What is Alzheimer's Disease in Individuals with Down Syndrome?
Alzheimer's disease (AD) is the most common form of dementia. The disease is progressive, and the brain degenerates. Alzheimer's disease is strongly associated with old age. However, it should not be considered a normal part of aging. Down syndrome (DS) is a genetic disorder (the chromosome abnormality is acquired at the time of conception) in which a person has extra genes because of extra chromosome 21 material. The syndrome causes delays and limitations in physical and intellectual development. The extra chromosome material can be inherited from either parent. Common characteristics of the syndrome include: Low muscle tone Flat face (low nasal bridge and small nose) Eye openings that slant downward and inward Single crease across the centre of the palm Smaller than normal size Delay of both physical and intellectual development
People with Down syndrome, also called trisomy 21, develop a syndrome of dementia that has the same characteristics of Alzheimer's disease that occurs in individuals without Down syndrome. The only difference is that Alzheimer's disease occurs much earlier in people with Down syndrome; patients with Down syndrome begin to have symptoms in their late 40s or early 50s. Most (and maybe all) people with Down syndrome develop the brain changes associated with Alzheimer's disease. However, Alzheimer's disease is not more common in individuals with intellectual disabilities from causes other than Down syndrome. The percent of people with Down syndrome that have Alzheimer's disease increases with age, with a majority occurring in people older than 60. Alzheimer's disease decreases survival in people with Down syndrome who are older than 45 years of age.