Take a deep breath for stress test

Older woman breathing deeply
Once we can distinguish between the effects of extreme physical stress and emotional stress, the study needs to be repeated with more people; it will be necessary to recreate the findings with a sample of 500 or so participants.
Professor Paul Thomas
Six molecular markers in the breath could be used to test for – or rule out – stress according to the results of a pilot study which has appeared in IOP Publishing’s Journal of Breath Research this week.

The physiological symptoms perhaps most commonly associated with stress include hyperventilation, shallow breathing, faster pulse rate and elevated blood pressure, but a multidisciplinary team of researchers from Loughborough University and Imperial College London have brought many different skills together to analyse – among other things – the chemical footprint of stress in breath.

In an interview with ScienceOmega.com, lead author of the study and head of Loughborough’s Chemistry Department Professor Paul Thomas spoke about the usefulness of developing a quick and simple method of stress detection and the further work that will be needed to make this a reality.

"Our current area of research is developing point-of-care tests for chronic diseases, and one of the candidate technologies for that purpose is breath testing," Professor Thomas explained. "At the moment, collecting breath samples takes place in the clinic, but quite often people there are waiting to receive bad news and are stressed.

"The primary motivation of the study was to identify if there were any components in breath that we could associate with stress, therefore allowing us to rule out stress as a confounding factor in diagnostics."

A straightforward, non-invasive test to assess someone’s stress levels could prove useful for the many, often vulnerable, people who find it difficult to talk about their emotional state – people with dementia, for example. There are other potential applications such as objectively measuring stress in people in high-pressure roles, but clinicians must be careful if other health and environmental factors are not to confound the results and identify a stress-related marker as a possible disease-related marker or vice versa.

The volunteers taking part in the study participated in two separate sessions. On the first occasion they sat comfortably and listened to non-stressful music, while on the second they were required to complete a mental arithmetic test specifically designed to cause stress. Their heart rate and blood pressure was measured throughout each session, and breath tests were taken before and afterwards.

Gas chromatography-mass spectrometry was used to capture the contents of the breath samples, which were then analysed and compared to a library of compounds. There were six compounds in total that the team identified as potential markers of stress, two of which were present at elevated levels when the subject was stressed and four of which decreased with stress.

"The levels of some compounds may change just because of ventilation," Professor Thomas pointed out. "If your breathing pattern is altered molecules in your system will be released in the breath at different rates, and their concentration might change."

Alternatively, molecules may be present which are the breakdown products of metabolised stress hormones – showing up as an elevated component of the breath. As Professor Thomas explained, reactive oxidative stress responses may also be produced in people undergoing stress, resulting in some evidence of inflammation and protection against inflammation.

"In our work, we found increased levels of a methylated hydrocarbon – 2-methyl-pentadecane – which is a sign of reactive oxidative stress, and we also found an increase in indole," he said. "Indole is present in many blood samples, but it is a breakdown product of serotonin, which is released by the body in response to stress."

22 young adults took part in the research – 10 males and 12 females – and so a key step in potentially developing a test for diagnostic use will be repeating the results in normal settings and across a wide age range, Professor Thomas emphasised. He and his colleagues will also need to combine these findings with those from other profiles – of skin and saliva – their studies of which are yet to be published.

"Then we have to look at the effects of extreme physical stress so that we’re able to exclude that from our study results," he went on. "Once we can distinguish between the effects of extreme physical stress and emotional stress, the study needs to be repeated with more people; it will be necessary to recreate the findings with a sample of 500 or so participants."

In the meantime, Professor Thomas and his colleagues have work in progress on childhood asthma, and other work looking at severe asthma. Another topic they are keenly interested in exploring is the effect of swimming on health – but not in the way you might think.

"Most people’s experience of swimming – which is a great way of taking exercise and staying healthy – is that they receive eye injury," Professor Thomas told me. "Everyone has been to the swimming pool and come back with sore eyes. We’re very interested in looking at what effect that has on the lungs, which are just as delicate as the eyes."


Please click here to access the full research paper.

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