For years they were flukes of the Alzheimer’s world: elderly people who died at an advanced age and, according to postmortem examinations, with brains chock-full of amyloid plaques and tau tangles, the protein fragments whose presence in the brain is the hallmark of the disease. Yet these brains were off-script. Although Alzheimer’s orthodoxy says these sticky protein clumps between and inside nerve cells destroy synapses and kill neurons, causing memory loss and cognitive decline, these individuals thought and remembered as well as their amyloid- and tau-free peers.
Because so few people donate their brain to science, it was never certain how many died with the hallmark of Alzheimer’s but never developed the disease. And there were always suspicions that maybe these seemingly resilient people did have at least mild Alzheimer’s, or would have developed it eventually; since they were no longer alive to test and track, that couldn’t be ruled out.