title: Episodes of severe hypoglycemia in type 1 diabetes are preceded and followed within 48 hours by measurable disturbances in blood glucose.
abstract: This study quantifies blood glucose (BG) disturbances occurring before and after episodes of severe hypoglycemia (SH). For 6-8 months, 85 individuals with type 1 diabetes and a history of SH (age, 44+/-10 yr; 41 women and 44 men; duration of diabetes, 26+/-11 yr; hemoglobin A1c, 7.7+/-1.1%) used Lifescan One Touch BG meters for self-monitoring three to five times daily and recorded the date and time of SH episodes in diaries. For each subject, the timing of SH episodes was located in the temporal stream of SMBG readings recorded by the meter, and characteristics, including the Low BG index (LBGI), were computed in 24-h increments. In the 24-h period before the SH episode LBGI rose (P < 0.001), average BG was lower (P = 0.001), and BG variance increased (P = 0.001). In the 24 h after SH, LBGI and BGvariance remained elevated (P < 0.001), but average BG returned to baseline. These disturbances disappeared in 48 h. On the basis of LBGI we identified subjects at low, moderate, and high risk of SH, who reported, on the average, 1.7, 3.4, and 7.4 SH episodes (P < 0.005) during the study. In addition, we designed an algorithm that predicted 50% of all SH episodes that occurred in this subject group. We conclude that episodes of SH are preceded and followed by quantifiable BG disturbances, which could be used to devise warnings of imminent SH.
authors.affiliation: University of Virginia Health System and National Science Foundation Center for Biological Timing, Charlottesville 22908, USA.
authors.forename: B P
authors.initials: BP
authors.lastname: Kovatchev
authors.forename: D J
authors.initials: DJ
authors.lastname: Cox
authors.forename: L S
authors.initials: LS
authors.lastname: Farhy
authors.forename: M
authors.initials: M
authors.lastname: Straume
authors.forename: L
authors.initials: L
authors.lastname: Gonder-Frederick
authors.forename: W L
authors.initials: WL
authors.lastname: Clarke
mesh_terms: D000204:Activity Cycles; D000328:Adult; D001786:Blood Glucose / Q000378:metabolism*; D015190:Blood Glucose Self-Monitoring; D003922:Diabetes Mellitus, Type 1 / Q000097:blood* / Q000188:drug therapy / Q000503:physiopathology*; D005260:Female; D006442:Glycated Hemoglobin / Q000032:analysis; D006801:Humans; D007003:Hypoglycemia / Q000097:blood / Q000503:physiopathology*; D007328:Insulin / Q000627:therapeutic use; D008297:Male; D010507:Periodicity; D012008:Recurrence
chemical_list: D001786:Blood Glucose; D006442:Glycated Hemoglobin; D007328:Insulin