title: Eighteen years of fair glycemic control preserves cardiac autonomic function in type 1 diabetes.
abstract: OBJECTIVE
  To study the association between 18 years of mean HbA(1c) and cardiac autonomic function in type 1 diabetic patients having used intensive insulin treatment.
  
  
  METHODS
  A total of 39 patients with type 1 diabetes were followed during 18 years, and HbA(1c) was measured yearly. At 18 years follow-up heart rate variability (HRV) measurements were used to assess cardiac autonomic function. Standard cardiac autonomic tests during normal breathing, deep breathing, the Valsalva maneuver, and the tilt test were performed. Maximal heart rate increase during exercise electrocardiogram and minimal heart rate during sleep were also used to describe cardiac autonomic function.
  
  
  RESULTS
  We present the results for patients with mean HbA(1c) <8.4% (two lowest HbA(1c) tertiles) compared with those with HbA(1c) > or = 8.4% (highest HbA(1c) tertile). All of the cardiac autonomic tests were significantly different in the high- and the low-HbA(1c) groups, and the most favorable scores for all tests were seen in the low-HbA(1c) group. In the low-HbA(1c) group, the HRV was 40% during deep breathing, and in the high-HbA(1c) group, the HRV was 19.9% (P = 0.005). Minimal heart rate at night was significantly lower in the low-HbA(1c) groups than in the high-HbA(1c) group (P = 0.039). With maximal exercise, the increase in heart rate was significantly higher in the low-HbA(1c) group compared with the high-HbA(1c) group (P = 0.001).
  
  
  CONCLUSIONS
  Mean HbA(1c) during 18 years was associated with cardiac autonomic function. Cardiac autonomic function was preserved with HbA(1c) <8.4%, whereas cardiac autonomic dysfunction was impaired in the group with HbA(1c) > or = 8.4%.
authors.affiliation: Diabetes Research Center, Aker and Ulleval University Hospitals, and Department of Pediatrics, Ulleval University Hospital, Oslo, Norway. j.r.larsen@ioks.uio.no
authors.forename: Jakob R
authors.initials: JR
authors.lastname: Larsen
authors.forename: Hans
authors.initials: H
authors.lastname: Sjøholm
authors.forename: Tore J
authors.initials: TJ
authors.lastname: Berg
authors.forename: Leiv
authors.initials: L
authors.lastname: Sandvik
authors.forename: Magne
authors.initials: M
authors.lastname: Brekke
authors.forename: Kristian F
authors.initials: KF
authors.lastname: Hanssen
authors.forename: Knut
authors.initials: K
authors.lastname: Dahl-Jørgensen
mesh_terms: D000328:Adult; D001341:Autonomic Nervous System / Q000503:physiopathology*; D003922:Diabetes Mellitus, Type 1 / Q000097:blood / Q000188:drug therapy* / Q000503:physiopathology*; D015444:Exercise; D005260:Female; D006442:Glycated Hemoglobin / Q000378:metabolism*; D006321:Heart / Q000294:innervation*; D006334:Heart Function Tests; D006339:Heart Rate; D006801:Humans; D007004:Hypoglycemic Agents / Q000627:therapeutic use*; D007328:Insulin / Q000627:therapeutic use*; D008297:Male; D008875:Middle Aged; D015656:Respiratory Mechanics; D018667:Tilt-Table Test
chemical_list: D006442:Glycated Hemoglobin; D007004:Hypoglycemic Agents; D007328:Insulin