Most of us are able to let other people know that we’re stressed, simply by telling them. For people such as those suffering from Alzheimer’s, however, it can be difficult to express such a thought. That’s why UK scientists at Loughborough University and Imperial College London are developing a new test that can determine someone’s stress levels by analyzing their breath.

In a study involving 10 male and 12 female young adults, test subjects first sat comfortably and listened to soothing classical music, and were then required to perform a Paced Auditory Serial Addition Test (PASAT), an arithmetic test specifically designed to cause psychological stress. The subjects’ blood pressure and heart rate were monitored throughout, plus breath samples were taken before and after each of the two activities.

The chemical content of those samples was analyzed via gas chromatography-mass spectrometry. It was found that the compounds 2-methyl, pentadecane and indole increased with stress, while another four compounds decreased in response to stress.

Although the researchers emphasize that more extensive experimentation is required, their current theory is that the changes in breath content are a result of a faster rate of respiration, increased pulse rate and elevated blood pressure – which are themselves all physiological responses to stress.

It is hoped that ultimately a standard testing procedure can be developed, that will let caregivers know if non-communicative patients are experiencing stress.

A paper on the study was recently published in the Journal of Breath Research.