As I approached the arena to cheer on the area college basketball team on Sunday, I met my friend Sondra and her son, Q. As I approached, Q (who has Down syndrome) ran and gave me a big hug. We went to our seats and enjoyed the action. During one of the timeouts, I had a chance to ask Sondra a question that had been hovering in the back of my mind since earlier that day when I read a news story about Alzheimer’s disease. “Sondra, what do you know about the link between Down syndrome and Alzheimer’s?” I asked.
It turns out that there is quite a link. As HealthCentral expert Christine Kennard noted in a 2008 sharepost, researchers have only recently identified the link between Down syndrome and Alzheimer’s. “The main reason for not previously recognizing DS as a significant risk factor for Alzheimer's is life expectancy. In the 1920s, life expectancy for people with DS was just 9 years. This increased to 12 years by 1949 and 35 years of age by 1985,” Christine wrote. “Now, people with DS, live an average of 55 years or more. However, their increased life span has increased their susceptibility to conditions of aging.”
And researchers now believe that people with Down syndrome are more susceptible to Alzheimer’s. “Estimates vary, but a reasonable conclusion is that 25 percent or more of individuals with Down syndrome over age 35 show clinical signs and symptoms of Alzheimer's-type dementia,” the National Down Syndrome Society’s website reports. “The percentage increases with age. In the general population, Alzheimer's disease does not usually develop before age 50, and the highest incidence (in people over age 65) is between five and 10 percent. The incidence of Alzheimer's disease in the Down syndrome population is estimated to be three to five times greater than in the general population, and oftentimes, symptoms begin much earlier.”
Some researchers are studying whether there is a genetic predisposition based on Chromosome 21. Christine’s sharepost also mentioned that researchers believed that the brains of people with Down syndrome have increased levels of B-amyloid (which also are believed to be a major contributor to Alzheimer’s).
In fact, a 2010 study found that amyloid beta can accumulate in the eyes of people with Down syndrome, causing cataracts. "We have known that these cataracts are prevalent in people with Down syndrome and are sometimes seen at birth, but we never knew how they were related to the disorder” Dr. David G. Hunter, ophthalmologist-in-chief at Children's Hospital Boston and vice chairman of the department of ophthalmology at Harvard Medical School told HealthDay News. “Now we know. These distinctive cataracts appear only in people with advanced Alzheimer's disease and much earlier in Down syndrome." The researchers hope to develop an eye test that can be used to identify early signs of Alzheimer’s disease.