Early signs of Alzheimer's disease may be hidden in the way a person speaks, but it's not yet clear which details of our diction are most critical for diagnosis.
A study from 2023 suggests that as we age, how we say something may matter more than what we say. Researchers at the University of Toronto think the pace of everyday speech may be a better indicator of cognitive decline than difficulty finding a word.
Lethologica, also known as 'tip of the tongue' phenomenon, is experienced by young and old alike. But as we grow older, finding the name for things can become more challenging, especially over the age of 60.
To explore why that is, researchers at the University of Toronto asked 125 healthy adults, between the ages of 18 and 90, to describe a scene in detail.
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Next, the participants were shown pictures of everyday objects while listening to audio that was designed to confirm or confuse them.
For instance, if participants were shown a picture of a broom, the audio might say 'groom', which helps them recall the word through rhyme. But on the flip side, the audio might also offer a related word like 'mop', which can lead the brain astray, momentarily.
The faster a person's natural speech in the first task, the more quickly they came up with answers in the second task.
The findings align with the 'processing speed theory', which argues that a general slowdown in cognitive processing lies at the very center of cognitive decline, not a slowdown in memory centers specifically.
"It is clear that older adults are significantly slower than younger adults in completing various cognitive tasks, including word-production tasks such as picture naming, answering questions, or reading written words," explained a team led by University of Toronto psychologist Hsi T. Wei.
"In natural speech, older adults also tend to produce more dysfluencies such as unfilled and filled pauses (e.g., "uh" and "um") in between speech and have a generally slower speech rate."
In a 2024 piece for The Conversation, dementia researcher Claire Lancaster said that the study from Toronto "has opened exciting doors… showing that it's not just what we say but how fast we say it that can reveal cognitive changes."
Recently, some AI algorithms have even been able to predict an Alzheimer's diagnosis with an accuracy of 78.5 percent using speech patterns alone.
Other studies have found that patients with more signs of amyloid plaque in their brain are 1.2 times more likely to show speech-related problems.
Amyloid plaques are a hallmark of Alzheimer's disease.
In 2024, researchers at Stanford University led a study that found longer pauses and slower speech rates were also associated with higher levels of tangled tau proteins, another hallmark of Alzheimer's.
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"This suggests that speech changes reflect development of Alzheimer's disease pathology even in the absence of overt cognitive impairment," the authors of the study concluded.
The groundwork is still being laid, but scientists are getting closer to decoding the nuances of human speech to figure out what our words are saying about our brains.
The 2023 study was published in Aging, Neuropsychology, and Cognition.