Biology Reference
In-Depth Information
contributes to higher rates of morbidity—people with diabetes are at
higher risk for retinal disease, which is the leading cause of adult
blindness; renal disease, which represents half of all kidney failures; and
neuropathy, which leads to more than 65,000 amputations annually.
Cardiovascular disease is also two to four times more common in
diabetics, and is also more morbid, more lethal, and benefits less from
modern interventions, such as bypass surgery or stents.
In this chapter, we present a model, developed by some of the authors of
this text, that represents a significant advance in predicting episodes of
hypoglycemia or low BG—one of the most hazardous conditions
resulting from the use of the hormone insulin to treat diabetes. Although
the levels of mathematics and statistics used are elementary, the model,
nonetheless, provides a solution to a problem previously pronounced
virtually unsolvable.
Again, we begin by gathering data, then building a model based on the
data, and finally testing the model with additional data. We shall use
data collected by self-monitoring BG (SMBG) devices from people with
diabetes. The major steps of model-building process are:
1. Rescale the data to obtain symmetric samples and thus ensure that
certain well-known statistical techniques will be valid.
2. Define a ''risk function'' that measures the risk of dangerously low
and high deviations of BG from clinically safe levels.
3. Test the risk function to determine whether it is indeed a superior
tool for predicting future episodes of severe hypoglycemia.
I. HISTORICAL OVERVIEW
Aretaeus's grim description of diabetes given in the beginning of this
chapter summarizes all that was known about this disease for nearly
1700 years, until physicians working in the late nineteenth century began
to recognize the connection between the pancreas and diabetes. This
connection was later narrowed to specific parts of the pancreas: the islets
of Langerhans. The islets of Langerhans contain the beta cells that
produce insulin—a hormone discovered in 1921 by the Canadian
surgeon Frederick Banting (1891-1941) and his assistant, Charles Herbert
Best (1899-1978).
The discovery of the action of insulin was one of the greatest
achievements in medicine: diabetes, once an automatic death sentence,
was no longer a fatal disease. The chronicles of medicine trace this
discovery to Banting's 1920 visit to the University of Toronto, when he
spoke to John J. R. Macleod (1876 -1935), who was the head of the
department of physiology and an expert in glucose metabolism and
diabetes. Banting presented to Macleod an idea on how to find the cause
