Diabetes Care, Vol 18, Issue 4 517-522, Copyright © 1995 by American Diabetes Association

ARTICLES

Reduced awareness of hypoglycemia in adults with IDDM. A prospective study of hypoglycemic frequency and associated symptoms

WL Clarke, DJ Cox, LA Gonder-Frederick, D Julian, D Schlundt and W Polonsky
Department of Pediatrics, University of Virginia Health Sciences Center, Charlottesville 22908, USA.

OBJECTIVE--To prospectively evaluate the frequency and severity of hypoglycemic episodes in IDDM subjects who declare themselves to have reduced awareness of hypoglycemia, to validate their self-designations in their natural environment, and to determine objectively the presence or absence of autonomic and neuroglycopenic symptoms associated with their low blood glucose (BG) levels. RESEARCH DESIGN AND METHODS--A total of 78 insulin-dependent diabetes mellitus (IDDM) subjects (mean age 38.3 +/- 9.2 years; duration of diabetes 19.3 +/- 10.4 years) completed two sets of assessments separated by 6 months. The assessments included reports of frequency and severity of low BG, symptoms associated with low BG, and a BG symptom/estimation trial using a hand-held computer (HHC). Diaries of hypoglycemic episodes were kept for the intervening 6 months. HbA1 levels were determined at each assessment. RESULTS--Of the subjects, 39 declared themselves as having reduced awareness of hypoglycemia (reduced-awareness subjects). There were no differences between these reduced-awareness subjects and aware subjects with regard to age, sex, disease duration, insulin dose, or HbA1. During the HHC trials, reduced-awareness subjects were significantly less accurate in detecting BG < 3.9 mmol/l (33.2 +/- 47 vs. 47.6 +/- 50% detection, P = 0.001) and had significantly fewer autonomic (0.41 +/- 0.82 vs. 1.08 +/- 1.22, P = 0.006, reduced-awareness vs. aware) and neuroglycopenic (0.44 +/- 0.85 vs. 1.18 +/- 1.32, P = 0.004, reduced-awareness vs. aware) symptoms per subject. Prospective diary records revealed that reduced-awareness subjects experienced more moderate (351 vs. 238, P = 0.026) and severe (50 vs. 17, P = 0.0062) hypoglycemic events. The second assessment results were similar to the first and verified the reliability of the data. CONCLUSIONS--IDDM subjects who believe they have reduced awareness of hypoglycemia are generally correct. They have a history of more moderate and severe hypoglycemia, are less accurate at detecting BG < 3.9 mmol/l, and prospectively experience more moderate and severe hypoglycemia than do aware subjects. Neither disease duration nor level of glucose control explains their reduced awareness of hypoglycemia. Reduced-awareness individuals may benefit from interventions designed to teach them to recognize all of their potential early warning symptoms.
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