Down syndrome helps researchers understand Alzheimer's disease

The link between a protein typically associated with Alzheimer's disease and its impact on memory and cognition may not be as clear as once thought, according to a new study from the University of Wisconsin-Madison's Waisman Center. The findings are revealing more information about the earliest stages of the neurodegenerative disease.

The researchers - including lead study author Sigan Hartley, UW-Madison assistant professor of human development and family studies, and Brad Christian, UW-Madison associate professor of medical physics and psychiatry and director of PET Physics in the Waisman Laboratory for Brain Imaging and Behavior - looked at the role of the brain protein amyloid-β in adults living with Down syndrome, a genetic condition that leaves people more susceptible to developing Alzheimer's. They published their findings in the September issue of the journal Brain.

"Our hope is to better understand the role of this protein in memory and cognitive function," says Hartley. "With this information we hope to better understand the earliest stages in the development of this disease and gain information to guide prevention and treatment efforts."

However, the findings of their study not only may help scientists better understand the condition as it impacts those living with Down syndrome, but they are also relevant to adults without the genetic syndrome.

"There are many unanswered questions about at what point amyloid-β, together with other brain changes, begins to take a toll on memory and cognition and why certain individuals may be more resistant than others," says Hartley.

The UW-Madison scientists, along with collaborators at the University of Pittsburgh, studied 63 healthy adults with Down syndrome, aged 30 to 53, who did not exhibit clinical signs of Alzheimer's or other forms of dementia. They found that many adults with Down syndrome had high levels of amyloid-β protein but did not suffer the expected negative consequences of the elevated protein.

About Down Syndrome and Alzheimer's Down syndrome is a condition in which a person is born with extra genetic material from chromosome 21, one of the 23 human chromosomes. Most people with Down syndrome have a full extra copy of chromosome 21, so they have three copies instead of the usual two. In ways that scientists don't yet understand, the extra copies of genes present in Down syndrome cause developmental problems and health issues. Scientists think that the increased risk of dementia in individuals with Down syndrome may also result from the extra gene.

As with all adults, advancing age also increases the chances a person with Down syndrome will develop Alzheimer's disease. Because people with Down syndrome live, on average, 55 to 60 years, they are more likely to develop younger-onset Alzheimer’s (Alzheimer’s occurring before age 65) than
older-onset Alzheimer’s (Alzheimer’s occurring at age 65 or older).