This breakdown was shown to increase in Mild Cognitive Impairment, which sometimes leads to AD.44 Studies have shown blood‐derived toxins to accumulate in postmortem AD,45 and in at least a subset of AD patients histological, radiological, and CSF albumin abnormalities have been reported suggesting BBB impairment.46 If indeed the BBB is disrupted in AD then this could provide a direct route whereby proteins pass from the brain to the bloodstream (or vice versa) in sufficient quantities as to be detectable. This evidence concerns the gene ALB and Cognitive impairment.