What Causes Alzheimer's Disease?

Potential Causes of Late-Onset Alzheimer’s

It is very likely that a combination of genetic, lifestyle and environmental factors contribute to the risk of developing this form of Alzheimer’s disease (AD), which occurs after age 60. The exact causes are not yet known.

• Genetics
  
  There is no single gene mutation that consistently causes late-onset Alzheimer’s. Instead, the late-onset form seems to represent the combined effect of multiple genes, each of which increases the risk a little. The best known of these is the apolipoprotein E gene (ApoE).

• Lifestyle
  
  Researchers are actively exploring how diet, exercise, the management of medical conditions such as diabetes or high blood pressure, and other lifestyle factors contribute to the risk of developing AD.

• Environment
  
  Education level, head injuries, and other environmental influences may also play a role in AD, and scientists are exploring these avenues.

Causes of Familial (Early-Onset) Alzheimer’s

Specific genetic mutations are usually associated with the development of the familial (early-onset) form of the disease. Familial Alzheimer’s disease (FAD) is a rare form of the illness, affecting fewer than five percent of Alzheimer’s patients. All FAD is early-onset, meaning the disease develops before age 60. FAD results from mutations in one or more of at least three genes. If even one of these mutated genes is inherited from a parent, an individual will almost always develop early-onset Alzheimer’s disease.