The cause of Alzheimer's disease (AD) is currently unknown, but various factors have been identified that may contribute to the disease progression. The formation of proteins such as amyloid plaques and neurofibrillary tangles between nerve cells in the brain are thought to cause the degradation of neurons and lead to the symptoms of the disease. There is also a reduced presence of acetylcholine in AD brains, which is essential for normal cognitive function.
There have also been various risk factors identified, which may affect the likeliness of developing the disease:
- Age - this is the biggest risk factor with over half of people over the age of 85 developing the disease
- Genetics - the majority of cases are late onset, occuring over the age of 65 with no obvious genetic link. However, a few genes have been identified to affect the probability of developing disease, such as Apoliprotein E. There are three forms of this gene: ApoE 2, 3 and 4. Inheritance of ApoE 4 significantly increases the risk of developing the disease, whereas ApoE 2 protects against it.
- Environmental Factors - other factors have been suggested to contribute to the disease such as exposure to aluminium light, smoking, nutrition and head injuries.