Theories for Why Delirium Affects Older People

Why disorders, drugs, and some stressful situations so easily cause delirium in older people is not known. However, there are some theories. One theory involves a chemical called acetylcholine, a type of neurotransmitter. Neurotransmitters are chemicals that enable brain cells to communicate with one another. The level of acetylcholine decreases when the body is stressed, as it is by a disorder, drug, or stressful situation. The brain does not function well without enough acetylcholine. As people age, the brain produces less acetylcholine. Thus, older people are more vulnerable to conditions that cause the level of acetylcholine to decrease further.

Another theory involves chemicals that can harm the brain (toxins). Toxins may be produced when a person has a disorder, or toxins may be ingested, for example, in contaminated food. Certain drugs are toxic if the level of the drug in the blood is high enough. These toxins can circulate in the blood. Normally, the body blocks many of these toxins from entering the brain. But as people age, the body is less able to do so. In older people, toxins may accumulate in the brain and prevent it from functioning normally, making delirium more likely.

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