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Dementia is not a single disease, but a general term for memory loss and other intellectual disabilities serious enough to interfere with daily life.

Alzheimer's disease is the most common cause of dementia, among many other causes, such as vascular dementia, which causes brain damage from cerebrovascular or cardiovascular problems, and HIV-associated dementia, or infection of the brain with HIV virus.

The mechanism of dementia is not clear, but dementia results from the death and damage of nerve cells in the brain.

The greatest known risk factor for dementia is advancing age, and the majority of dementia patients are older than 65. There are also patients younger than 50.

Other risk factors include family history, smoking, alcohol use, high cholesterol and diabetes.

In most cases, dementia symptoms gradually worsen over a long period of time. If a person starts to have symptoms, such as short-term memory loss and abrupt changes in behavior and moods, people around them should be alarmed.

Drawing a clock by hand can be used to detect mild cognitive impairment and dementia.

Doctors suggest healthy lifestyles are always good for disease prevention, including dementia, although there are no specific precautions for the condition.