The exact causes of Alzheimer’s disease aren’t fully understood, yet they are not infectious.
Research has shown that the same risk factors associated with heart disease may also increase the risk of Alzheimer’s disease.
Scientists believe that for most people, Alzheimer’s disease is caused by a combination of genetic, lifestyle and environmental factors that affect the brain over time.
Less than 1% of the time, Alzheimer’s is caused by specific genetic changes that virtually guarantee a person will develop the disease. These rare occurrences usually result in disease onset in middle age.
The damage most often starts in the region of the brain that controls memory, but the process begins years before the first symptoms.
The loss of neurons spreads in a somewhat predictable pattern to other regions of the brains. By the late stage of the disease, the brain has shrunk significantly.
So far, scientists have identified rare changes (mutations) in three genes that virtually guarantee a person who inherits one of them will develop Alzheimer’s. But these mutations account for less than 1% of people with Alzheimer’s disease.
Many people with Down syndrome develop Alzheimer’s disease. In fact, signs and symptoms of Alzheimer’s tend to appear 10 to 20 years earlier in people with Down syndrome than they do for the general population.
People who’ve had a severe head trauma have a greater risk of Alzheimer’s disease.
Several large studies found that in people age 50 years or older who had a traumatic brain injury (TBI), the risk of dementia and Alzheimer’s disease increased.
However, it needs to be spelt out that Alzheimer’s disease is not contractable by kiss or intercourse.
