Saturday, October 19, 2024

Alzheimer's disease advances in two phases? Yeah, we knew that.

If you read Beating the Dementia Monster, you know that there are five stages in the advance of Alzheimer's disease.  We said that the first stage, the preclinical stage, may last 15 to 20 years.  In that stage, there are no symptoms and no reason to believe there's a problem.  The disease progresses silently until it hits a "tipping point" when there is a sudden spread of beta amyloid throughout the brain.  This begins the "prodromal" stage producing the symptoms we call mild cognitive impairment.

Here's an article on this from 2019. 

The prodromal stage is when you begin to notice that something isn't right.  Yes, you're older, and older people have trouble with memory and cognition.  But this is different.  You are experiencing more serious problems than your peers.  What you don't realize is that things have already been going wrong for a long time.

If you've been watching the news, you may have seen a stir over new research about two stages of Alzheimer's disease.  For the news story, the two stages are simply the preclinical stage with no symptoms and the other four stages with symptoms taken together.   In popular media, the big takeaway of the story is that there is this preclinical period when the disease is at work, but there are no symptoms.  But this isn't news.  

The research was published in Nature Neuroscience.

I know from experience that a lot of people don't know about the preclinical phase, especially how long it lasts.  So that's what made the story newsworthy.  What's special to the science about this research is that if focuses on what's going on in one part of the brain, the middle temporal gyrus.  This is an area important to memory, language, and vision.  

A gyrus is one of those irregular ridges that you see all over the brain.  Those ridges have names and specific purposes.  And they are the same from one person to another.  If you set my brain down next to the brain of my wife, they would look the same.  (But don't try that.)  Except the brain of Albert Einstein looked a lot different from the brains of the rest of us.  His gyri (or gyruses, depending on your dictionary) were all different from everyone else.

What was the real contribution of this research?  It was to more clearly identify some of the processes occurring as the disease progresses, and it changed our understanding of which cells are being affected.  There's more to explain about that, but it's beyond the scope of this blog.  But you can read about it here if you're interested.

The research was conducted in Seattle by a collaboration of the University of Washington Alzheimer's Disease Research Center and the Allen Institute for Brain Science.  (As someone who is a regular at the UW ADRC, I recognized a name or names among the researchers listed as contributors in the published report.)

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