Cognitive Stress And Heart Rate Variability

Mental stress is an important factor affecting physical and mental health,and it also has a serious impact on people's daily life and work efficiency.In order to prevent the formation of chronic mental stress and irreversible health damage,it is of great significance to find a real-time and convenient method to assess and detect mental stress.With the development of wearable technology,real-time and non-invasive physiological signal collection and analysis have been available,and which prompts a growing number of researches to pay attention to the feasibility of physiological signals for monitoring and evaluating stress in order to achieve objective measurement of mental stress.On the other hand,mental stress,as the body's response to external changes,is related to the ability of individuals' adjustment to their emotions,cognition and behavioral adaption to changes(i.e.self-regulation).Researches have shown that self-regulation is closely related to individuals'education and career achievement,socioeconomic status and health condition.Therefore,the study of changes of individuals'physiological signals under different stress conditions may explain self-regulation and its effects on the above three important aspects.Heart rate variability(HRV),which contains reliable information about the autonomic nervous system(ANS),has been widely studied as a biomarker of mental stress and self-regulation.Previous researches have shown that some HRV metrics were significantly correlated with mental stress and self-regulation.However,the research methods and results of HRV stress assessment in different laboratories are heterogeneous,and there is no unified conclusion and explanation.In addition,previous experimental studies have found that resting HRV had a significant relationship with self-regulation,but little attention was paid to the relationship between HRV reactivity and self-regulation,and the relationship between HRV and achievement and health was still unknown.This paper attempts to investigate whether the time domain,frequency domain and nonlinear indicators of HRV can reliably track changes in mental stress using the ECG data repeatedly measured of college students under different stress states,and to explore the reasons for the inconsistency between the existing research results.In order to explore the possibility of using HRV to predict long-term outcomes of self-regulation,we further analyzed the relationship between resting HRV indicators and cognitive stress-induced changes in HRV indicators and the average academic performance of the subjects' colleges.In this paper,the mental arithmetic task was used as the stress-induced source,and ECG signals of 36 healthy subjects were repeatedly measured when completing two kinds of difficult mental arithmetic tasks.A total of 28 subjects completed the experiment and obtained high quality ECG data for subsequent analysis.After filtering the ECG signal,the location of R wave was accurately identified by QRS wave detection algorithm,and the R-R interval and instant heart rate data were obtained.(1)Short-term HRV indicators track changes of acute stress.The 42 HRV indicators in each task phase were obtained using time domain,frequency domain and nonlinear methods.Analyze the reliability of repeated measures of HRV indicators and investigate whether HRV indicators can effectively distinguish between different stress levels and track changes in pressure.The results show that the time domain indicators AVNN,RMSSD,SDSD,frequency domain indicators LFnorm,HFnorm,lnHF,HF-Skewness,HF-Kurtosis and nonlinear indicators SD1,SD12,?1 coefficient D,coefficient E can effectively distinguish different stress level.In addition,the eight indicators meet both absolute reliability and relative reliability standards,but these indicators do not effectively distinguish between different stress levels.The above results show that HRV index has good reliability and is not equivalent to its ability to reliably track mental stress changes.On the other hand,the inconsistent results of the HRV used in the stress assessment of each laboratory can be attributed in part to the fact that certain indicators do not effectively distinguish between different stress levels.(2)The relationship between resting HRV and cognitive stress-induced HRV changes and average university grades.Of the 28 valid subjects,26 were from the same undergraduate professional class(76.4%of the total number of 34 people,and the scores of 8 non-revenue subjects were randomly distributed).And the data of these 26 subjects were used in this study.Pearson correlation analysis was used to calculate the correlation between each HRV indicator and the students' undergraduate grade point average(GPA).The results showed that resting HRV indicators LFnorm,,HFnorm,InHF,?1 and GPA were significantly correlated(P<0.05),and the correlation coefficients were-0.54,0.54,0.48 and-0.43,respectively.In addition,the changes in the indicators AVNN,LFnorm,HFnorm,lnHF,D,E and SD12 from ES1 to DS1 were significantly correlated with GPA,and the change magnitude of these indicators was significantly positively correlated with GPA.These results suggested that short-term HRV reflects the intrinsic self-regulation ability of the subject,and which may predict long-term outcomes of self-regulation.