Scientists have shown how having a stroke - or even snoring heavily - can increase the risk of developing Alzheimer's disease.
The research could help scientists stop Alzheimer's developing
A Leeds team found a lack of oxygen in the brain, which occurs during strokes or even in heavy snorers, can affect brain cells called astrocytes.
The changes to the cells let glutamate, a neurotransmitter, build up - which could contribute to Alzheimer's.
The Journal of Neuroscience study may help scientists prevent Alzheimer's.
Under normal circumstances astrocytes mop up glutamate in the brain.
However, the Leeds team found a lack of oxygen decreased the expression of proteins required by the cells to carry out this task.
Glutamate is toxic if allowed to build up in high levels, so the accumulation could lead to brain cell death, and eventually to the onset of Alzheimer's.
Lead researcher Professor Chris Peers said the study was important as it suggested why beta amyloid, the protein that builds up in the brains of Alzheimer's patients, is key to the process of triggering disease.
An important link
It is already known that low oxygen can cause astrocytes to increase their production of beta amyloid.
The latest research suggests it may be this increased production of beta amyloid that blocks expression of the proteins needed for astrocytes to mop up excess glutamate.
Professor Peers said: "This is an important factor in what's going on in hypoxic brains.
"Even though the patient may outwardly recover, the hidden cell damage may be irreversible."
"It could even be an issue for people who snore heavily, whose sleep patterns are such that there will be times in the night when their brain is hypoxic - deprived of sufficient oxygen."
Professor Susanne Sorensen, head of research at the Alzheimer's Society, said: "The team examined the role of cells that support neurones in the brain.
"This is exciting because rather than focussing on neurones they looked at processes in the brain, which until now have not be researched in so much detail."
Co-author Dr Hugh Pearson said: "For most forms of Alzheimer's we don't know what the underlying factor that makes people develop it is."
He said that understanding processses that link having the stroke and developing Alzheimer's they could help with the development of treatments to intervene and so decrease the number of Alzheimer's cases.