Brains of people with Down syndrome show signs of neuroinflammation and neurodegeneration in the first three years of life, according to research from the Waisman Center at the University of Wisconsin-Madison published in Science. The finding pushes the known start of these processes back by roughly two decades: they had previously been documented in people with Down syndrome in their early 20s.
Down syndrome, caused by an extra copy of chromosome 21, is the most common genetic cause of intellectual disability, and more than 90 percent of people with the condition develop Alzheimer's disease in adulthood. Researchers already knew that inflammation and cell loss precede dementia symptoms by many years. What the new work adds is a much earlier starting point, along with evidence of widespread dysregulation of genes, all occurring while the brain is still actively developing.
That overlap matters. Neuroinflammation is an immune response inside the brain, and when it becomes chronic it can drive neurons to die - a hallmark of Alzheimer's and related diseases. If the same process is already underway during infancy in Down syndrome, then the developmental and degenerative sides of the condition are not separate chapters but intertwined from the start, as the study's authors describe it.
The team frames its results as an atlas of early brain development in Down syndrome, a reference map that could help identify when and where to intervene. Treatments aimed at both the developmental and degenerative features of the condition are the eventual goal, though the study itself describes the biology rather than testing any therapy.