Alzheimer's disease is a neurodegenerative disease that typically affects adults over 65 years old. The disease is caused by abnormally high levels of beta amyloid protein and tau protein. The beta amyloid protein clusters in high numbers between neurons and eventually impede the signaling of the neurons, leading to death of the neurons. The tau proteins structure the microtubules in the axons. In alzheimer's the tau proteins deform and they impede the trasnport of molecules form the soma to the axon terminal. This also eventually impedes the signaling of the neurons and causes neuron death. Late onset alzheimer's disease has a genetic pre disposition involed in it, unlike early onset alzheimer's where there is a genetic mutation that can be passed from generation to generation. In late onset alzheimer's disease, the e4 allele of the APOE gene causes the pre disposition to the disease. The APOE gene is involved in trasnporting cholesterol and lipoproteins. It is believed that this allele in the APOE gene is a predisposition to cardiovascular disease as well as alzheimer's. cholesterol is mainly used by astrocytes which would ideally remove the amyloid plaques, but they don't in alzheimer's patients.