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The Complex Nature of Diabetes Complications

Mercedes Carnethon
Department of Health Research & Policy
Stanford School of Medicine
December 2001


Persons with adult-onset diabetes are at increased risk for additional health problems, such as heart disease, kidney failure, and blindness. To identify markers or precursors for these health problems, we can use simple physical measurements such as heart rate monitoring, blood, and urine testing. With this information, we can determine how often these complications occur and determine what type of person might develop these complications. My research addresses the following questions: 1) How often do complications from diabetes occur in the population?; and, 2) What personal, environmental, and physical characteristics are associated with the development of (or protection from) diabetes complications? The benefits of this research are multi-fold-we can treat persons at risk for complications before they become sick, and figure out what protects persons against the development of diabetes complications.

Adult-onset diabetes, known as Type 2 diabetes, begins when the body cannot convert the sugars in food to energy. Normally, this sugar, known as glucose, rapidly clears from the blood and is stored as energy. However, in a person with Type 2 diabetes, glucose stays in the blood where it circulates through the body. Glucose reaches all of the body's organs and systems, including the heart, arteries and veins, kidneys, and the neurological systems that control the nerves and eyesight. Sugar in the blood has essentially the same effects as eating too much candy and not brushing your teeth-it causes organ system decay or degeneration. Therefore, the organs of Type 2 diabetics are under a constant sugar attack, which over time causes damage, and places the diabetic at risk of developing secondary diseases, or complications. While all diabetics develop these health problems more frequently than individuals without diabetes, it is not known who among the diabetics will develop complications, nor which complications will arise.

One of the "complex" things about diabetes complications is that we do not know why this glucose attack harms the heart in some persons and the kidneys or neurological system in others. Blood is delivered to the heart via large vessels, so when this organ is harmed by too much glucose it is called "large vessel" disease. In contrast, the kidneys and neurological system receive blood via small vessels, so kidney disease and blindness are referred to as "small vessel" disease complications. Some ethnic groups develop large or small vessel disease more often than others. For example, white diabetics have large vessel disease more often than black diabetics. It is not known whether this is due to genetic, personal (e.g., age, income) or physical differences (e.g., body weight), health behaviors (e.g., diet), or other unknown factors.

We will conduct this study in a large group of diabetic adults representing a cross-section of US society: large numbers of ethnic minorities, males and females, and individuals from a range of social and income classes. Our study will take advantage of recent research that identifies markers or precursors of large (heart) or small (nerve or kidney) vessel diabetes complications. Those measurements include blood draws, urine samples, retinal scans (photographs of the retina in the eye), nerve sensitivity in the feet using light touches, images such as ultrasounds of the arteries (identical to the technique used by doctors to see a growing fetus), and electrocardiographic (ECG) monitoring of heart rate or rhythm. These markers are quick and easy to measure, which makes them ideal to use in a large population study.

We will use a combination of written surveys, interviews, and physical measurements to gather data about possible explanations for these complications. Study participants will complete written surveys about their health habits, such as exercise, diet, sleep patterns, frequency of doctor visits, and use of medications. We will use written and face-to-face interviews to measure symptoms of depression or stress in participants. In a clinical examination, we will measure participants' height, weight, blood pressure, and cholesterol. We will measure whether certain characteristics (personal, environmental, or physical) occur most often with particular types of complications (e.g., poor diet most often associated with large vessel complications).

In addition to measuring how often small and large vessel complications occur among diabetics, results from this study can suggest the causes of some diabetes complications. Further, this research can stress the need for close physician monitoring of patients with particular characteristics. This can lead to advancements in the diagnosis and early treatment of complications, thus improving the health of individuals with Type 2 diabetes.