In statistics provided by the Alzheimer's Association's report, 2010 Alzheimer's Disease Facts and Figures, 5.3 million people have the debilitating neurological condition Alzheimer's disease. Most patients have late onset Alzheimer's disease, which begins after the age of 60, though some people may have early onset Alzheimer's disease, which begins before the age of 60. MedlinePlus, a service of the U.S National Library of Medicine and the National Institutes of Health, points out that the early onset type of Alzheimer's disease tends to progress at a rapid pace, causing severe problems in cognitive functions, such as memory, language, judgment and decision-making.
But how does Alzheimer's disease affect the brain? The disease causes numerous changes to the brain, such as alterations in size and the formation of plaques and tangles.
Plaques and Tangles
MedlinePlus notes that three types of plaques and tangles occur: senile plaques, neuritic plaques and neurofibrillary tangles. With the plaques, clusters of dying nerve cells form around protein; neuritic plaques involve the dying nerve cells, while the senile plaques involve the dying nerve cells' products. The type of protein involved in plaque formations is the beta-amyloid protein. The Alzheimer's Association points out that small groups of beta-amyloid protein “may block cell-to-cell signaling at synapses” and “activate immune system cells that trigger inflammation and devour disabled cells.”
With the tangles, pieces of protein become intertwined within the nerve cells. The type of protein involved in tangles is the tau protein. Normally, the tau protein helps keep a vital cell transportation's “tracks” straight, but in Alzheimer's disease, they become tangled, leading to the “tracks” falling apart. The Alzheimer's Association explains that with this transport system, cells cannot receive nutrients, leading to death.
Hippocampus, Cortex and Ventricles
Alzheimer's disease causes other changes to the brain besides the formation of plaques and tangles. One area affected by the disease is the hippocampus, a brain structure located in the temporal lobe. The hippocampus plays a large role in memory: it consolidates short-term memories into long-term memories. In Alzheimer's disease patients, the hippocampus becomes significantly smaller, which affects patients' ability to form new memories. Another brain region that becomes smaller in Alzheimer's disease patients is the cerebral cortex, which plays a role in memory, planning and thinking. One area of the brain does become larger in Alzheimer's disease patients' brains: the ventricles, a part of the brain filled with cerebrospinal fluid. The Alzheimer's Association has an image showing the differences between a healthy brain and the brain of a patient with advanced Alzheimer's disease.
Time Frame
The changes that occur in the brain of an Alzheimer's disease patient take time. The Alzheimer's Association explains that changes may start 20 or more years before the patient becomes diagnosed with Alzheimer's disease.