Causes of Dementia

Dementia is caused by many conditions that affect the brain. Some causes of dementia can be reversed, and others cannot.

Treatable conditions that can cause dementia include a high fever, dehydration, vitamin deficiency and poor nutrition, bad reactions to medicines, problems with the thyroid gland, or a minor head injury. Medical conditions like these can be serious and should be treated by a doctor as soon as possible.

Conditions or diseases that cause irreversible dementia, especially in older people, include Alzheimer's disease (AD), dementia with Lewy bodies, and multi-infarct dementia (MID), also called vascular dementia.

• Alzheimer's disease. AD is the most common cause of dementia. In AD, nerve cells in the brain die. The causes of the brain damage of AD are not yet clear. Symptoms of AD begin slowly with memory problems and become steadily worse. Over time, the brain damage in AD leads to serious problems in thinking, judgment, and the ability to carry out daily activities.

• Dementia with Lewy bodies. This type of dementia is the second most common cause of dementia in older adults. Lewy bodies are abnormal structures found in certain areas of the brain. It is not yet clear whether dementia with Lewy bodies is a separate illness or perhaps a variant of AD or Parkinson's disease.

• Multi-infarct or vascular dementia. In MID, small strokes occur, and blood clots in the blood vessels in the brain cause the death of brain tissue. Symptoms that begin suddenly may be a sign of this kind of dementia. High blood pressure is a cause of strokes and MID.

Other less common causes of dementia include Huntington's disease, Parkinson's disease, Pick's disease, Binswanger's disease, and AIDS.

Sometimes depression in older people is mistaken for dementia.