Epidemiology

SCOPE OF THE PROBLEM

In 2007, the Center for Disease Control in the United States estimated that diabetes affects approximately 23.6 million children and adults or 8% of the US population. An estimated one third is unaware that they have the disease. An additional 57 million people who are prediabetic will become diabetic if they do not change their eating habits.¹ Diabetes is the fifth most common cause of death in America. In one study, 18% of the hospital admissions were found to have unrecognized and probable diabetes by the criteria of elevated HbA1c (>6.1).²

From 1990 to 2005, the prevalence of diabetes increased from 4.5 to 26.4 per 1,000 people, a sixfold increase. Researchers postulated that this increase was due to the increase in obesity during 1990–2005.³ One study shows that currently 4% of obese white adolescents have diabetes and an additional 21% have abnormal glucose tolerance.⁴

In 2007, the economic cost of diabetes was estimated to be $174 billion.¹ Health care and medical expenditures related to diabetes totaled $116 billion (Table 1-1). Of that amount, $27 billion was for diabetes care, $31 billion for extra general medical costs, and $58 billion for chronic diabetic complications. People with diabetes had medical expenses that were 2.3 times higher than those for people without diabetes. Diagnosed diabetic patients accounted for 5.8% of the total US population. Inpatient hospital care accounted for $58.3 billion. For physician office visits, $9.9 billion was spent in 2007. Diabetes accounted for 24.3 million days of hospitalizations in 2007, whereas in 2002, that figure was 16.9 million days. In 2007, average cost for a hospital inpatient day due to diabetes was $1853 and $2281 due to diabetes-related chronic complications including neurological, peripheral-vascular, cardiovascular, renal, metabolic, and ophthalmic complications.

The indirect costs were estimated to $58 billion in 2007.¹ In 2007, diabetes accounted for 15 million work days of absence, 120 million work days with reduced performance, 6 million reduced productivity days for those not in the workforce, and an additional 107 million work days lost due to unemployment disability attributed to diabetes. Diabetes costs 445,000 cases of unemployment disability in 2007. The value of lost productivity due to premature death related to diabetes was $26.9 billion.

The increase in cost due to diabetes is related to (a) the growth of diabetes prevalence, (b) medical costs rising faster than general inflation, and (c) improvements made in the methods and data sources influencing cost estimates. The national burden of diabetes likely exceeds the $174 billion estimate because it omits the social cost of intangibles such as pain and suffering, care provided by nonpaid caregivers, excess medical costs associated with undiagnosed diabetes, and diabetes-attributed costs for health care expenditures categories not studied.¹

Thus, the indirect cost of $58 billion dollars is from increased absenteeism, reduced productivity, disease-related unemployment disability, and loss of workplace productivity.¹ This $58 billion cost in 2007 eclipsed the $16 billion for the same problems in 2002. The reason for the increase is due to the obesity epidemic among teens. One out of every five health care dollars is spent caring for a diabetic patient, whereas 1 in 19 health care dollars is spent for the treatment of diabetes and its complications.⁵

LIFETIME RISK FOR DIABETES MELLITUS IN THE UNITED STATES

Data from the National Health Interview Survey (1984–2000) show that the estimated lifetime risk of developing diabetes for individuals born in 2000 is 32.8% for males and 38.5% for females. Females have the higher residual lifetime risks for all age groups. The highest estimated lifetime risk for diabetes is among Hispanics (males 45.4% and females 52.5%). Individuals diagnosed as having diabetes have a large reduction in life expectancy. If a person is diagnosed at age 40, men will lose 11.6 life years and 18.6 quality-adjusted life years and women will lose 14.3 life years and 22.0 quality-adjusted life years. Thus, primary prevention of diabetes and its complications is an important public health priority.⁶

MEDICAL CARE FOR DIABETIC PATIENTS

In the 1989 National Health Interview Survey, 84,572 adults 18 years and older were studied. From this group, a subgroup of diabetic patients, 2,405 respondents, were queried about their diabetes care. More than 90% of the diabetic adults had one physician for the usual care of their diabetes, but 32% made fewer than four visits to the physician each year. Most physician visits by diabetic patients were not made to diabetes specialists. The visit rate to nonprimary care physicians such as other health care professionals such as ophthalmologists, podiatrists, nutritionists, was low. About half of the insulin-treated diabetic subjects used multiple daily insulin injections. Forty percent of patients with insulin-dependent diabetes and 26% with non–insulin-dependent diabetes mellitus (NIDDM) took insulin, and 5% of NIDDM patients not taking insulin monitored their blood glucose daily. Diabetes patient education classes were attended by 35% of diabetic adults. Thus, there is a need for specialists who treat diabetic patients.⁷

RACE AND ETHNIC DIFFERENCES

The association between impaired glucose tolerance (IGT) and the risk of Type 2 diabetes has been documented in a wide range of racial and ethnic groups (Table 1-2). In the San Antonio Heart Study, the relative risk of developing Type 2 diabetes conferred by IGT ranges from 4.3 to 7 depending upon race and gender.⁸

Native Americans

The 2005 Indian Health Service User population database indicated that 14.2% of American Indians and Alaskan Natives (AI/AN) aged 20 or older were diabetic. Rates varied from 6.0% in Alaska Native adults to 29.3% among American Indian adults in Southern Arizona. In this study, diabetes occurred in 6.6% non-Hispanic whites, 7.5% Asian Americans, 10.4% Hispanics, and 11.8% non-Hispanic blacks.⁹ In another study, American and Alaskan Native children (<15 years), adolescents (15–19 years), and young adults (20–34 years) had a 71% increase in diagnosis of diabetes. Diabetes prevalence increased by 46% from 1990 to 1998 in the above three groups.¹⁰

