title: Sleep variability and cardiac autonomic modulation in adolescents - Penn State Child Cohort (PSCC) study.
abstract: OBJECTIVE
  To investigate the effects of objectively measured habitual sleep patterns on cardiac autonomic modulation (CAM) in a population-based sample of adolescents.
  
  
  METHODS
  We used data from 421 adolescents who completed the follow-up examination in the Penn State Children Cohort study. CAM was assessed by heart rate (HR) variability (HRV) analysis of beat-to-beat normal R-R intervals from a 39-h electrocardiogram, on a 30-min basis. The HRV indices included frequency domain (HF, LF, and LF/HF ratio), and time domain (SDNN, RMSSD, and heart rate or HR) variables. Actigraphy was used for seven consecutive nights to estimate nightly sleep duration and time in bed. The seven-night mean (SD) of sleep duration and sleep efficiency were used to represent sleep duration, duration variability, sleep efficiency, and efficiency variability, respectively. HF and LF were log-transformed for statistical analysis. Linear mixed-effect models were used to analyze the association between sleep patterns and CAM.
  
  
  RESULTS
  After adjusting for major confounders, increased sleep duration variability and efficiency variability were significantly associated with lower HRV and higher HR during the 39-h, as well as separated by daytime and nighttime. For instance, a 1-h increase in sleep duration variability is associated with -0.14(0.04), -0.12(0.06), and -0.16(0.05) ms(2) decrease in total, daytime, and nighttime HF, respectively. No associations were found between sleep duration, or sleep efficiency and HRV.
  
  
  CONCLUSIONS
  Higher habitual sleep duration variability and efficiency variability are associated with lower HRV and higher HR, suggesting that an irregular sleep pattern has an adverse impact on CAM, even in healthy adolescents.
authors.affiliation: Department of Public Health Sciences, Penn State University College of Medicine, Hershey, PA 17033, USA.
authors.forename: Sol M
authors.initials: SM
authors.lastname: Rodríguez-Colón
authors.affiliation: Department of Public Health Sciences, Penn State University College of Medicine, Hershey, PA 17033, USA.
authors.forename: Fan
authors.initials: F
authors.lastname: He
authors.affiliation: Sleep Research &Treatment Center, Department of Psychiatry, Penn State University College of Medicine, Hershey, PA 17033, USA.
authors.forename: Edward O
authors.initials: EO
authors.lastname: Bixler
authors.affiliation: Sleep Research &Treatment Center, Department of Psychiatry, Penn State University College of Medicine, Hershey, PA 17033, USA.
authors.forename: Julio
authors.initials: J
authors.lastname: Fernandez-Mendoza
authors.affiliation: Sleep Research &Treatment Center, Department of Psychiatry, Penn State University College of Medicine, Hershey, PA 17033, USA.
authors.forename: Alexandros N
authors.initials: AN
authors.lastname: Vgontzas
authors.affiliation: Sleep Research &Treatment Center, Department of Psychiatry, Penn State University College of Medicine, Hershey, PA 17033, USA.
authors.forename: Susan
authors.initials: S
authors.lastname: Calhoun
authors.affiliation: School of Public Health, Shanghai Jiao Tong University, Shanghai, China.
authors.forename: Zhi-Jie
authors.initials: ZJ
authors.lastname: Zheng
authors.affiliation: Department of Public Health Sciences, Penn State University College of Medicine, Hershey, PA 17033, USA. Electronic address: dliao@psu.edu.
authors.forename: Duanping
authors.initials: D
authors.lastname: Liao
mesh_terms: D056044:Actigraphy; D000293:Adolescent; D001341:Autonomic Nervous System / Q000503:physiopathology*; D002648:Child; D002940:Circadian Rhythm / Q000502:physiology; D015331:Cohort Studies; D015716:Electrocardiography, Ambulatory; D005260:Female; D006184:Habits; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008297:Male; D010414:Pennsylvania; D012890:Sleep / Q000502:physiology*; D012891:Sleep Apnea Syndromes / Q000453:epidemiology* / Q000503:physiopathology*
keywords: Adolescent; Cardiac autonomic modulation; Habitual sleep variability; Heart rate variability; Sleep duration; Sleep efficiency