The phenomena of hypoglycemic unawareness was studied in forty three people with type I diabetes in an attempt to find a common bond between people who lack hypoglycemic warning signs.
This trial, conducted mainly at the University of Pittsburgh School of Medicine, differed from other studies done on the subject in that the researchers actually induced hypoglycemia in the subjects, and in the non-diabetic control group, to see what happens in the bodies of people who do, and people who do not, recognize when blood glucose levels are getting dangerously low. Research for the study was also conducted in Greece and several other cities in the United States.
The researchers hooked the subjects up to an intravenous drip providing insulin and glucose, and a machine to test blood glucose. They then brought glucose levels down to a concentration of 77 mg/dl over a period of 45 minutes, during which the subjects underwent a series of tests to determine if hypoglycemic warning signs were setting in. The 77 mg/dl level was maintained for 45 minutes before the process was repeated with step-wise drops in blood glucose levels to 65, 54, and 41 respectively. At each level, the subjects were re-tested for warning signs of hypoglycemia.
Of the 43 people with type I diabetes, 11 people, or 26% of the group, were classified as having hypoglycemic unawareness.
Compared with the other patients, the unaware group had lower HbA1c levels and a longer duration of diabetes. The study also suggested that the unaware group also had increased insulin sensitivity during the episode.
The group of subjects who were found to be unaware reported 36 severe hypoglycemic episodes requiring another person’s assistance to recover in the three months before the study. Of the group who showed no unawareness, only 3 needed outside assistance during a hypoglycemic episode in the previous three months.
No real difference was found in the deterioration of functioning between the groups, but the unaware group did not begin to experience most symptoms until the glucose concentrations were almost 20 points lower. Mental symptoms started to affect the unaware group when their glucose levels were about 5 points lower than the others.
The researchers concluded that the highest occurrence of hypoglycemia unawareness takes place in patients with a longer duration of diabetes and tighter glycemic control. They found that unawareness can occur without the presence of neuropathy, as was previously suspected, according to the results of the study which were published in Diabetes Care (Dec. 1994).