Epidemiology of Type 2 Diabetes: Focus on Ethnic Minorities

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Prevalence and incidence of diabetes

The rate of diagnosed diabetes has grown steadily over time and is now approaching epidemic proportions. The age-adjusted prevalence rate of diagnosed diabetes increased from 2.77% in 1980 to 4.22% in 1999 [1]. There is also a similar trend in the rates of newly diagnosed cases of diabetes. Between 1980 and 1999 the incidence rate of diabetes increased from 0.23% to 0.34%. Currently, it is estimated that 1.3 million new cases of diabetes are diagnosed each year among people older than 20 years

Prevalence of diabetes complications

Diabetes is a leading cause of cardiovascular disease, stroke, blindness, end-stage renal disease, and nontraumatic lower limb amputations [1]. Matched for age and sex, individuals who have diabetes have twofold to fourfold increased risk of cardiovascular disease–related deaths compared with people who do not have diabetes [1]. Diabetes accounts for 43% of all new cases of end-stage renal disease. Diabetes also accounts for 60% to 70% of cases of neuropathy and 60% of nontraumatic lower limb

Risk factors for development of type 2 diabetes

Several large epidemiologic studies have identified risk factors for the development of type 2 diabetes [4]. These risk factors include belonging to an ethnic minority population, having a first-degree relative who has diabetes, obesity, living a sedentary lifestyle, age greater than 45 years, and having features of the metabolic syndrome (Box 1). The metabolic syndrome is associated with a significantly increased risk of developing diabetes and is characterized by the presence of three or more

Etiology of ethnic disparity

There is some degree of uncertainty about the reasons for racial and ethnic differences in the prevalence and incidence of type 2 diabetes. It is thought that a combination of genetic factors and environmental triggers interact to confer an increased risk of diabetes in ethnic minorities.

Pathophysiology of type 2 diabetes

Type 2 diabetes is characterized by impaired insulin action (insulin resistance) and impaired pancreatic beta cell function. Insulin resistance occurs when there is reduced sensitivity in body tissues to the action of insulin [19]. Over time higher concentrations of insulin are required to stimulate glucose disposal in peripheral tissues and suppress glucose production in the liver [19]. Eventually, functional defects in the pancreatic beta cells prevent adequate insulin production in response

Underlying pathophysiology in ethnic minorities

In ethnic minority groups, the concurrent role of insulin resistance and beta cell dysfunction in predicting the development of type 2 diabetes was confirmed in a longitudinal study of Pima Indians [20]. Studies that compared various populations of West African descendants (including African Americans and native Ghanaians) and whites have reported higher degrees of insulin resistance among West African descendants [21], [22]. These studies have also suggested alterations in hepatic insulin

Mechanisms and mediators of diabetes complications

Theoretically, the increased microvascular complications of diabetes among ethnic minorities may be caused by primary (genetic) susceptibility or secondary (acquired) factors.

Cost of treating diabetes

Several studies have shown that diabetes imposes substantial economic burden on both the individual and society. One of the early studies on the economic burden of diabetes was conducted in 1986 [42]. It showed that the total cost of non–insulin dependent diabetes (type 2 diabetes) was $11.6 billion, of which $6.8 billion was caused by direct medical cost. Another study used data from the 1996 Medical Expenditures Survey to calculate the economic burden of five chronic conditions [43]. The

Cost effectiveness of treatments for diabetes

The UKPDS is the largest study to date on the effectiveness of treatment for type 2 diabetes. The UKPDS was a multicenter, prospective, randomized, intervention trial of approximately 5100 newly diagnosed patients who have type 2 diabetes aimed to determine whether improved blood glucose control prevents complications and reduces associated morbidity and mortality [46]. The planned median follow-up was 9 years (range 3–16 years). Intensive blood-glucose control by either sulfonylureas or

Treatments for type 2 diabetes

Studies have shown that when blood glucose levels are controlled to a similar degree, the rates of diabetic nephropathy, neuropathy, and retinopathy are similar in white and nonwhite patients. In the recently concluded Diabetes Prevention Study, the response rates to intensive lifestyle or pharmacologic intervention were identical in African Americans, Asian Americans and Pacific Islanders, Hispanics, Native Americans, and white Americans [18]. These findings, demonstrating lack of ethnic

Self-monitoring of home blood glucose

SMBG is an important (but underused) tool of diabetes management and education. Performance of SMBG is associated with superior glycemic control [51]. The recommended frequency of SMBG is two to four times daily for insulin-treated patients. The optimal frequency has not been established for patients who have type 2 diabetes treated with oral agents, but regular SMBG (at least once daily) is recommended [49]. The physician should review the results of SMBG and give appropriate feedback.

Diabetes education and counseling

Diabetes

Pharmacologic approaches

The ideal treatment for type 2 diabetes should reverse insulin resistance (and the associated metabolic syndrome); normalize hepatic glucose production; improve beta cell function; and prevent the development of long-term complications [54]. Aggressive glycemic control is needed to maintain hemoglobin A1c levels below 6.5% and to prevent the development of diabetic complications [50]. Medications used for treating diabetes include insulin and oral agents. Pharmacotherapy for diabetes is most

Indications for insulin therapy in type 2 diabetes

In the UKPDS, estimates of pancreatic beta-cell function revealed that in most patients who have type 2 diabetes beta-cell function had decreased by about 50% at the time of diagnosis and continued to deteriorate over time [70]. The progressive decline in beta-cell function predicts a future need for exogenous insulin in type 2 diabetes patients. Immediate insulin therapy is indicated for initial stabilization of type 2 diabetes patients who have ketoacidosis, hyperosmolar state, or severe

Barriers to effective diabetes care

Despite the plethora of effective therapeutic options for the treatment of diabetes, evidence indicates that glycemic control falls short of national guidelines [35]. Suboptimal treatment of diabetes in ethnic minorities can be attributed to barriers at the patient, provider, and health systems levels.

Summary and future directions

To achieve sustained improvements in overall quality of care for diabetes and to reduce the disproportionate burden of disease in ethnic minorities, critical changes in the current delivery of care to individuals who have diabetes are needed. The necessary changes include a shift from an acute model of care to a chronic disease care model, adoption of patient-centered and collaborative management approaches, and increased health provider and health systems accountability for quality diabetes

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    Dr. Egede is supported in part by grant no. 5K08HS11418 from the Agency for Health Care Research and Quality, Rockville, MD. Dr. Dagogo-Jack is supported in part by National Institutes of Health Clinical Research Center Grant no. MO1 RR00211.

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