Alzheimer's disease is the name given to a form of cortical dementia, affecting higher mental functions and is the most common cause of dementia. Patients experience irreversible global, progressive impairment of brain function, leading to reduced intellectual ability. Neurodegeneration in Alzheimer's disease is estimated to start 20-30 years before clinical onset.EpidemiologyAlzheimer's disease is the most common form of dementia, accounting for 50%-60% of all cases.1,2The prevalence of dementia is below 1% in individuals aged 60-64 years, but shows an almost exponential increase with age, so that in people aged 85 years or older the prevalence is between 24% and 33% in the Western world.Sporadic Alzheimer's disease is very common with more than 15 million people affected worldwide.1 The cause of the sporadic form of the disease is unknown, probably because the disease is heterogeneous, caused by ageing in concert with a complex interaction of both genetic and environmental risk factors.

Familial Alzheimer's disease is a very rare autosomal dominant disease with early onset.3Risk factorsAgeing.Caucasian.More common in women.Apolipoprotein E4 variant (associated with an increased risk of Alzheimer's disease presenting at an earlier age).Risk factors associated with vascular disease, i.e. hypercholesterolaemia, hypertension, atherosclerosis, coronary heart disease, smoking, obesity and diabetes.Sporadic Alzheimer's disease has been shown to have a significant genetic background. A large population-based twin study showed that the extent of heritability for the sporadic disease is almost 80%. Studies have suggested that the risk of the disease is reduced in patients treated with non-steroidal anti-inflammatory drugs.DiagnosisThe DSM-IV criteria for dementia of the Alzheimer's type are:The development of multiple cognitive defects manifested by both:Memory impairment: impaired ability to learn new information as well as recall previously learned information.One or more of the following cognitive disturbances:Language disturbance.

Apraxia (inability to carry out motor activities despite intact motor function).Agnosia (failure to recognise or identify objects despite intact sensory function).Senior Moving Services San DiegoDisturbance of planning, organising, sequencing, abstracting and other higher functioning.Window Cleaning Pole AccessoriesOther featuresThe cognitive deficits cause significant impairment in social or occupational functioning and represent a significant decline from a previous level of functioning.Hanging Mirror With Fishing LineThe course of the illness includes a gradual onset and continuing cognitive decline.The cognitive deficits are not due to any central nervous system conditions, systemic conditions or substance-induced conditions.

The deficits do not occur exclusively during a period of acute confusional state.The disorder is not better accounted for by any other neuropsychiatric disorder, e.g. depression, schizophrenia.PresentationStan has had Alzheimer’s disease for 10 years. He is cared for by his wife Denise, who helped set up the Maidstone branch of the Alzheimer’s Society and runs the helpline. Last year, she was awarded an MBE for services to her local community. Short video from NHS Choices. Alzheimer's disease is a slowly progressive disorder, with insidious onset and progressive impairment of episodic memory; instrumental signs include aphasia, apraxia, and agnosia, together with general cognitive symptoms, such as impaired judgement, decision-making and orientation. Behavioural signs, such as aggression, psychomotor agitation and psychosis (hallucinations and delusions), are very common in patients with Alzheimer's disease, especially in the late stages of the disease. Features include:Memory: both recall and new memory formation are affected early causing a severe amnesia.

Aphasia occurs fairly early: difficulties with word meaning, word finding, object naming and definitions.Attention and visuospatial problems are quite common.Personality and behaviour are well preserved until later stages.Visuospatial, perceptual and problem-solving skills are initially preserved.Neurological examination is normal.A score of 23/30 in the mini mental state examination (MMSE) is generally considered to be diagnostic of dementia.Criteria for the clinical diagnosis of PROBABLE Alzheimer's disease4Dementia established by clinical examination and documented by the MMSE or some similar examination and confirmed by neuropsychological tests.Deficits in two or more areas of cognition.Progressive worsening of memory and other cognitive functions.No disturbance of consciousness.Onset between ages of 40 and 90, most often after the age of 65.Absence of systemic disorders or other brain diseases that could account for the symptoms.The diagnosis of PROBABLE Alzheimer's diseaseThis is supported by progressive deterioration of specific cognitive functions such as language (aphasia), motor skills (apraxia), and perceptions (agnosia).

Impaired activities of daily living and altered patterns of behaviour.Family history of similar disordersNormal lumbar puncture, normal pattern or nonspecific changes in EEG, evidence of cerebral atrophy on CT scan with progression documented by serial observation.Other clinical features consistent with the diagnosis of PROBABLE Alzheimer's diseasePlateaus in the course of progression of the illness.Associated symptoms of depression, insomnia, incontinence, delusions, illusions, hallucinations.Catastrophic verbal, emotional or physical outbursts, sexual disorders and weight loss.Other neurological abnormalities in some patients, especially with more advanced disease.Differential diagnosisCognitive changes with ageing may be very difficult to distinguish in the mildly affected, early stages of Alzheimer's disease.Other forms of dementia - see separate article Dementia.Normal pressure hydrocephalus.Hypothyroidism.Drug-induced cognitive impairment, e.g. benzodiazepines.Acute confusional state, amnesia.

Neurosyphilis, AIDS dementia complex.InvestigationsThere are several tools available for screening for cognitive impairment. Other routine investigations are detailed in the separate Dementia article.This is a PET (positron emission tomography) scan of the brain of a person with Alzheimerʼs disease showing a loss of function (no red areas) in the temporal lobes. Blood flow to these areas of the brain is being measured indirectly. Red areas show more accumulated radioactivity and blue areas are where low or no radioactivity has accumulated. Compare with the PET scan of a brain without AD (next image) - where there are far more red areas.Associated diseasesAbout 50% of patients with neuropathological disease have significant concomitant cerebrovascular pathology.There is also a large overlap in pathology between Alzheimer's disease and Lewy body dementia.ManagementManagement must focus both on treating patients and on supporting their carers. A co-ordinated and integrated multi-agency approach is required in the treatment and care of people with dementia and their carers.

Ideally there should be locally agreed written policies and a combined care plan agreed by health and social services that takes into account the changing needs of the person with dementia and his or her carers.5 Such support may include respite care, day centres or longer-term residential care.There should be named health and/or social care staff to operate the care plan.The plan should be endorsed by the person with dementia and/or carers.Formal reviews of the care plan should occur.Early referral is indicated in young patients with Alzheimer's disease - they often have different needs to older patients, e.g. driving.Valid consent for treatment5Health and social care professionals should always seek valid consent from people with dementia:This should entail informing the person of options and checking that he or she understands.Checking also that there is no coercion and that he or she continues to consent over time.If the person lacks the capacity to make a decision, the provisions of the Mental Capacity Act 2005 must be followed.