Alzheimer's and the Confounding Arrow of Causation
Back in March we reported on the finding that beta amyloid, which accumulates in the brains of Alzheimer's patients, is a potent antibiotic; thereby generating the hypothesis that its presence wasn't the result of a malfunction but rather was an effect of an immune response to a chronic brain infection. If that's really the case, getting rid of it might not be the way to go.
Today Gina Kolata of the NYTimes is reporting on the dramatic failure of a drug designed to reduce the amount of beta amyloid in the brain. It's not that it didn't reduce beta amyloid; it did. The problem is that it made the subjects' Alzheimer's worse; and the more they took the more their conditions worsened.
None of this proves that the real killer is a chronic fungal infection which is slowed down by beta amyloid but it does prove that when it comes to biomarkers the "which is cause and which effect" trap can ensnare the brightest and the savviest.
