Alzheimer's Disease May Be Revealed by How Fast We Speak

Early indications of Alzheimer's disease could be reflected in how someone speaks, although the aspects of speech most important for diagnosis have yet to be established.

Research published in 2023 indicates that, with advancing age, how we speak may be more significant than what we say. Scientists at the University of Toronto propose that the speed of ordinary conversation could be a stronger marker of cognitive decline than struggling to retrieve a particular word.

"Our results indicate that changes in general talking speed may reflect changes in the brain," said cognitive neuroscientist Jed Meltzer when the research was published.

"This suggests that talking speed should be tested as part of standard cognitive assessments to help clinicians detect cognitive decline faster and help older adults support their brain health as they age."

Watch the video below for an overview of the study:

Speech pace and cognitive decline

Lethologica, or the ‘tip of the tongue’ experience, affects both younger and older people. Yet identifying the names of objects may become harder as people age, particularly beyond the age of 60.

To investigate this, the researchers asked 125 healthy adults between 18 and 90 years old to give a detailed description of a scene.

The volunteers then viewed images of common objects while hearing audio intended either to assist or to distract them.

For example, someone shown an image of a broom might hear ‘groom’, a rhyme that can prompt recall of the word. Alternatively, they could hear an associated word such as ‘mop’, which may briefly send the brain in the wrong direction.

People whose spontaneous speech was quicker in the first exercise also found answers faster in the second.

These results support the ‘processing speed theory’, which proposes that cognitive decline is rooted in an overall slowing of cognitive processing rather than specifically in slower memory centres.

"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 article for The Conversation, dementia researcher Claire Lancaster said the Toronto research "has opened exciting doors… showing that it's not just what we say but how fast we say it that can reveal cognitive changes."

Alzheimer's disease proteins and speech patterns

More recently, certain AI algorithms have predicted an Alzheimer's diagnosis from speech patterns with 78.5 percent accuracy.

Separate research has shown that people with more evidence of amyloid plaque in the brain are 1.2 times more likely to experience speech-related difficulties.

Amyloid plaques, alongside tau tangles, are a defining feature of Alzheimer's disease.

In 2024, a Stanford University-led study linked longer pauses and slower rates of speech with higher levels of tangled tau proteins.

Brain-imaging data from 237 cognitively unimpaired adults showed that participants with heavier tau burdens generally spoke more slowly, paused for longer between utterances, and paused more often overall.

Notably, those with stronger evidence of tau in their brains were no more likely to struggle to give the right answer in memory-recall tests.

It may be that people experiencing early memory problems can still reach the correct answer, but need more time to do so, resulting in slower speech and additional pauses.

If so, speech patterns observed during memory-recall tests might offer entirely new information about an individual’s neurological condition that conventional assessments do not capture.

"This suggests that speech changes reflect development of Alzheimer's disease pathology even in the absence of overt cognitive impairment," the authors of the 2023 study conclude.

"It may be especially fruitful to examine speech during delayed recall of a story memory task," the team writes.

Further research into dementia risk

Long-term research must now track people who are slower in memory-recall tests to determine whether they later develop dementia or cognitive difficulties.

After all, evidence of increased tau tangles or amyloid plaques in the brain does not mean a person is certain to develop Alzheimer's.

Although more work remains, scientists are moving nearer to unpicking the subtleties of human speech and understanding what our words may reveal about our brains.

The 2023 study appeared in Aging, Neuropsychology, and Cognition.

An earlier version of this article was published in July 2025.