A Simple Saliva Test Could Reveal Hidden Signs of Sleep Loss

Good sleep is essential for our physical and mental health. And yet, sleep problems are widespread. According to the latest Swiss Health Survey, around one-third of the population report suffering from sleep disorders. Women and young people aged 15 to 39 are particularly affected.

Although sleep loss is widespread, it has not previously been possible to measure it directly and objectively in bodily fluids. A research team from the Institute of Forensic Medicine and the Institute of Pharmacology and Toxicology at UZH has now investigated whether sleep deprivation can be detected through metabolic changes in saliva. “Our study provides the first direct biomarkers of sleep deprivation in saliva under realistic conditions – a milestone for forensic research,” says Thomas Krämer, professor of forensic pharmacology and toxicology at the UZH Institute of Forensic Medicine.

For the study, the researchers examined 20 healthy young men who normally sleep seven to nine hours. The participants completed three experimental conditions in random order: one night without any sleep, four consecutive nights of six hours’ sleep, and a control condition with the usual eight hours of sleep. The team then analyzed participants’ saliva using high-resolution mass spectrometry and employed machine-learning methods to identify molecular patterns associated with acute sleep deprivation.

“We found that acute sleep deprivation affects about 10% of all biomolecules in saliva. The challenge was to identify, among tens of thousands of molecules, those that reliably indicate fatigue. Using state-of-the-art technology, we succeeded in identifying 10 biomarkers that do exactly that,” says first author Michael Scholz. As part of his doctoral research, he investigated in depth how fatigue can be measured in the body.

The project is now entering its next phase. In a large-scale international field study, the patented biomarker set will be validated under realistic conditions. The researchers will investigate whether the method can reliably detect sleep deprivation in a range of everyday situations involving shift work, alcohol, medications and other factors.

In the long term, this research could lead to the development of a rapid test that can be used on-site to objectively detect fatigue. “Such a test could improve road safety and enhance safety in work environments where attention and concentration are critical,” says Scholz.