Leukocyte responsiveness, a quantitative assay for subjective mental workload

Assessing psychological stress and mental workload within work-based scenarios relies heavily upon qualitative, subjective, self-assessment techniques, many of which were originally intended for identifying specific pathological disorders and have reduced sensitivity when evaluating everyday stressors. Quantitative measures involve monitoring changes in the cardiopulmonary system and stress hormone concentration. Although these (e.g. heart rate and blood pressure) provide a basic, reactive indication of the presence of a psychological stressor, many are subject to influence by other bio-mechanisms, or are unable to provide rapid results due to complex laboratory analysis. This study demonstrates how immune responsiveness, known to be influenced by psychological stress, can be used to assess changes in mental workload. Healthy male and female subjects (aged between 26 and 55 years) provided capillary blood samples before and after completing the same, basic, driver-related tasks followed by a simple manoeuvre in two unfamiliar motor vehicles. Using a chemiluminescent technique termed Leukocyte Coping Capacity (LCC), the ability of leukocytes to produce reactive oxygen species in vitro was assessed. Significant post-stressor changes in leukocyte activity were demonstrated between treatment groups. These findings add weight to the proposition that leukocyte activation is a useful quantitative measure of psychological stress and mental loading in humans. This study demonstrates the diagnostic ability of LCC for use during ergonomic evaluation, however the potential industrial applications for this technique are numerous and diverse.Relevance to IndustryThis study demonstrates how an aspect of the innate immune response can be used as an objective, diagnostic measure of altered mental workload. In this instance the technique was used during ergonomic evaluation, however any system involving interaction with humans could be optimised using this method.

► Immune responsiveness was used to objectively assess changes in mental workload.
► Subjects performed the same driver-related tasks and manoeuvre in two motor vehicles.
► Significant post-stressor changes in immune activity were shown between treatment groups.