title: Influence of caffeine on heart rate variability in patients with long-standing type 1 diabetes.
abstract: OBJECTIVE
  The effect of caffeine on cardiovascular health remains controversial. Patients with long-standing type 1 diabetes are at risk of autonomic failure and sudden cardiac death. We investigated the effects of caffeine on autonomic dysfunction (as assessed by heart rate variability [HRV]) in this high-risk group and in a control population.
  
  
  METHODS
  Using a randomized blinded, placebo-controlled, crossover design trial, we examined 2 weeks of caffeine consumption (250 mg twice daily) on HRV in 20 type 1 diabetic patients and 10 matched healthy volunteers.
  
  
  RESULTS
  Baseline HRV was blunted in the diabetic patients (P < 0.0005 vs. control subjects) and markedly increased by caffeine in both groups (+103% in the group with diabetes [P = 0.009] and +38% in control subjects [P = 0.002]). The caffeine-associated increase in HRV was not statistically different between the control and the type 1 diabetes groups (P = 0.16).
  
  
  CONCLUSIONS
  Modest amounts of caffeine improved autonomic function in diabetic patients and healthy volunteers. For individuals with abnormal HRV, regular caffeine use may have the potential to reduce the risk of cardiovascular events.
authors.affiliation: Bournemouth Diabetes & Endocrine Centre, Royal Bournemouth Hospital, Bournemouth, UK. tristan.richardson@rbch-tr.swest.nhs.uk
authors.forename: Tristan
authors.initials: T
authors.lastname: Richardson
authors.forename: Adrian
authors.initials: A
authors.lastname: Rozkovec
authors.forename: Peter
authors.initials: P
authors.lastname: Thomas
authors.forename: Jacqueline
authors.initials: J
authors.lastname: Ryder
authors.forename: Candy
authors.initials: C
authors.lastname: Meckes
authors.forename: David
authors.initials: D
authors.lastname: Kerr
mesh_terms: D000328:Adult; D001794:Blood Pressure / Q000187:drug effects / Q000502:physiology; D002110:Caffeine / Q000494:pharmacology*; D003069:Coffee; D018592:Cross-Over Studies; D003922:Diabetes Mellitus, Type 1 / Q000503:physiopathology*; D005260:Female; D006442:Glycated Hemoglobin / Q000032:analysis; D006339:Heart Rate / Q000187:drug effects* / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D012016:Reference Values
chemical_list: D002110:Caffeine; D003069:Coffee; D006442:Glycated Hemoglobin