Down syndrome increases the risk of Alzheimer’s disease. People with Down syndrome may experience health problems as they age that are similar to those experienced by older people in the general population. The presence of extra genetic material found among persons with Down syndrome may lead to abnormalities in the immune system and a higher susceptibility to certain illnesses, such as Alzheimer's, leukemia, seizures, cataracts, breathing problems, and heart conditions.
People with Down syndrome also experience premature aging. That is, they show physical changes related to aging about 20 to 30 years ahead of people of the same age in the general population. As a result, Alzheimer's disease is far more common in people with Down syndrome than in the regular population. Adults with Down syndrome often are in their mid to late 40s or early 50s when Alzheimer's symptoms first appear. People in the general population don't usually experience symptoms until they are in their late 60s.
The symptoms of Alzheimer's disease may be expressed differently among adults with Down syndrome. For example, in the early stages of the disease, memory loss is not always noted. In addition, not all symptoms ordinarily associated with Alzheimer's disease will occur. Generally, changes in activities of daily living skills are noted, and the person with Down syndrome may begin to have seizures when they never had them before. Changes in mental processes -- such as thinking, reasoning, and judgment -- also may be present, but they often are not commonly noticeable because of limitation of the individual's functioning in general.
How Common Is Alzheimer's Disease in People With Down Syndrome?
Estimates suggest that 25% or more of individuals with Down syndrome over age 35 show the signs and symptoms of Alzheimer's-type dementia. The percentage increases with age. The incidence of Alzheimer's disease in people with Down syndrome is estimated to be three to five times greater than that of the general population.
Why Do People With Down Syndrome Get Alzheimer's Disease?
Current research shows that the extra "gene dosage" caused by the abnormal third chromosome of Down syndrome may be a factor in the development of Alzheimer's disease. The early aging of the Down syndrome brain may also be a factor.