title: Impact of glycemic control on heart rate variability in youth with type 1 diabetes: the SEARCH CVD study.
abstract: OBJECTIVE
  This study explored the role of glycemic control on cardiac autonomic function, measured by heart rate variability (HRV), in youth with type 1 diabetes.
  
  
  METHODS
  A retrospective cohort of 345 youth with type 1 diabetes (mean age, 18.5 years; duration, 10 years) participating in the SEARCH for Diabetes in Youth study were enrolled in the ancillary SEARCH Cardiovascular Disease (CVD) study. Anthropometric, metabolic, and HRV parameters were collected at the current research visit. Glycemic control over time was assessed by the mean glycated hemoglobin (A1c) levels collected over the past 6 years. Multiple linear regression analysis assessed the association between A1c over time and HRV parameters, independent of demographic and CVD risk factors. Participants were categorized into four glycemic control categories based on their mean A1c over time: Group 1, optimal (mean A1c, ≤7.4%); Group 2 (mean A1c, 7.5-8.4%); Group 3 (mean A1c, 8.5-9.4%), and Group 4, poor (mean A1c, ≥9.5%), and a linear trend was explored across these categories.
  
  
  RESULTS
  For every 1% increase in the average A1c over 6 years there was a 5% decrease in the SD of the normal RR interval (SDNN) (P=0.02) and 7% decrease in the root mean square successive difference of the RR interval (RMSSD) (P=0.02), independent of demographic and traditional CVD risk factors. A dose-response relationship between worsening glucose control categories and measures of overall reduced HRV was found.
  
  
  CONCLUSIONS
  Chronic hyperglycemia is the main determinant of early cardiac autonomic dysfunction, manifested as reduced overall HRV and parasympathetic loss, among youth with type 1 diabetes.
authors.affiliation: 1 Department of Epidemiology, Colorado School of Public Health , Aurora, Colorado.
authors.forename: Mamta
authors.initials: M
authors.lastname: Jaiswal
authors.forename: Tasha E
authors.initials: TE
authors.lastname: Fingerlin
authors.forename: Elaine M
authors.initials: EM
authors.lastname: Urbina
authors.forename: R Paul
authors.initials: RP
authors.lastname: Wadwa
authors.forename: Jennifer W
authors.initials: JW
authors.lastname: Talton
authors.forename: Ralph B
authors.initials: RB
authors.lastname: D'Agostino
authors.forename: Richard F
authors.initials: RF
authors.lastname: Hamman
authors.forename: Stephen R
authors.initials: SR
authors.lastname: Daniels
authors.forename: Santica M
authors.initials: SM
authors.lastname: Marcovina
authors.forename: Larry M
authors.initials: LM
authors.lastname: Dolan
authors.forename: Dana
authors.initials: D
authors.lastname: Dabelea
mesh_terms: D000293:Adolescent; D001341:Autonomic Nervous System / Q000503:physiopathology*; D001786:Blood Glucose / Q000378:metabolism*; D002318:Cardiovascular Diseases / Q000097:blood / Q000453:epidemiology / Q000517:prevention & control*; D008078:Cholesterol, LDL / Q000097:blood; D003120:Colorado / Q000453:epidemiology; D003922:Diabetes Mellitus, Type 1 / Q000097:blood / Q000453:epidemiology / Q000503:physiopathology*; D003925:Diabetic Angiopathies / Q000097:blood / Q000453:epidemiology / Q000517:prevention & control*; D005260:Female; D006442:Glycated Hemoglobin / Q000378:metabolism; D006339:Heart Rate; D006801:Humans; D006943:Hyperglycemia / Q000097:blood / Q000453:epidemiology / Q000503:physiopathology*; D016014:Linear Models; D008297:Male; D009820:Ohio / Q000453:epidemiology; D012189:Retrospective Studies; D012307:Risk Factors; D014280:Triglycerides / Q000097:blood; D059289:Vascular Stiffness
chemical_list: D001786:Blood Glucose; D008078:Cholesterol, LDL; D006442:Glycated Hemoglobin; D014280:Triglycerides; C517652:hemoglobin A1c protein, human