Alzheimer's disease is caused by changes in the brain. Some of the symptoms may be related to a loss of chemical messengers in the brain. These messengers are called neurotransmitters. They allow nerve cells in the brain to communicate properly.

People with Alzheimer's disease have two things in the brain that aren't normal.

• Amyloid plaques are clumps of a protein called beta amyloid. This plaque builds up around the cells in the brain that communicate with each other.
• Neurofibrillary tangles are made from a protein called tau. Normally, the tau protein helps cells communicate in the brain. In Alzheimer's disease, the tau protein twists and tangles. The tangles clump together, and some nerve cells die. This makes communication in the brain much harder.

As brain cells die, the brain shrinks. Over time, the damage to the brain causes problems with memory, intelligence, judgment, language, and behavior.

Experts don't know if amyloid plaques and neurofibrillary tangles are side effects of Alzheimer's disease or if they're part of the cause.