title: Effect of Fasting Blood Glucose Level on Heart Rate Variability of Healthy Young Adults.
abstract: BACKGROUND
  Previous studies reported increased risk of cardiac events in subjects with fasting blood glucose (FBG) levels lower than the diagnostic threshold of diabetes mellitus. However, whether increased cardiac events in those with upper normal FBG is secondary to the shift of their cardiac sympathovagal balance towards sympathetic predominance is unknown.
  
  
  OBJECTIVE
  To assess the association between FBG levels and cardiac autonomic modulation (CAM) in euglycaemic healthy subjects based on heart rate variability (HRV) derived indices.
  
  
  METHODS
  The study enrolled 42 healthy young adults. Following sociodemographic and clinical assessment, blood samples were collected to measure FBG levels. Five minutes ECG recordings were performed to all participants to obtain frequency domain HRV measurements, namely the natural logarithm (Ln) of total power (LnTP), very low frequency (LnVLF), low frequency (LnLF) and high frequency (LnHF), low frequency/ high frequency ratio (LnLF/HF), normalized low frequency (LF Norm) and high frequency (HF Norm).
  
  
  RESULTS
  FBG levels correlated positively with LnHF (r = 0.33, P = 0.031) and HF Norm (r = 0.35, P = 0.025) and negatively with LF Norm (r = -0.35, P = 0.025) and LnLF/HF (r = -0.33, P = 0.035). LnHF and HF Norm were significantly decreased in subjects with the lower (4.00 (1.34) ms2/Hz and 33.12 (11.94) n.u) compared to those with the upper FBG quartile (5.64 (1.63) ms2/Hz and 49.43 (17.73) n.u, P = 0.013 and 0.032 respectively). LF Norm and LnLF/HF were significantly increased in subjects with the lower (66.88 (11.94) n.u and 0.73 (0.53)) compared to those with the higher FBG quartile (50.58 (17.83) n.u and 0.03 (0.79), P = 0.032 and 0.038 respectively).
  
  
  CONCLUSIONS
  The present study is the first to demonstrate that rise of blood glucose concentration, within physiological range, is associated with higher parasympathetic, but lower sympathetic CAM. Further researches are needed to set out the glycemic threshold beyond which further increase in glucose level readjusts sympathovagal balance towards sympathetic predominance again.
authors.affiliation: Department of Physiology, Faculty of Medicine and Health Sciences, Al-Neelain University, Khartoum, Sudan.
authors.forename: Mohamed Faisal
authors.initials: MF
authors.lastname: Lutfi
authors.affiliation: Department of Physiology, Faculty of Medicine and Health Sciences, Al-Neelain University, Khartoum, Sudan.
authors.forename: Ramaze Farouke
authors.initials: RF
authors.lastname: Elhakeem
mesh_terms: D000328:Adult; D015415:Biomarkers; D001786:Blood Glucose; D005215:Fasting; D005260:Female; D006339:Heart Rate; D006801:Humans; D008297:Male; D062486:Public Health Surveillance; D055815:Young Adult
chemical_list: D015415:Biomarkers; D001786:Blood Glucose