TABLE I. AGES AND GENDERS OF PARTICIPANTS Gender Age Female Male Total 20-29 72 33 105 30-39 43 80 123 40-49 45 45 90 50-69 22 20 42 Total 182 178 360 Dependence of Heart Rate Variability on Stress Factors of Stress Response Inventory Lizawati Salahuddin, Myeong Gi Jeong, Desok Kim School of Engineering Information and Communication University Daejeon, Korea lizawati, mgjeong, kimdesok@icu.ac.kr Seong-Kyeon Lim 1 , Kim Won 2 , Jong-Min Woo 2 1 Department of Neuropsychiatry and 2 Stress Research Institute, Seoul Paik Hospital Inje University School of Medicine Seoul, Korea healthpsy@naver.comphrenie@dreamwiz.com, menfi@naver.com Abstract—Heart rate variability (HRV) analysis is commonly used as a quantitative marker depicting the activity of autonomic nervous system (ANS) related to mental stress. Stress Response Inventory (SRI) has been devised to score mental and physical symptoms occurred during the past two weeks. SRI is composed of seven stress factors that may influence the status of mental stress levels. In this study, we investigated the relationships of physiological measures and HRV features on ages and stress factors. Physiological measures and HRV features in low (SRI scores: 7.1 ± 4.1, n=225) and high stress group (22.5 ± 7.4, n=135) were compared with age as the covariate (ANCOVA). Age was reconfirmed as a significant factor influencing physiological measures and most of HRV features. Age was also inversely correlated to stress factor scores. Systolic blood pressure, glucose level, and normalized HF were significantly lower, whereas body temperature, LF/HF, and normalized LF were significantly higher in high stress group. Our results showed that stress levels were associated with ages, physiological measures, and HRV features. Keywords-Heart rate variability; autonomic nervous system; physiological measure; stress; Stress Response Inventory I. INTRODUCTION Stress involves alteration in behavior, autonomic function and the secretion of several hormones such as cortisol, corticosterone, and adrenal catecholamines [1]. Higher blood pressure and heart rates during stress reflected the predominance of sympathetic nervous system activity [2]. Mental stress decreased high frequency of heart rate variability (HRV) and increased low frequency of HRV [3]. HRV decreased in subjects with depression, higher hostility and anxiety [4]. Stress increases susceptibility to negative health outcomes [5]. Autonomic nervous system (ANS) contributes to the physiological adaptive process in short durations but may be damaged if the releases of the mediators such as adrenaline from the adrenal medulla are not terminated when they are no longer needed. Numerous stress questionnaires have been used in clinical practice and psychiatric researches such as Perceived Stress Scale (PSS) [6], Life Events and Coping Inventory (LECI) [7], and Stress Response Inventory (SRI) [8]. PSS measures the degree to which situations in one’s life are considered as stressful. A number of questions may be included to scale feelings, thoughts, and current levels of experienced stress during the last month [6]. LECI is composed of 125 life event questions that assess the experience of life stress and 42 questions that ask the use of coping behaviors in 12-14 years old children [7]. Recently, SRI questionnaire has been devised to score mental and physical symptoms occurred during the past two weeks that may influence the status of mental stress levels. SRI consists of 39 items that focus on the emotional, somatic, cognitive, and behavioral stress responses. SRI scores could be categorized into seven stress factors: tension, aggression, somatization, anger, depression, fatigue, and frustration [8]. Both PSS and SRI were designed to measure stress severity in adults. PSS was designed to assess how unpredictable, uncontrollable, and overloaded respondents find their lives. Unlike PSS, SRI assesses the stress severity based on the stress symptoms or the effects of stressors. However, the relationships of ages, stress factors, physiological measures and HRV features have not been investigated thoroughly. In this study, we compared physiological and HRV features in subjects with high and low stress factors to investigate stress- related symptoms and their influence on HRV features. II. METHODS A. Subjects and Data Acquisition during Baseline Stage The experiment was carried out in Department of Neuropsychiatry and Stress Research Institute, Seoul Paik Hospital, Seoul, Korea and Information and Communications This research was supported by the grant from Samsung Electronics, Inc., Suwon, Korea.