease. Headache, seizures, fever, weight loss, previous cancer or immunosuppression can alter the differential diagnosis. Prominent early movement disorder, eye movement abnormality or cerebellar signs may indicate another neurodegenerative or structural condition. Cognitive decline with gait disturbance and urinary symptoms raises the possibility of NPH, although the combination has several causes. These patterns require targeted assessment rather than automatic placement on a routine dementia pathway. What good dementia care aims to achieve Good care seeks an accurate diagnosis without reducing the person to a label. It treats reversible contributors, supports remaining abilities and reduces avoidable risk. It includes the person's voice, uses collateral information carefully and respects confidentiality. It supports carers while recognising that the person's interests and the carer's interests may not always be identical. It revisits diagnosis, capacity, medicines, driving, safety and future planning as circumstances change. The central aim is not only longer survival or a higher test score. It is the best possible function, dignity, participation and comfort for that individual.

Dementia is an acquired decline in cognition that interferes with everyday function, but it should never be diagnosed from forgetfulness or one test score alone. A gradual pattern supports dementia, while a sudden or fluctuating change must be treated as possible delirium until an acute cause has been assessed.