Aston University wearable sensor spots signs of stress and anxiety

A project led by Aston University has developed a wearable device collecting optical metabolic data as indications of mental health.

Published in Nature Communications Medicine, the findings suggest that wearable optical sensing of microcirculation and tissue metabolism could help objective assessment of stress-related mental health states.

Previous wearable-based measures of mental health have used factors such as heart rate variability to reflect autonomic nervous system activity. But these are indirect markers of psychological states and subject to many confounding factors, commented the project.

"Mental health problems such as stress, anxiety and depression are usually assessed using questionnaires, which rely on how people describe their own feelings," wrote the Aston team in its paper. "We explored whether a wearable device can help measure mental health using physical signals from the body."

The project's solution combines laser Doppler flowmetry (LDF), in which movement of red blood cells alters the frequency of low-power 850-nanometer laser light reflected from tissues as an indication of blood flow; and fluorescence spectroscopy (FS), using a 365-nanometer source to excite autofluorescence from nicotinamide adenine dinucleotide (NADH) enzymes. Fluorescence amplitude is then taken as a marker of the tissue's metabolic characteristics.

For a proof-of-concept trial, 132 adults aged 18 to 94 years from 19 countries were assessed using the device, and the biomarker data were compared with mental health assessments gathered via a standardized 21-item questionnaire. This represents "one of the largest and most systematically characterized datasets integrating LDF and FS signals in psychiatric research," noted the project.

Results showed that the combination of optical measurements and ensemble-based data analysis could distinguish individuals with stress-related symptoms from those without, and did so with what the project characterized as "moderate success." Demographic variables, including sex, age, body mass index, and heart rate, were registered in the data and associated with increased stress-related risk.

Monitor well-being without invasive testing

The researchers say the eventual aim would be to complement, rather than replace, existing mental health assessments, and optical technology does not currently diagnose conditions such as depression or anxiety. Study participants were classified using their answers to a questionnaire, rather than diagnoses made by mental health professionals, with larger studies and independent clinical validation needed to establish its reliability across different populations and everyday environments.

Even so, the project's work has now created a dataset containing physiological measurements from a relatively diverse group of participants, to help other researchers investigate the relationship between mental health, circulation and cellular activity. Aston believes the system could ultimately help people and healthcare professionals monitor changes in well-being without requiring invasive medical tests. 

"This study suggests that non-invasive photonic wearable technology can detect changes in blood flow and tissue activity through the skin, and provide useful information about a person's stress-related symptoms," said Edik Rafailov from the Aston Institute of Photonic Technologies.

“At present, mental health is generally assessed through conversations and questionnaires. These remain extremely important, but in the future physiological measurements could provide an additional source of information and help people monitor changes over time."