Alzheimer’s disease accounts for 60-80% of cases. Vascular dementia, which occurs because of microscopic bleeding and blood vessel blockage in the brain, is the second most common cause of dementia. Those who experience the brain changes of multiple types of dementia simultaneously have mixed dementia. There are many other conditions that can cause symptoms of dementia, including some that are reversible, such as thyroid problems and vitamin deficiencies.
Alzheimer’s disease is a degenerative brain disease and the most common form of dementia. Dementia is not a specific disease. It’s an overall term that describes a group of symptoms.
How does Alzheimer’s disease affect the brain?
Scientists continue to unravel the complex brain changes involved in Alzheimer’s disease. Changes in the brain may begin a decade or more before symptoms appear. During this very early stage of Alzheimer’s, toxic changes are taking place in the brain, including abnormal buildups of proteins that form amyloid plaques and tau tangles. Previously healthy neurons stop functioning, lose connections with other neurons, and die. Many other complex brain changes are thought to play a role in Alzheimer’s as well.
The damage initially appears to take place in the hippocampus and the entorhinal cortex, which are parts of the brain that are essential in forming memories. As more neurons die, additional parts of the brain are affected and begin to shrink. By the final stage of Alzheimer’s, damage is widespread and brain tissue has shrunk significantly.