Blood Sugar, Disease, and Nondisease

Although nobody has ever actually seen one [1], an elevated blood sugar is a very real thing to the patient with diabetes, to the physician or other medical person helping that patient deal with the disease, and to the epidemiologist trying to unravel the intricate mysteries of disordered blood sugars in populations. The Expert Committee on the Diagnosis and Classification of Diabetes Mellitus has now published a report, the result of 2 years of intensive labor, that lays out new criteria for assigning meaning to blood sugars [2]. Why did the group undertake this work? Why now? And why should we care?

The last time an expert group in the United States put forth guidelines for diagnosing diabetes in individual patients and classifying populations as normal and abnormal with respect to blood sugar levels was 1979-nearly 20 years ago. In that year, the National Diabetes Data Group formally recognized two principal abnormal metabolic states: insulin-dependent diabetes mellitus, or type 1 diabetes, and non–insulin-dependent diabetes mellitus, or type 2 diabetes, while also recognizing gestational diabetes, malnutrition-related diabetes, and other types. The group provided specific diagnostic and classification schemes based on the best information then available, using the predictive-that is, diagnostic-power of blood sugar levels. This scheme was adopted in 1980 by the World Health Organization (WHO) Expert Committee on Diabetes and later by the WHO Study Group on Diabetes Mellitus.

As suggested by others [3, 4], the most obvious reason for developing new criteria was to take advantage of the new and better information about the predictive power of blood sugar levels that has become available during the past 20 years. Although the blood sugar level itself has long been appreciated as a predictor of disease risk, blood sugar levels fluctuate substantially, from hour to hour and day …