Alzheimer's may be triggered by 'squeezed' capillaries in the brain

Alzheimer's may be triggered by capillaries in the brain being 'squeezed', research suggests.

Poor blood flow through the vital organ is often an early warning sign someone is suffering from the memory-robbing disorder.

And now scientists have discovered amyloid β protein, which causes the tell-tale plaques in an Alzheimer's patient's brain, constricts blood vessels. 

This constriction could half the brain's blood supply, depriving its cells of oxygen and vital nutrients. 

Researchers hope a drug that blocks amyloid β's ability to constrict capillaries could prevent cognitive decline in Alzheimer's patients.

However, other experts warn 'a cure or effective treatment is still a very long way off'. 

The research was carried out at University College London and led by Dr Ross Nortley, of the department of neuroscience, physiology and pharmacology.

'Our study has, for the first time, identified the underlying mechanism behind the reduction of brain blood flow in Alzheimer's disease,' Dr Nortley said.

'Since reduced blood flow is the first clinically detectable sign of Alzheimer's, our research generates new leads for possible treatments in the early phase of the disease.'

Dementia affects 850,000 people in the UK, of which 62 per cent have Alzheimer's, according to the Alzheimer's Society. 

And in the US, 5.8million people are living with the incurable condition, which is set to rise to nearly 14million by 2050, Alzheimer's Association statistics show.  

Blood flow to the brain can be reduced by more than 40 per cent in Alzheimer's sufferers, the researchers wrote in the journal Science. 

While it has long been known patients have constricted capillaries in their vital organ, research into this was neglected as scientists focused on how amyloid β damages neurones, they add. 

Vascular resistance largely occurs in the brain's capillaries. This describes the resistance blood must overcome to flow through the circulatory system.

This is controlled by brain cells called pericytes, which past studies suggest may be 'out of sync' in dementia sufferers. 

To uncover more about how this occurs, the researchers looked at 'slices' of brain tissue that were collected from 13 living humans during neurosurgery.