Epidemiology of Type 2 Diabetes: Focus on Ethnic Minorities
Section snippets
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
References (110)
Current views on obesity
Am J Med
(1996)- et al.
Race and ethnicity determine serum insulin and C-peptide concentrations and hepatic insulin extraction and insulin clearance: comparative studies of three populations of West African ancestry and white Americans
Metabolism
(1997) - et al.
Diabetes in urban African Americans. III. Management of type II diabetes in a municipal hospital setting
Am J Med
(1996) Population-based management of diabetes care
Patient Educ Couns
(1995)- et al.
Quality improvement in chronic illness care: a collaborative approach
Jt Comm J Qual Improv
(2001) National diabetes statistics fact sheet: general information and national estimates on diabetes in the United States. NIH Publication No. 04–3892
(2004)Diagnosis and classification of diabetes mellitus
Diabetes Care
(2005)Diabetes in African Americans. NIH Publication No. 02–3266
(2002)Screening for type 2 diabetes
Diabetes Care
(2004)Executive Summary of the Third Report of the National Cholesterol Education Program (NCEP) Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults (Adult Treatment Panel III)
JAMA
(2001)
Type II diabetes, essential hypertension, and obesity as “syndromes of impaired genetic homeostasis”: the “thrifty genotype” hypothesis enters the 21st century
Perspect Biol Med
Socioeconomic status of obesity: a review of the literature
Psychol Bull
Thrifty genotype: how applicable is it to obesity and type 2 diabetes?
Diabetes Rev
Antagonistic pleiotropy, reversal of dominance, and genetic polymorphism
Am Nat
Complex genetics of type 2 diabetes: thrifty genes and previously neutral polymorphisms
Q J Med
Determinants of diabetes mellitus in the Pima Indians
Diabetes Care
Genetics of diabetes in Nauru: effects of foreign admixture, HLA antigens, and the insulin-gene linked polymorphism
Diabetologia
Non-insulin-dependent diabetes mellitus: a collision between thrifty genes and affluent society
Ann Med
Diabetes in Asian and Pacific Islander Americans
Noninsulin-dependent diabetes mellitus in black and white Americans
Diabet Metab Rev
Does obesity explain excess prevalence of diabetes among Mexican Americans? Result of the San Antonio Heart Study
Diabetologia
Reduction in the incidence of type 2 diabetes with lifestyle intervention or metformin
N Engl J Med
Insulin resistance as the core defect in type 2 diabetes mellitus
Am J Cardiol
Insulin resistance and insulin secretory dysfunction are independent predictors of worsening of glucose tolerance during each stage of type 2 diabetes development
Diabetes Care
Pathogenetic mechanisms of impaired glucose tolerance and type II diabetes in African-Americans
Diabetes Care
Increased insulin resistance and insulin secretion in nondiabetic African-Americans and Hispanics compared with non-Hispanic whites
Diabetes
Physical and metabolic characteristics of persons with diabetes
The effect of intensive treatment of diabetes on the development and progression of long-term complications in insulin-dependent diabetes mellitus
N Engl J Med
Intensive blood-glucose control with sulfonylurea or insulin compared with conventional treatment and risk of complications in patients with type 2 diabetes (UKPDS 33)
Lancet
Is the risk of diabetic retinopathy greater in non-Hispanic blacks and Mexican Americans than in non-Hispanic whites with type 2 diabetes? A US population study
Diabetes Care
Physician and patient preventive practices in NIDDM in a large urban managed-care organization
Diabetes Care
Lifestyle modification to improve blood pressure control in individuals with diabetes: is physician advice effective?
Diabetes Care
Diabetes in African Americans
Diabetes in America
Comparison of laboratory test frequency and test results between African-Americans and caucasians with diabetes: opportunity for improvement
Diabetes Care
Racial and ethnic differences in health care access and health outcomes for adults with type 2 diabetes
Diabetes Care
Diabetes in urban African-Americans. 1. Cessation of insulin therapy is the major precipitating cause of diabetic ketoacidosis
Diabetes Care
Ethnic disparities in diabetic complications in an insured population
JAMA
A diabetes report card for the United States: quality of care in the 1990s
Ann Intern Med
Racial/ethnic differences in adult vaccination among individuals with diabetes
Am J Public Health
Racial/ethnic differences in influenza vaccination coverage in high-risk adults
Am J Public Health
Association between number of physician visits and influenza vaccination coverage among diabetic adults with access to care
Diabetes Care
Ambulatory medical care for non-Hispanic whites, African-Americans, and Mexican-Americans with NIDDM in the US
Diabetes Care
Quality of outpatient care provided to diabetic patients
Diabetes Care
Quality of medical care delivered to Medicare beneficiaries: a profile at state and national levels
JAMA
The economic costs of non-insulin-dependent diabetes mellitus
JAMA
Comparing the national economic burden of five chronic conditions
Health Aff (Millwood)
Economic consequences of diabetes mellitus in the US in 1997
Diabetes Care
Economic costs of diabetes in the US in 2002
Diabetes Care
UK Prospective Diabetes Study (UKPDS). VIII. Study design, progress and performance
Diabetologia
Cost effectiveness of an intensive blood glucose control policy in patients with type 2 diabetes: economic analysis alongside randomised controlled trial (UKPDS 41). United Kingdom Prospective Diabetes Study Group
BMJ
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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.