Type D personality related to reduced reactivity of heart rate variability to mental stress among professional firefighters
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With the advancement of research on the etiology of cardiac death, psychological characteristics including type D personality, depression, trait anxiety and hostility gain more and more attention from clinicians and researchers. These psychological characteristics have been consistently found to significantly and independently predict cardiac death not only in cardiac patients but also in generally healthy populations. Among these characteristics, the prognostic value of type D personality even goes beyond standard biological risk factors, such as impaired left ventricular function, three-vessel disease and poor exercise tolerance. The purpose of this program of research is to investigate a possible physiological mechanism linking type D personality and cardiac death. The understanding of the physiological mechanism will provide the foundation for further research and sensitive behavioral, psychosocial and pharmaceutical interventions that could sever the physiological linkage from psychological characteristics to cardiac death. This dissertation consists of three manuscripts. The first manuscript, Laboratory-Induced Mental Stress, Cardiovascular Responses and Individual Characteristics, is a systematic review describing the employed mental stress tests and measured cardiovascular dependent variables in current literature and summarizing the effects of psychological characteristics on cardiovascular responses to mental stress. The second manuscript, entitled Depression and Heart Rate Variability in Firefighters, is a secondary data analysis, which used the electrocardiogram (ECG) data collected in the Surveying & Assessing Firefighter Fitness & Electrocardiograms study. The purpose of the secondary data analysis is to explore the feasibility of using ambulatorily acquired ECG data for heart rate variability analysis, and of using the effect size to calculate the sample size. The third manuscript is the dissertation study, named Type D Personality Related to Reduced Heart Rate Variability Reactivity to Mental Stress among Professional Firefighters. It investigates the effect of type D personality on the activity of cardiac autonomic nervous systems during mental stress.