Why is Alzheimer's disease linked to older age?

THAT'S THE WHY:Alzheimer's disease is, for the most part, a condition that we associate with older age. Some people develop symptoms when they are relatively young, but the majority tend to be older. Why is that?

A new paper in the open-access journal PLOS One discusses the possibility that Alzheimer’s disease could be linked with brain cells going into a state of “senescence”, where they no longer divide.

The study measured levels of senescence in the brain with advancing age, and in particular it focused on astrocytes.

These star-shaped cells are the most abundant type of cell in the brain, and they have roles in regulating and maintaining brain function.

The US study looked at brain tissue samples and found that tissue from people aged 78 to 90 had higher levels of senescent astrocytes than tissue from people aged 35 to 50.

Meanwhile, people with Alzheimer’s disease tended to have a greater burden of senescent astrocytes in an area called the frontal cortex compared with people of a similar age who did not have Alzheimer’s disease. Also, the Philadelphia-based researchers found that senescent astrocytes produced inflammatory molecules.

Obviously Alzheimer’s disease is a complex condition and there are many questions yet to answer, but the study authors argue that senescent astrocytes could be a component.

“We propose that the presence of senescent astrocytes contributes to the pathogenesis of AD and may represent a link between the ageing process and progression of the disease,” they write.