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Development of four stress levels in group stroop colour word test using HRV analysis

Vanitha L, Suresh GR, Chandrasekar M, Punita P

Background: Stress has become an integrated part of our life. Stress was modelled as four stages by Hans Selye’s in his General Adaptation Syndrome (GAS) model. Objective: The main objective of this work is to design an efficient laboratory Group Stroop Colour Word Test (GSCWT) to induce distinct four levels of stress that is, no stress, low, medium and high stress, which mimics a real time working memory (WM) load for the subject and thus cause stress for the subject.

Subjects and Method: Healthy and normal 50 subject’s Heart Rate Variability (HRV) is considered for analysis. GSCWT is developed using software Matlab 2013 and is validated by recording ECG both at rest and while performing the different levels of stroop task. The time domain, frequency domain parameters of HRV is determined using kubios software and the influence of GSCWT between the different levels of stress is analysed using statistical t-test to compare the features between each state and one-way Anova test is used to compare the features between all states. SPSS software is used for statistical analysis.

Results: The results show that, all the HRV parameters are sensitive to WM demands, thus sensitive to stress and are sensitive indicators of different levels of mental stress. The developed GSCWT satisfies the Hans Selye’s GAS model of stress.

Conclusion: The developed GSCWT test significantly differs between the four levels of stress compared to the previously developed Stroop colour test, the feature which makes this test as an efficient tool for conducting laboratory test, which can be used to develop a mental stress level measuring system that can efficiently distinguish between the different stress levels. The test can be conducted even with illiterate subjects as the only requirement of the subject to take up the test is to discriminate colours.