Dawn Phenomenon Found in 101 of 114 Patients
Dawn Phenomenon - A condition some people with insulin-dependent diabetes experience resulting in a significant rise in their early morning blood glucose values (around 5:00 am), possibly requiring additional insulin to control. The incidence and severity of the dawn phenomenon has been debated since its discovery by Schmidt et al in 1981.
An Italian group has studied 114 subjects with Type I diabetes (none using a pump) on 3 separate occasions to assess their insulin requirements between midnight and morning. The results revealed 89% of the patients had an increased need for insulin during the dawn hours. This increase was only 20%, which was lower than previously reported.
The results were extremely reproducible on different days in the same patient. A more pronounced dawn phenomenon tended to occur in patients who were in poorer control, had a shorter duration of diabetes, had adequate counter-regulatory hormones, and used large amounts of insulin.
Dawn Phenomenon is associated with:
- Poor Control
- Short duration of diabetes
- Adequate counter-regulatory hormones
- High insulin needs
Perriello concludes his article with: "The dawn phenomenon is a very frequent event in subjects with Type I diabetes mellitus; its magnitude is lower than initially indicated; it is highly reproducible from day to day; it is influenced by factors such as, duration of diabetes, quality of antecedent glycemic control, state of counter-regulation system to hypoglycemia, and insulin sensitivity."
Perriello G et al: 1991:42:21-8
Editor's Note:
Since the dawn phenomenon is a common occurrence and is reproducible from day to day, patients who use the continuous subcutaneous infusion pump can easily increase the basal rate prior to the dawn hours and effect smooth control until the fasting time. This technique is a consistently effective way to manage the dawn phenomenon.
Treating fasting hyperglycemia requires an assessment of the reason for the elevation of blood glucose. Before treating fasting hyperglycemia, it is necessary to access the reason for the elevation. It may be due to too little insulin, too much insulin with nocturnal hypoglycemia, or the dawn phenomena. For many years the assumption was that insufficient insulin provision accounted for a higher than normal fasting blood sugar, and physicians would give increased amounts of insulin with the expectation that morning glucose levels would improve. Frequently nocturnal hypoglycemia would occur and even higher fasting plasma glucose levels would result. Liability of control still exists as a result of physician prescribed insulin doses that are greater than required.
The recognition that a rise in blood glucose may occur transiently between 4 AM and 8 AM in persons with both Type I and Type II diabetes offers another explanation for elevation in fasting plasma glucose. This dawn phenomenon with increased insulin requirements during those hours poses an additional consideration in determining a treatment plan to correct fasting hyperglycemia.
Self monitoring of blood sugar levels during the nighttime will confirm the existence of a rising blood sugar during the dawn hours requiring an adjustment in timing of insulin provision. Recognizing the reason for fasting hyperglycemia is critical in taking appropriate steps to correct the problem.
Sherman M. Holvey, Ph.D.
