Acute mental stress detection via ultra-short term HRV analysis

Acute mental stress reduces working performances and is one of the first causes of cognitive dysfunctions, cardiovascular disorders and depression. Stress detection via short term (5 minutes) Heart Rate Variability (HRV) has been widely investigated in the last years. Recent improvements in wearable sensing devices and mobile computing raised a new research question: is ultra-short (2 minutes) HRV as effective as the short term one to detect mental stress? This study aimed to answer this research question. Short and ultra-short HRV was compared in 42 healthy subjects (age 25-38 years) undertaking the widely adopted and highly-effective the Stroop Color Word Test (CWT). ECG signals were recorded during rest and stress session using a chest wearable monitoring device, the BioHarness M3 (ZephyrTech, NZ). HRV measures were then extracted and analyzed according to the literature and using validated software tools. Variations between short and ultra-short HRV measures in rest and stress sessions were analysed with the statistical Wilcoxon significance test. The results of the current study suggested that 6 HRV measures are effective in detecting acute mental stress both using short and ultra-short term analysis: Mean RR, Low Frequency power, Sample Entropy, Detrended fluctuation analysis: Short term and Long term fluctuation slope and Mean line length of Recurrence plot analysis.