Saliva test can reveal dangerous sleep deprivation — Study

A simple saliva test could one day help detect dangerous sleep deprivation in drivers and others whose alertness is critical, according to new research published in the Journal of Proteome Research.

Scientists identified molecular changes in saliva after people went without sleep for 24 hours and used these changes to develop a predictive model that correctly identified sleep-deprived individuals 94 per cent of the time.

Sleep loss can impair alertness, coordination and reaction time, producing effects comparable to severe intoxication. Yet there is currently no clinical test for determining when someone is dangerously sleep-deprived.

Drowsy driving contributes to tens of thousands of crashes in the United States each year, prompting some states to introduce laws aimed at deterring tired drivers.

Thomas Kraemer and colleagues investigated whether sleep deprivation produces measurable changes in saliva that could eventually be used to develop a rapid test suitable for settings ranging from roadside checks to clinical environments.

“Until now, sleep deprivation has been impossible to measure biochemically—and yet it is one of the greatest burdens of our time,” said Kraemer, the study’s corresponding author. “This study introduces the first direct biomarkers of sleep loss in saliva under real-world conditions, marking a milestone in forensic investigations.”

The researchers studied 20 healthy young men who normally slept seven to nine hours each night.

Each participant completed three sleep conditions in random order, with a week between each: one night without sleep, four nights with two fewer hours of sleep than usual, and a well-rested condition involving about eight hours of sleep.

Saliva samples were collected before and after each condition and analysed for changes in metabolites, small molecules produced during the body’s metabolic processes.

The researchers identified 10 molecular differences between samples collected after complete sleep deprivation and those from well-rested participants.

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However, there was no significant metabolic difference between the sleep-restricted and well-rested states. This suggests that losing two hours of sleep per night for four nights may trigger a different biological response from staying awake for an entire night.

Using the altered metabolites, the researchers developed a predictive model to distinguish sleep-deprived individuals from those who were rested. The model correctly identified sleep-deprived samples 94 per cent of the time.

The researchers said the errors may reflect differences in how individuals metabolically recover from sleep loss. Some participants, for example, had not returned to a fully rested metabolic profile after 24 hours of wakefulness followed by eight hours of sleep.

This suggests that eight hours of recovery sleep may not be sufficient for everyone to fully restore their biological state.

The findings point to a potential “sleepiness fingerprint” in saliva that could eventually provide an objective way to detect sleep deprivation.

Kraemer said the team is now conducting a larger international assessment involving more than 1,000 saliva samples from shift workers, women and frequent drivers to determine how well the predictive model performs across different populations.