Type 1 Diabetics May Sleep Through Nocturnal Hypoglycemia

Research shows that patients with type 1 diabetes often sleep through overnight episodes of hypoglycemia, increasing the risk that they will experience prolonged hypoglycemia. On one night, the research team induced hypoglycemia – a 40mg/dL (2.2 mmol/L) decrease in plasma glucose — by infusing insulin over 60 minutes starting as soon as polysomnography indicated that stage 2 sleep had been reached in 16 type 1 diabetic patients and 16 healthy controls matched for gender, age, and BMI. On a separate control night, normal blood sugar levels were maintained.

According to a report of the study in PLoS Medicine, only one of the 16 diabetic patients, as compared to 10 nondiabetic patients, awakened upon hypoglycemia (p = 0.001). None of the study subjects in either group awakened on the control night.

This study shows that the awakening response to hypoglycemia is impaired in patients with type 1 diabetes, note Dr. Bernd Schultes and colleagues from the University of Lubeck, Germany in their report.

"The lack of an awakening response," they discovered, "was paralleled by an absence of clear-cut counterregulatory hormonal responses to hypoglycemia in the great majority of type 1 diabetic patients."

That is, in all of the subjects from both groups who woke to hypoglycemia and in five who did not awaken (3 diabetics and 2 nondiabetic controls), plasma epinephrine levels increased with hypoglycemia by at least 100%.

"A temporal pattern was revealed such that increases in epinephrine in all participants who awakened started always before polysomnographic signs of wakefulness," the authors note.

In a commentary, Drs. Ilan Gabriely and Harry Shamoon from Albert Einstein College of Medicine, Bronx, New York, write that this study "strongly supports and further advances the current notion of type 1 diabetes mellitus susceptibility to nocturnal hypoglycemia and shows a clear relationship between awakening and activation of the counterregulatory response to hypoglycemia, although a cause-effect could not be established with this study design."

Dr. Shultes and colleagues write that given "the potentially harmful effects of nocturnal hypoglycemia, which can even be fatal, restoring a proper awakening response to hypoglycemia is a therapeutic goal of utmost importance to these patients."
PLoS Medicine 2007;4:e69.

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