Alzheimer's disease is the most common form of dementia. It is a terminal illness where a person may eventually suffer with permanent memory loss, language problems, poor cognitive functions and other behavioural changes. The exact cause and progress of the disease is uncertain. But a new study, published in the Journal Brain, indicates that certain signs and risk of developing can be seen at a very young age around your 20's - a much younger age than scientists previously imagined.
A group of researchers have found that amyloid,an abnormal protein whose accumulation in the brain is a hallmark of Alzheimer's disease, starts accumulating inside neurons of young humans brains. Previous studies have already established that amyloid accumulates and forms clumps of plaque outside neurons in ageing adults and in Alzheimer's. The greatest risk factor is age as majority of people with Alzheimer's are usually 65 and older. But this study shows that tt is not just an old age disease, it may affect people at a younger age but the symptoms may become prominent only later.
According to Lead Investigator Changiz Geula from Northwestern University's Feinberg School of Medicine, "Discovering that amyloid begins to accumulate so early in life is unprecedented. This is very significant. We know that amyloid, when present for long periods of time, is bad for you."
For the study, scientists examined basal forebrain cholinergic neurons to try to understand 'why' they are damaged early. These vulnerable neurons are closely involved in memory and attention. Geula and colleagues examined these neurons from the brains of three groups of deceased individuals. Scientists found that amyloid molecules began accumulating inside these neurons in young adulthood and continued throughout the lifespan.
Nerve cells in other areas of the brain did not show the same extent of amyloid accumulation. The amyloid molecules in these cells formed small toxic clumps, amyloid oligomers, which were present even in individuals in their 20's and other normal young individuals.The size of the clumps grew larger in older individuals and those with Alzheimer's. This points to why these neurons die early.
"The small clumps of amyloid may be a key reason. The lifelong accumulation of amyloid in these neurons likely contributes to the vulnerability of these cells to pathology in ageing and loss in Alzheimer's," the authors wrote.
The study showed that this disease may disease may start to attack the brain cells almost half a century before the symptoms develop.
"It is also possible that the clumps get so large, the degradation machinery in the cell cannot get rid of them and they clog it up," Geula noted. These findings may help in developiong tools for the early detection of the disease. The team now plans to investigate 'how' the internal amyloid damages the neurons in future research.