If you’re like many people today, you regularly listen to a podcast series or an audiobook.

Let me ask you, after you’ve finished listening to the story, how much of it do you remember?

If you recall the last chapters but struggle to remember the first ones, watch out! According to a ground-breaking new study, this kind of memory lapse could be an early indicator of future dementia.

Scientists Discover How Delayed Recall Influences Memory

Back in the 1960s researchers discovered that when a list of words is read to cognitively healthy adults, these folks can better recall words at the beginning and end of the list than words in the middle of the list.

On the other hand, Alzheimer’s patients show a greater tendency to forget words read early in the list. What’s more, the same holds true for people diagnosed with Mild Cognitive Impairment (MCI), a condition that often precedes Alzheimer’s. The only difference is that Alzheimer’s patients forget a greater number of words than people suffering with MCI.

Therefore, how well people remember the first words read to them from a list is seen as a useful early predictor of future cognitive decline. This becomes even more accurate when subjects have to wait 15 to 20 minutes before being asked to repeat the list.

Today, tests like these are often used by doctors during routine physical exams to assess memory health, and chances are, you’ve taken one yourself. I took a delayed recall test some years ago to qualify for an insurance policy.

The reason they’re so effective is that research suggests Alzheimer’s pathology originates in the hippocampus, and it’s this area of the brain that turns short-term memories into long term ones.

Delayed Recall in Forming Other Kinds of Memories

Memory researchers wanted to take the investigation into delayed recall one step further to see if the same challenges faced by some folks in recounting words from a list would hold true when they were asked to listen to and recount a story.

“Not all memory is the same,” explained psychologist Davide Bruno.

“Remembering a story may be easier than remembering items on a list because a story benefits from a coherent structure. And so we were not sure whether the order in which information was learned would still have an effect in memory when recalling a story.”

Dr. Bruno and his team designed a two-part study to examine memory performance in a sample of 653 people who listened to a short story. The researchers wanted to see whether it was easier to remember the first part of a short story than the middle part. They found that for cognitively healthy people, as with lists, that it was.

The results of the second part of the study were far more surprising.

Greater Amyloid in Those Who Forget the Start of a Story

For this phase of the study, researchers took a sub-sample of 223 people for whom they had long-term data and who were cognitively healthy when enrolled.

They wanted to find out, by observing brain scans, how many of the volunteers had amyloid beta plaques and whether this was linked to how well they remembered the start of two stories, when comparing immediate and delayed recall.

After controlling for known risk factors for Alzheimer’s and genetic variants that increase the risk of the disease, they found the level of forgetfulness between immediate and delayed recall in the first third of the story was linked to higher levels of amyloid plaque in the brain. Their research was the first ever to demonstrate this in people.

“Presence of amyloid plaques in the brain is hypothesized to kick-start neurodegeneration in Alzheimer’s disease,” explained Dr. Bruno.

“While we are not sure exactly why, forgetting what we learn at the beginning tells us that Alzheimer’s pathology may be settling in. We think it may be related to preserving information about the order of events — a fundamental feature of memory — the loss of which is somewhat akin to a canary in a coal mine, so to speak.”

Dr. Bruno believes their findings are important and should be applied in routine dementia screening because an easy, inexpensive and accurate method of identifying dementia at an early stage, before symptoms show up, is urgently needed.

Longtime readers know there are serious doubts about the importance of amyloid plaques in the development of Alzheimer’s. Even so, there is a correlation between plaques and cognitive loss – the plaques aren’t a sign of health, that’s for sure! – so this delayed recall study does have value in pointing us toward a tool for early diagnosis.

  1. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7031843/ 
  2. https://pubmed.ncbi.nlm.nih.gov/33274833/ 
  3. https://www.ljmu.ac.uk/about-us/news/articles/2020/12/14/forgetting-the-beginning-of-a-story-might-be-early-sign-of-dementia