Alzheimer's disease (AD) is an acquired disorder of cognitive and behavioral impairment that markedly interferes with social and occupational functioning. It is an incurable disease with a long and progressive course. In AD, senile plaques and neurofibrillary tangles develop in the hippocampus, a structure deep in the brain that helps to encode memories, and in other areas of the cerebral cortex that are used in thinking and making decisions.

The cause is unknown; several investigators believe that converging environmental and genetic risk factors trigger a pathophysiologic cascade that, over decades, leads to Alzheimer's pathology and dementia.
AD affects the three processes that keep neurons healthy: communication, metabolism, and repair. Certain nerve cells in the brain stop working, lose connections with other nerve cells, and finally die. The destruction and death of these nerve cells causes the main features of the disease: memory failure, personality changes, problems in carrying out daily activities, etc.

Signs and symptoms
- Preclinical AD The patient may appear completely normal on physical examination and mental status testing.
- Mild AD The patient may have the following signs: memory loss, confusion about the location of familiar places, trouble accomplishing normal daily tasks, compromised judgment, mood and personality changes, and increased anxiety.
- Moderate AD The patient may have the following signs: increased memory loss and confusion; shortened attention span; problems recognizing friends and family members; difficulty with language; problems with reading, writing, and working with numbers; restlessness; agitation; anxiety; tearfulness; wandering, especially in the late afternoon or at night; hallucinations; delusions; suspiciousness or paranoia; irritability; and perceptual-motor problems.
- Severe AD The patient cannot recognize family or loved ones and cannot communicate in any way. They are completely dependent on others for care, and all sense of self seems to vanish. Other symptoms can include weight loss, difficulty swallowing, increased sleeping, and lack of bladder and bowel control.
In end-stage AD, patients may be in bed much or all of the time. Death is often the result of other illnesses, frequently aspiration pneumonia.

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Adapted from Medscape Drugs & Diseases. Alzheimer Disease. Available at http://emedicine.medscape.com/article/1134817-overview#a1. Accessed on September 7, 2016. To view the entire article and all other content on the Medscape Drugs & Diseases site, a free, one-time registration is required.