Alzheimer Disease (cont.)

We do not know exactly what causes Alzheimer's disease. There is probably not one single cause, but a number of factors that come together in certain people to cause the disease.

• Most experts believe that Alzheimer's disease is not a normal part of aging.
  
  
• While age is a risk factor for the disease, age alone does not seem to cause it.
  
  
• Family history is another risk factor. The disease does seem to run in some families. However, fewer than 10% of cases of Alzheimer's disease are familial. Familial Alzheimer's disease often occurs at a younger age, between ages 30 and 60 years. This is called early-onset familial Alzheimer's disease.

At least 3 different genes have been linked to Alzheimer's disease.

• The one we know the most about controls production of a protein called apolipoprotein E (apoE), which helps in distribution of cholesterol through the body.
  
  
• Everyone has one of the 3 forms of the apoE gene. While one form seems to protect from AD, another form seems to increase the risk of developing the disease.
  
  
• The other genes-apart from ApoE-are known to be mutated in some people with the disease. These actually cause the disease in a few rare cases.
  
  
• Probably there are other genes that contribute to Alzheimer's disease, but we haven't found them yet.

Much of the research in Alzheimer's disease has focused on why and how some people develop deposits of the abnormal protein in their brains. Once the process is understood, it may be possible to develop treatments that stop or prevent it.