The course of<unk> 's is generally described in three stages, with a progressive pattern of cognitive and functional impairment. The three stages are described as early or mild, middle or moderate, and late or severe. The disease is known to target the hippocampus which is associated with memory, and this is responsible for the first symptoms of memory impairment. As the disease progresses so does the degree of memory impairment. First symptoms Stages of atrophy in<unk> 's. The first symptoms are often mistakenly attributed to aging or stress. Detailed neuropsychological testing can reveal mild cognitive difficulties up to eight years before a person fulfills the clinical criteria for diagnosis of<unk> . These early symptoms can affect the most complex activities of daily living. The most noticeable deficit is short term memory loss, which shows up as difficulty in remembering recently learned facts and inability to acquire new information. 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<unk> . Apathy and depression can be seen at this stage, with apathy remaining as the most persistent symptom throughout the course of the disease. The preclinical stage of the disease has also been termed mild cognitive impairment (MCI). This is often found to be a transitional stage between normal aging and dementia. MCI can present with a variety of symptoms, and when memory loss is the predominant symptom, it is termed amnestic MCI and is frequently seen as a prodromal stage of<unk> . Amnestic MCI has a greater than 90% likelihood of being associated with<unk> 's. Early stage In people with<unk> , the increasing impairment of learning and memory eventually leads to a definitive diagnosis. In a small percentage, difficulties with language, executive functions, perception (agnosia), or execution of movements (apraxia) are more prominent than memory problems.<unk>  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 or how to drink from a glass) are affected to a lesser degree than new facts or memories. Language problems are mainly characterised by a shrinking vocabulary and decreased word fluency, leading to a general impoverishment of oral and written language. In this stage, the person with<unk> 's is usually capable of communicating basic ideas<unk> equately. 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. As the disease progresses, people with<unk>  can often continue to perform many tasks independently, but may need assistance or supervision with the most cognitively demanding activities. Middle stage Progressive deterioration eventually hinders independence, with subjects being unable to perform most common activities of daily living. 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. Complex motor sequences become less coordinated as time passes and<unk>  progresses, so the risk of falling increases. During this phase, memory problems worsen, and the person may fail to recognise close relatives. Long-term memory, which was previously intact, becomes impaired. Behavioral and neuropsychiatric changes become more prevalent. Common manifestations are wandering, irritability and emotional lability, leading to crying, outbursts of unpremeditated aggression, or resistance to caregiving. Sundowning can also appear. Approximately 30% of people with<unk>  develop illusionary misidentifications and other delusional symptoms. Subjects also lose insight of their disease process and limitations (anosognosia). Urinary incontinence can develop. These symptoms create stress for relatives and caregivers, which can be reduced by moving the person from home care to other long-term care facilities. Late stage A normal brain on the left and a late-stage<unk> 's brain on the right During the final stage, known as the late-stage or severe stage, there is complete dependence on caregivers. Language is reduced to simple phrases or even single words, eventually leading to complete loss of speech. Despite the loss of verbal language abilities, people can often understand and return emotional signals. Although aggressiveness can still be present, extreme apathy and exhaustion are much more common symptoms. People with<unk>  will ultimately not be able to perform even the simplest tasks independently; muscle mass and mobility deteriorates to the point where they are bedridden and unable to feed themselves. The cause of death is usually an external factor, such as infection of pressure ulcers or pneumonia, not the disease itself.
Alzheimer's disease
Lewy body dementias
Parkinson's disease dementia
Down syndrome
Vascular dementia
Aging brain
Alcohol-related dementia
Chronic traumatic encephalopathy