From the article:
“Many scientists have focused their Alzheimer’s disease research on the buildup of toxic amyloid and tau proteins in the brain, but this study and others from my lab show that the problem starts earlier – with leaky blood vessels in the brain,” said Berislav Zlokovic, senior author of the study
Reducing fibrinogen that enters the brain through leaky gatekeeping may be important for preventing decline:
Fibrinogen develops blood clots so wounds can heal. When gatekeeper cells are compromised, an unhealthy amount of fibrinogen slinks into the brain and causes white matter and brain structures, including axons (nerve fibers) and oligodendrocytes (cells that produces myelin), to die.