Your blood could tell if you're too tired to hit the road

Preventing sleep debt is an issue for road safety and certain risky professions. However, only 15% of the adult population achieves the recommendations of 7 to 9 hours of sleep at least five nights a week, reveals a study published in February in the journal Sleep Health. Hence the interest aroused by the recent work of Australian researchers: they have managed to identify molecules characteristic of a significant lack of sleep in the blood of the people concerned.

For this study published in Science Advances, 23 healthy young adults with a regular sleep schedule were involved. The volunteers gave of themselves: 40 hours of continuous wakefulness, followed by an 8-hour sleep phase. Every two hours during the waking phase, they had their blood taken. In these samples, the researchers were interested in blood metabolites, these molecules resulting from the activity of the body's cells whose concentrations are known to vary depending on the fatigue of the individual. Five molecules, including vanillin 4-sulfate and indole 3-propionate, were found to be 99.2% reliable in reporting 24-hour sleep deprivation.

Apart from blood metabolites, other physiological parameters can indicate a lack of sleep such as pupil stability, slow blinking of the eyes or even the presence of microsleeps. But “physiological methods only work up to a certain point,” explains Patrick Lévy, professor of pulmonology specializing in sleep apnea at Grenoble University Hospital. “The metabolites [studied by the Australian team] could clarify the diagnosis of sleep debt, particularly in people suffering from chronic sleep disorders, or in situations where alertness is critical.” These metabolites could, for example, be used to test people who take risky positions in a nuclear power plant, he imagines.

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The road sector could also benefit from progress in this area. Drowsiness is one of the leading causes of fatal accidents among professional drivers on the highway, according to the National Road Safety Council. Indeed, “the consequences of sleep debt are multiple, the most visible are manifested on brain functioning with a reduction in cognitive abilities, attention and an increase in response time,” explains Professor Lévy. Studies reveal that driving after a sleepless night is equivalent to hitting the road with a blood alcohol level of 0.9 g/L, which is beyond legality. Professor Damien Léger, president of the scientific council of the national institute of sleep and vigilance, reports on the road safety site that "at the first signs of drowsiness, the driver must stop because the risks of having an accident in the following half hour are multiplied by 3 or 4”.

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Although the prospects are interesting, the research remains preliminary and it is not tomorrow that we will be offered a molecular test for sleep debt in the breathalyzer style. “Given that it is blood, the test is not very usable in a road context,” explains Katerine Jeppe, who led the study. However, future work could examine whether our metabolites, and therefore biomarkers, are detectable in saliva or in exhaled air.