Signs of Alzheimer's disease can be found in people as young as 20, new research has revealed.
Scientists at Northwestern University, Chicago, have found amyloid protein, which accumulates in the brain and leads to neurodegeneration, can be present in individuals as early as half a century before symptoms develop.
While it has been known for a long time that the abnormal protein accumulates and forms clumps of plaque outside neurons in aging adults and in Alzheimer's patients, this is believed to be the first time its accumulation has been witnessed in such young brains.
"Discovering that amyloid begins to accumulate so early in life is unprecedented," said lead investigator Changiz Geula, research professor at the Cognitive Neurology and Alzheimer's Disease Center at Northwestern University Feinberg School of Medicine.
"This is very significant. We know that amyloid, when present for long periods of time, is bad for you."
The researchers examined basal forebrain cholinergic neurons, which are closely involved in memory and attention, to try to understand why they are damaged early and are among the first to die in normal aging and in Alzheimer's.
Three groups of deceased individuals were studied: 13 cognitively normal young individuals, aged between 20 and 66, 16 non-demented old individuals, aged between 70 and 99, and 21 individuals with Alzheimer's aged between 60 and 95.
It was discovered that amyloid molecules began accumulating inside these neurons in young adulthood and continued throughout the lifespan - although other areas of the brain did not experience the same levels of accumulation.
Amyloid oligomers - toxic clumps of amyloid molecules - were found in individuals in their 20s and other normal young people. They were larger in older individuals and those with Alzheimer's.
The researchers stated that the growing clumps probably damage and eventually kill the neurons. When neurons are exposed to these clumps, they trigger an excess of calcium leaking into the cell, which can lead to their death.
Dr Laura Phipps of Alzheimer's Research UK said the study could open up new avenues for research into how amyloid affects the brain throughout life.
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