Scientists discover speech characteristic that predicts cognitive decline

Early signs of Alzheimer’s disease may be hidden in the way a person speaks, but it is still not clear which details of our speech are most important for diagnosis.

A 2023 study suggests that as we age, how We say that some may be more important what we say University of Toronto researchers think that everyday speech speed may be a better indicator of cognitive decline than word-finding difficulty.

“Our results indicate that changes in normal speaking speed may reflect changes in the brain,” cognitive neuroscientist Jed Meltzer said when the research was published.

“This suggests that speech speed should be tested as part of a standard cognitive assessment to help clinicians detect cognitive decline more quickly and support brain health in older adults as they age.”

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Watch the video below for a summary of the study:

Lethologica, also known as the ‘tip of the tongue’ phenomenon, is experienced by young and old alike. But as we get older, finding names for things can become more challenging, especially in our 60s.

To find out why, researchers asked 125 healthy adults aged 18 to 90 to describe a scene in detail.

Then, participants were shown pictures of everyday objects while listening to audio that was designed to either confirm or confuse them.

For example, if participants are shown a picture of a broom, the audio might say ‘groom’, helping them remember the word through the rhyme. But on the flip side, audio can also offer a related word like ‘mop’, which can trick the brain momentarily.

The faster a person’s natural speech is in the first task, the faster they come up with answers in the second task.

The findings are consistent with the ‘processing speed theory’, which argues that general slowness in cognitive processing is at the heart of cognitive decline, not specifically slowing down memory centers.

“It is clear that older adults are significantly slower than younger adults in completing various cognitive tasks, such as word-production tasks such as naming pictures, answering questions, or reading written words,” explained the team led by University of Toronto psychologist Hsi T. Wei.

“In natural speech, older adults also produce more discontinuities such as incomplete and filled pauses between utterances (eg, “uh” and “um”) and generally have a slower speech rate.”

In a 2024 piece for conversationDementia researcher Clare Lancaster said the Toronto study “opened exciting doors… not just what we say but how fast we speak that can reveal cognitive changes.”

Recently, some AI algorithms have used speech patterns to predict an Alzheimer’s diagnosis with an accuracy of 78.5 percent.

Other studies have found that patients with more signs of amyloid plaque in their brains are 1.2 times more likely to show speech-related problems.

Amyloid plaques are a hallmark of Alzheimer’s disease, as are tau tangles.

In 2024, researchers at Stanford University led a study that found that longer pauses and slower speech rates were associated with higher levels of tangled tau protein.

Neuroimaging records of 237 cognitively impaired adults suggest that those with greater tau burden have slower speech speed, longer pauses between utterances, and more pauses overall.

Interestingly, participants with greater evidence in their heads had no more difficulty producing correct answers on memory recall tests.

Perhaps participants dealing with early memory problems are still searching for the correct answer; They are taking longer to get there, which slows down the speech with more pauses.

If this is true, speech patterns during memory recall tests could provide whole new intel on a person’s neurological state, not captured by traditional tests.

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“This suggests that speech changes reflect the development of the pathology of Alzheimer’s disease even in the absence of obvious cognitive impairment,” the authors of the 2023 study concluded.

“Examining speech during the delayed recall of a narrative memory task may be particularly fruitful,” the team writes.

Longer-term studies are needed to follow up with participants who perform more slowly on memory recall tests, to see if they actually go on to develop dementia or cognitive problems down the road.

After all, just because someone shows signs of tau tangles or amyloid plaques in their brain, doesn’t mean they’re doomed to develop Alzheimer’s.

While there is still work to be done, scientists are getting closer to decoding the subtleties of human speech to discover what our words are saying about our brains.

The study was published in 2023 Aging, neuropsychology, and cognition.

A previous version of this article was published in July 2025.

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