It’s been known that decreased blood flow in the brain occurs in people with Alzheimer's, and recent studies suggest that brain blood flow deficits are one of the earliest detectable symptoms of dementia. A study has now shown why it occurs: a small percentage of capillaries, the smallest blood vessels in the brain, are blocked by white blood cells stuck to the inside of the capillaries.
Recent research has shown that capilleries are vital for monitoring and directing blood flow around the brain.
(2019). Neutrophil adhesion in brain capillaries reduces cortical blood flow and impairs memory function in Alzheimer’s disease mouse models.
Nature Neuroscience. 22(3), 413 - 420.