Breath test reveals stress level

Content of six molecules in the exhaled air changes measurably in stressed people

Stress - soon recognizable by the breath? © SXC
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A deep exhalation could be sufficient in future to betray our stress level. Because British researchers have identified six molecules whose content changes in stressed people in the exhaled air. On the basis of these findings, it would be possible to develop a test that recognizes the psychological stress on the basis of these components, as the scientists report in the journal "Breath Research".

For some time now, physicians no longer have to rely solely on blood or urine samples if they want to find evidence of a disease. The telltale signs of an infection or other illness also reach our exhaled air through our lungs. Using chemical detection methods, biomarkers for tuberculosis, various cancers, pneumonia and asthma can already be identified. Whether a physiological state of emergency such as stress manifests itself in our exhaled air was not yet known. Paul Thomas from Loughborough University in Leicestershire and his colleagues have now investigated this question.

Previous stress tests in humans and animals usually determine the concentration of certain stress hormones such as cortisol and require a blood or saliva sample. "If we could objectively measure stress in the future without using any invasive methods, that would be a great help to many sufferers, " explains Thomas. In addition, it would also be possible to determine the psychological burden of patients who are no longer able to provide information about their condition, such as dementia patients.

Breath test after mathestres

For their study, the researchers first took a breath test from their volunteers - 22 young women and men. Then all the participants were exposed to two different situations: In one, they were allowed to sit down relaxed and listen to quiet music, in the other they had to solve mathematical tasks under time pressure - for most of us pure stress. During these sessions, the researchers monitored the volunteers' pulse and blood pressure, and at the end of each session they took another breath sample from each.

All breath samples were analyzed for their ingredients using gas chromatography and compared. The presumption of the researchers: Because stress boosts our metabolism, pulse and blood pressure increase and we breathe faster. This could also change the composition of the gases we exhale. In fact, Thomas and his colleagues identified six chemical compounds in the subjects' breathing air that may be suitable as stress indicators. display

Two substances increased, four reduced

The concentrations for two of the compounds, indole and 2-methylpentadecane, were significantly increased after the stressful math tasks. Four other substances, on the other hand, appeared to be thickened by the increased respiration - their content dropped in the stressed subjects, as the researchers report. They are therefore good starting points for developing a quick test for stress.

However, further tests with larger numbers of participants are needed to confirm their results, they emphasize. "But disease does not seem to be the only factor influencing our exhaled air - it also needs to be taken into account when using such tests for diagnosing disease."

(Institute of Physics (IOP), 01.03.2013 - NPO)