title: Heart rate complexity: A novel approach to assessing cardiac stress reactivity.
abstract: Correlation dimension (D2), a measure of heart rate (HR) complexity, has been shown to decrease in response to acute mental stress and relate to adverse cardiovascular health. However, the relationship between stress-induced changes in D2 and HR has yet to be established. The present studies aimed to assess this relationship systematically while controlling for changes in respiration and autonomic activity. In Study 1 (N = 25) D2 decreased during stress and predicted HR reactivity even after adjusting for changes in respiration rate, and cardiac vagal tone. This result was replicated in Study 2 (N = 162) and extended by including a measure of cardiac sympathetic activity; correlation dimension remained an independent predictor of HR reactivity in a hierarchical linear model containing measures of cardiac parasympathetic and sympathetic activity and their interaction. These results suggest that correlation dimension may provide additional information regarding cardiac stress reactivity above that provided by traditional measures of cardiac autonomic function.
authors.affiliation: School of Sport, Exercise, and Rehabilitation Sciences, University of Birmingham, Birmingham, UK.
authors.forename: Ryan C
authors.initials: RC
authors.lastname: Brindle
authors.affiliation: Department of Psychiatry, School of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, USA.
authors.forename: Annie T
authors.initials: AT
authors.lastname: Ginty
authors.affiliation: School of Sport, Exercise, and Rehabilitation Sciences, University of Birmingham, Birmingham, UK.
authors.forename: Anna C
authors.initials: AC
authors.lastname: Phillips
authors.affiliation: School of Sport, Exercise, and Rehabilitation Sciences, University of Birmingham, Birmingham, UK.
authors.forename: James P
authors.initials: JP
authors.lastname: Fisher
authors.affiliation: School of Sport, Exercise, and Rehabilitation Sciences, University of Birmingham, Birmingham, UK.
authors.forename: David
authors.initials: D
authors.lastname: McIntyre
authors.affiliation: School of Sport, Exercise, and Rehabilitation Sciences, University of Birmingham, Birmingham, UK.
authors.forename: Douglas
authors.initials: D
authors.lastname: Carroll
mesh_terms: D000293:Adolescent; D001341:Autonomic Nervous System / Q000502:physiology*; D004562:Electrocardiography; D005260:Female; D006321:Heart / Q000502:physiology; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008297:Male; D056152:Respiratory Rate / Q000502:physiology; D013312:Stress, Physiological / Q000502:physiology*; D013315:Stress, Psychological / Q000503:physiopathology*; D014630:Vagus Nerve / Q000502:physiology; D055815:Young Adult
keywords: Correlation dimension; Heart rate; Heart rate variability; Preejection period; Stress