Speech rate and word-finding difficulties, including pausing and use of fillers such as “um” and “uh,” were associated with changes in executive function across the adult lifespan in a new study.

The findings suggest that longitudinal analyses of natural speech patterns and processing speed might reveal cognitive decline associated with normal aging or emerging neuropathology, according to study author Jed Meltzer, PhD, associate professor of psychology and speech-language pathology at the University of Toronto, and colleagues.

“If we are going to understand Alzheimer’s and have more sensitive diagnostics, we need to be able to distinguish the changes that happen in the pathological condition vs what we might expect to be an ordinary rate of decline,” Meltzer told Medscape News Canada.

The study was published on November 7 in the Journal of Speech, Language, and Hearing Research.

Beyond Current Screening Tools

Executive function is the set of mental skills that control and direct thought and behavior by supporting the capacity for attention and working memory, planning and organization, self-control, and flexibility. It has long been known to peak in early adulthood and decline with age. 

Common cognitive screening tools, such as the Montreal Cognitive Assessment (MoCA) and Mini-Mental State Examination, have a low sensitivity to executive function decline, Meltzer said.

“MoCA is not timed; there’s no speed component,” he noted. “If you are interested in measuring the ordinary decline that we all go through and also accelerated cognitive decline in people developing dementia, then tests sensitive to speed are more sensitive for showing fine degrees of decline.”

To explore whether links between changes in processing speed and other characteristics of normal speech were related to variability in executive function, Meltzer and his research team conducted two studies using neuropsychological tasks and natural language processing on speech samples.

The first study included 67 healthy older adult participants aged 65-75 years, and the second included 174 healthy participants aged 18-90 years. In both studies, participants provided speech samples by describing pictures. They also completed the MoCA to assess executive function.

The researchers selected and aggregated specific features of speech into language domains known to be associated with clinical stages of Alzheimer’s disease and dementia (eg, word finding, sentence structure, speech rate, and pauses). An artificial intelligence natural learning model was used to identify speech features that would predict executive function test performance after adjustments for age, gender, and education. 

In the first study, older adults’ word-finding difficulties, measured as speech disfluencies such as pausing, showed significant associations with executive function.

The second study showed that timing-related aspects of speech can explain individual differences in executive function not only for adults older than 65 years but also across the adult lifespan.

Because those timing-related aspects of speech are not captured in standardized clinical assessments, tests that are sensitive to processing speed “may ultimately be far more informative about cognitive decline in aging adults, whether that decline reflects normal aging or incipient neuropathology, and measuring the rate of such decline over time using highly repeatable and noninvasive assessments such as natural speech analysis may be the best way to distinguish those trajectories at an early stage,” the authors concluded. 

“The most exciting aspect of this kind of work is the ability to assess people longitudinally for the decline in the natural course of life and assess whether certain interventions help to slow that decline,” said Meltzer. Within the next 5 years or so, he suggested, clinicians will be able to incorporate longitudinal, speed-based speech tests into clinical practice. 

“Cognitive decline, as we are measuring it, is a physical phenomenon,” he added. “There’s something changing in the brain that we want to understand and then figure out how to protect against.”

Cognitive Decline Trajectory

“The idea that we could extract measures that map onto executive function capacity in people who are just speaking” has clinical implications, Vanessa Taler, PhD, professor of psychology at the University of Ottawa and senior investigator at Bruyère Health Research in Ottawa, told Medscape News Canada.

“When we’re looking at new clinical trials, it’s quite useful to be able to identify people that are potentially on the trajectory to cognitive decline or dementia, which is probably the most effective stage for intervention,” said Taler, who was not involved in the study. Additionally, “there’s a benefit in knowing your trajectory, just in terms of planning and preparing.” 

The study was supported by an internship grant from the Mitacs Accelerate program and an NSERC Discovery Grant. Meltzer reported holding stock options in Winterlight Labs. Taler reported having no relevant financial relationships.

Liz Scherer is a health and medical journalist who frequently reports for Medscape Canada and Medscape Europe.