While Alzheimer's is closely associated with abnormal clumps and tangles of proteins damaging neurons inside the brain, their findings suggest the initial trigger for the disease could be an outside intruder slipping through a compromised brain boundary.

A study of two different cancer drugs in mice showed promise for reversing Alzheimer's brain damage. Scientists are hopeful the same happens in human trials.

As well as helping to prevent the disease, researchers say their findings could support healthy brain aging in general.