Health

Alzheimer's disease (AD), also known in medical literature as Alzheimer disease, is the most common form of dementia. There is no cure for the disease, which worsens as it progresses, and eventually leads to death. It was first described by German psychiatrist and neuropathologist Alois Alzheimer in 1906 and was named after him.[1]

Most often, AD is diagnosed in people over 65 years of age,[2] although the less-prevalent early-onset Alzheimer's can occur much earlier. In 2006, there were 26.6 million sufferers worldwide. Alzheimer's is predicted to affect 1 in 85 people globally by 2050.[3]

Although Alzheimer's disease develops differently for every individual, there are many common symptoms.[4] Early symptoms are often mistakenly thought to be 'age-related' concerns, or manifestations of stress.[5] In the early stages, the most common symptom is difficulty in remembering recent events. When AD is suspected, the diagnosis is usually confirmed with tests that evaluate behaviour and thinking abilities, often followed by a brain scan if available.[6]

As the disease advances, symptoms can include confusion, irritability and aggression, mood swings, trouble with language, and long-term memory loss. As the sufferer declines they often withdraw from family and society.[5][7] Gradually, bodily functions are lost, ultimately leading to death.[8] Since the disease is different for each individual, predicting how it will affect the person is difficult. AD develops for an unknown and variable amount of time before becoming fully apparent, and it can progress undiagnosed for years. On average, the life expectancy following diagnosis is approximately seven years.[9] Fewer than three percent of individuals live more than fourteen years after diagnosis.[10]

The cause and progression of Alzheimer's disease are not well understood. Research indicates that the disease is associated with plaques and tangles in the brain.[11] Current treatments only help with the symptoms of the disease. There are no available treatments that stop or reverse the progression of the disease. As of 2008[update], more than 500 clinical trials have been conducted to find ways to treat the disease, but it is unknown if any of the tested treatments will work.[12] Mental stimulation, exercise, and a balanced diet have been suggested as possible ways to delay symptoms in healthy older individuals, but they have not been proven as effective.[13]

Because AD cannot be cured and is degenerative, the sufferer relies on others for assistance. The role of the main caregiver is often taken by the spouse or a close relative.[14] Alzheimer's disease is known for placing a great burden on caregivers; the pressures can be wide-ranging, involving social, psychological, physical, and economic elements of the caregiver's life.[15][16][17] In developed countries, AD is one of the most costly diseases to society.[18][19]

Characteristics

The disease course is divided into four stages, with progressive patterns of cognitive and functional impairments.

Pre-dementia

The first symptoms are often mistakenly attributed to aging or stress.[5] Detailed neuropsychological testing can reveal mild cognitive difficulties up to eight years before a person fulfills the clinical criteria for diagnosis of AD.[20] These early symptoms can affect the most complex daily living activities.[21] The most noticeable deficit is memory loss, which shows up as difficulty in remembering recently learned facts and inability to acquire new information.[20][22]

Subtle problems with the executive functions of attentiveness, planning, flexibility, and abstract thinking, or impairments in semantic memory (memory of meanings, and concept relationships) can also be symptomatic of the early stages of AD.[20] Apathy can be observed at this stage, and remains the most persistent neuropsychiatric symptom throughout the course of the disease.[23] The preclinical stage of the disease has also been termed mild cognitive impairment,[22] but whether this term corresponds to a different diagnostic stage or identifies the first step of AD is a matter of dispute.[24]

Early

In people with AD the increasing impairment of learning and memory eventually leads to a definitive diagnosis. In a small portion of them, difficulties with language, executive functions, perception (agnosia), or execution of movements (apraxia) are more prominent than memory problems.[25] AD does not affect all memory capacities equally. Older memories of the person's life (episodic memory), facts learned (semantic memory), and implicit memory (the memory of the body on how to do things, such as using a fork to eat) are affected to a lesser degree than new facts or memories.[26][27]

Language problems are mainly characterised by a shrinking vocabulary and decreased word fluency, which lead to a general impoverishment of oral and written language.[25][28] In this stage, the person with Alzheimer's is usually capable of adequately communicating basic ideas.[25][28][29] While performing fine motor tasks such as writing, drawing or dressing, certain movement coordination and planning difficulties (apraxia) may be present but they are commonly unnoticed.[25] As the disease progresses, people with AD can often continue to perform many tasks independently, but may need assistance or supervision with the most cognitively demanding activities.[25]

Moderate

Progressive deterioration eventually hinders independence; with subjects being unable to perform most common activities of daily living.[25] Speech difficulties become evident due to an inability to recall vocabulary, which leads to frequent incorrect word substitutions (paraphasias). Reading and writing skills are also progressively lost.[25][29] Complex motor sequences become less coordinated as time passes and AD progresses, so the risk of falling increases.[25] During this phase, memory problems worsen, and the person may fail to recognise close relatives.[25] Long-term memory, which was previously intact, becomes impaired.[25]

Behavioural and neuropsychiatric changes become more prevalent. Common manifestations are wandering, irritability and labile affect, leading to crying, outbursts of unpremeditated aggression, or resistance to caregiving.[25] Sundowning can also appear.[30] Approximately 30% of people with AD develop illusionary misidentifications and other delusional symptoms.[25] Subjects also lose insight of their disease process and limitations (anosognosia).[25] Urinary incontinence can develop.[25] These symptoms create stress for relatives and caretakers, which can be reduced by moving the person from home care to other long-term care facilities.[25][31]

Advanced

During this last stage of AD, the person is completely dependent upon caregivers.[25] Language is reduced to simple phrases or even single words, eventually leading to complete loss of speech.[25][29] Despite the loss of verbal language abilities, people can often understand and return emotional signals.[25] Although aggressiveness can still be present, extreme apathy and exhaustion are much more common results.[25] People with AD will ultimately not be able to perform even the simplest tasks without assistance.[25] Muscle mass and mobility deteriorate to the point where they are bedridden, and they lose the ability to feed themselves.[25] AD is a terminal illness, with the cause of death typically being an external factor, such as infection of pressure ulcers or pneumonia, not the disease itself.[25]