Diabetes - Description
Diabetes in African Americans?Today, diabetes mellitus is one of the most serious health challenges facing the more than 30 million African Americans. The following statistics illustrate the magnitude of this disease among African Americans.
How Many African Americans Have Diabetes?National Health Interview Surveys (NHIS) conducted between 1963 and 1990 show that African Americans have a rising prevalence of diabetes. (Prevalence is the percentage of cases in a population.) Most African Americans with diabetes have Type 2, or noninsulin-dependent diabetes. Type 2 diabetes usually develops after age 40. However, in high-risk populations, susceptible people may develop it at a younger age. A small number of African Americans have Type I or insulin-dependent diabetes, which usually develops before age 20.
NHIS conducted from 1991 to 1992 indicate higher rates of diabetes among African Americans than among white Americans. At age 45 or older, the prevalence of diabetes is 1.4 to 2.3 times as frequent in blacks as in whites. The greatest difference seen in NHIS was among people aged 65 to 74. Figure 1 details these 1991-92 NHIS statistics. Statistics collected in 1993 indicate that in this age group, 17.4 percent of black Americans had diagnosed diabetes, compared to 9.5 percent of white Americans.
Juvenile Onset Type 1 Diabetes Mellitus?
What is it?Type 1 diabetes is a complex disorder caused by the body's inability to produce insulin. Insulin is a hormone manufactured and secreted by the pancreas. Specifically, it is produced by cells called beta cells, which are located in a region of the pancreas called the islets of Langerhans. Insulin is essential for the cells of your body to metabolize glucose properly and function normally.
Type 1 diabetes accounts for only 5 percent to 10 percent of all cases of diabetes. The other forms are type 2 diabes and gestational diabetes. Type 1 diabetes has also been known as insulin-dependent mellitus (IDDM), juvenile onset diabetes mellitus, ketosis-prone diabetes mellitus and immune-mediated diabetes. It usually begins in childhood or adolescence, but is a lifelong disease, since there is no cure. However, effective treatment allows most people with type 1 diabetes to live long lives.
Type 1 diabetes is an autoimmune disease that affects 0.3% of the world's population. It is caused by autoaggressive T cells that infiltrate the pancreas and eventually destroy the insulin-producing B-islet cells. This results in an increase in glucose levels, which are normally kept in check by insulin. Autoimmune diabetes usually affects young people, who are then dependent on an artificial source of insulin for life. The identity of the self proteins in the pancreatic islets that target the cells for autoimmune destruction has long been debated. Yoon, et al, report a real breakthrough in understanding the etiology of type 1 diabetes. They showed that a single self protein expressed by B-islet cells, glutamic acid, decarboxylase (GAD), controls the development of diabetes in the nonobese mouse diabetic (NOD) mouse (a good animal model of human type 1 diabetes.
Type 1 diabetes has a prevalence rate of approximately 8% in African-Americans.
Type 2 Diabetes
What Risk Factors Increase the Chance of Developing Type 2 Diabetes?The frequency of diabetes in black adults is influenced by the same risk factors that are associated with Type 2 diabetes in other populations. Three categories of risk factors increase the chance of developing Type 2 diabetes in African Americans. The first is genetics, which includes inherited traits and group ancestry. The second is medical risk factors, including impaired glucose tolerance, hyperinsulinemia and insulin resistance, and obesity. The third is lifestyle risk factors, including physical activity.
Genetic Risk FactorsInherited Traits
Researchers suggest that African Americans and recent African immigrants to America have inherited a "thrifty gene" from their African ancestors. Years ago, this gene enabled Africans, during "feast and famine" cycles, to use food energy more efficiently when food was scarce. Today, with fewer "feast and famine" cycles, the thrifty gene that developed for survival may instead make weight control more difficult. This genetic predisposition, along with impaired glucose tolerance (IGT), often occurs together with the genetic tendency toward high blood pressure.
Medical Risk FactorsImpaired Glucose Tolerance (IGT)
People with IGT have higher-than-normal blood glucose levels but not high enough to be diagnosed as diabetes. Some argue that IGT is actually an early stage of diabetes. African-American men and women differ in their development of IGT. As black men grow older, they develop IGT at about the same rates as white American men and women. African-American women, who have higher rates of diabetes risk factors, convert more rapidly from IGT to overt diabetes than black men and white women and men.
Hyperinsulinemia and Inssulin Resistance
Some recent evidence shows that the degree to which obesity is a risk factor for diabetes may depend on the location of the excess weight. Truncal, or upper body obesity, is a greater risk factor for Type 2 diabetes, compared to excess weight carried below the waist. One study showed that African Americans have a greater tendency to develop upper-body obesity, which increases their risk of Type 2.
Although African Americans have higher rates of obesity, researchers do not believe that obesity alone accounts for their higher prevalence of diabetes. Even when compared to white Americans with the same levels of obesity, age, and socioeconomic status, African Americans still have higher rates of diabetes. Other factors, yet to be understood, appear to be at work.
Lifestyle Risk FactorsPhysical Activity
Physical activity is a strong protective factor against Type 2 diabetes. Researchers suspect that a lack of exercise is one factor contributing to the unusually high rates of diabetes in older African-American women.
How Does Diabetes Affect African-American Young People?African-American children have lower rates of Type 1 diabetes than white American children. The prevalence of Type 1 diabetes in white American children aged 15 and younger is nearly twice as high as in African-American children of the same age.
Researchers tend to agree that genetics probably makes Type 1 diabetes more common among children with European ancestry. In fact, African-American children with some European ancestry have slightly higher prevalence of Type I diabetes. T'his incidence is also influenced by environmental and lifestyle factors.
How Does Diabetes Affect African-American Women During Pregnancy?Gestational diabetes, which develops in about 2 to 5 percent of all pregnant women, usually resolves after childbirth. Several studies have shown that African-American women have a higher rate of gestational diabetes. An Illinois study showed an 80 percent higher incidence of gestational diabetes in African Americans compared with white women. Once a woman has had gestational diabetes, she has an increased risk of developing gestational diabetes in future pregnancies. In addition, experts estimate that about half of women with gestational diabetes regardless of race develop Type 2 diabetes within 20 years of the pregnancy.
How Do Diabetes Complications Affect African Americans?Compared to white Americans, African Americans experience higher rates of three diabetes complications - blindness, kidney failure, and amputations. They also experience greater disability from these complications. Some factors that influence the frequency of these complications, such as delay in diagnosis and treatment of diabetes, denial of diabetes, abnormal blood lipids, high blood pressure, and cigarette smoking, can be influenced by proper diabetes management.
Kidney FailureAfrican Americans experience kidney failure, also called end-stage renal disease (ESRD), from 2.5 to 5.5 times more often than white Americans. Interestingly though, hypertension, not diabetes, is the leading cause of kidney failure in black Americans. Hypertension accounts for almost 38 percent of ESRD cases in African Americans, whereas diabetes causes 32.5 percent. In spite of their high rates of the disease, African Americans have better survival rates from kidney failure than white Americans.
Visual ImpairmentThe frequency of severe visual impairment is 40 percent higher in African Americans with diabetes than in white Americans. Blindness caused by diabetic retinopathy is twice as common in blacks as in whites. Compared to white women, black women are three times more likely to become blind from diabetes. African-American men have a 30 percent higher rate of blindness from diabetes than white American men. Diabetic retinopathy may occur more frequently in black Americans than whites because of their higher rate of hypertension.
AmputationsAfrican Americans undergo more diabetes-related lower-extremity amputations than white or Hispanic Americans. One study of 1990 U.S. hospital discharge figures showed amputation rates for African Americans with diabetes were 19 percent higher than for white Americans. In a 1991 California study, however, African Americans were 72 percent more likely to have diabetes-related amputations than white Americans, and 117 percent more likely than Hispanic Americans.
Does Diabetes Cause Excess Deaths in African Americans?Diabetes was an uncommon cause of death among African Americans at the turn of the century. By 1993, however, according to the Centers for Disease Control and Prevention's National Center for Health Statistics, death certificates listed diabetes as the fifth leading cause of death for African Americans aged 45 to 64, and the third leading cause of death for those aged 65 and older in 1990. Diabetes is more dangerous for African-American women, for whom it was the third leading cause of death for all ages in 1990.
Diabetes death rates may actually be higher than these studies show for two reasons. First, diabetes might not have been diagnosed. Second, many doctors do not list diabetes as a cause of death, even when the person was known to have diabetes.
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