African Americans

In 1993, 1.3 million African Americans were known to have diabetes. This figure is almost three times the number of African Americans with diabetes in 1963. The actual number of diabetic African Americans is probably higher since there are many undiagnosed with the disease than reported. It is thought that for every African American diagnosed with diabetes, there is another African American yet to be diagnosed or who does not know that he or she has the disease. From 1980 to 2005, the age-adjusted prevalence of diagnosed diabetes doubled among black males and increased 69% among black females. However, of all groups observed, black females had the highest overall prevalence.¹¹

After the 2000 census, it is known that 11% or 2.7 million of African Americans, aged 20 or older, have diabetes. One third of these do not even know that they have the disease. African Americans are 1.6 times more likely than white Americans to get diabetes.

One out of every four African American women is diabetic if they are 55 years or older. Twenty-five percent of blacks between the ages of 65 and 74 have diabetes.¹² Of note, African Americans are twice as likely to develop diabetic retinopathy than their white counterparts.¹³

In 1993, for the age group of 65 to 74 years, 17.4% of blacks were diabetic versus 9.5% of white Americans.¹³ African Americans had a greater incidence of Type 2 diabetes. In fact, prevalence of Type 1 diabetes in white American children aged 15 and younger was nearly twice as that in African American children of the same age.¹³ At age 45 and older, the prevalence of diabetes was 1.4 to 2.3 times as frequent in blacks as in whites. Within the age group of 65 to 74 years, 17.4% of blacks had diagnosed diabetes versus 9.5% of whites.

While gestational diabetes, which affects 2% to 5% of all pregnant women, usually resolves after childbirth, African American women have a higher rate of gestational diabetes. An Illinois study has shown an 80% higher incidence of gestational diabetes in black women as compared to their white counterparts. Experts estimate that about half of the women with gestational diabetes develop Type 2 diabetes within 20 years of pregnancy, regardless of race.¹³

African Americans may have a hemoglobin variant. Thus, the HbA1c of African Americans may not be accurate, falsely low or high, thus, it is important to check with the clinical laboratory to correlate the hemoglobin A1c with the patient’s hemoglobin variant. African Americans have hemoglobin variants such as Hemoglobin S, Hemoglobin C, or Hemoglobin E.¹⁴

Latino Americans

Two in five Hispanics born in the year 2000 face a risk for diabetes. Compared to whites, Hispanics are more than two times as likely to have diabetes. From 1997 to 2005, the age-adjusted prevalence among Hispanics increased 16% among males and 21% among females.

In one study, the Hispanic population, which is the second largest and fastest growing minority in the United States, shares genetic markers with Americans, the Spanish, and Africans. The high frequency of Native American–derived genes in the contemporary Hispanic population predicts a higher frequency of NIDDM. The genetic markers, taken from 1,000 randomly selected Mexican Americans from Starr County, Texas, are used as a representative sample of the Mexican American population. For Mexican Americans, 31% of the contemporary gene pool is estimated to be Native American derived whereas 61% and 8% are Spanish and African derived, respectively. In Puerto Rico, the percentage of contributions of Spanish, Native American, and African mixture to the population are 15%, 18%, and 37%, respectively. In Cuba, the parallel estimates are 62%, 18%, and 20%. The high frequency of Native American-derived genes in contemporary Hispanic population predicts a higher frequency of NIDDM under the assumption that NIDDM may have genetic markers.¹⁵

Two million Latinos, aged 20 or older, have Type 1 or Type 2 diabetes. Latinos are 1.5 times more likely than non-Hispanic whites to have Type 2 diabetes, but Latinos are 2 times more likely than non-Hispanic whites to have any type of diabetes, Type 1 or Type 2. Specifically, Mexican Americans are 1.7 times more likely and Puerto Ricans are 1.8 times more likely to develop Type 2 diabetes than whites. Twenty-five percent to thirty percent of Hispanics older than age 50 have diabetes. Latinos are the fastest growing minority group in the United States. However, they have the lowest rates of insurance coverage and without regular and proper health, health care, and health care follow-up, diabetes can progress to blindness. Nearly half of the Latino children born in 2000 are likely to develop diabetes in their lifetime.¹⁶

Asian Americans

Diabetes is rising faster in Asian Americans than Caucasians. The rate among Asian Americans is 10% to 15% versus 6% to 8% ian>n Caucasians.⁹ These rates are similar to that found in Hong Kong.¹⁶ The International Diabetes Federation predicts that diabetic rate in Asia are expected to rise to 160 million by 2025. India and China would account for 120 million by 2025.¹⁶

Top five countries with largest number of people affected by diabetes in 2003:

India—35.5 million

China—23.8 million

class United States—16 million (by 2008, 21 to 23 million)

Russia—9.7 million

Japan—6.7 million

Ninety to ninety-five percent of Asians with diabetes have Type 2 diabetes. The rate of diabetes in Chinese Americans is notably higher than the rate of Chinese population in rural China. Thus, there are environmental factors that play a role in the development of diabetes in Chinese Americans in the United States. Indo-Asian women in America have the highest gestational diabetes rate in the country, with a prevalence of 56.1 per 100,000.¹⁷ Native Hawaiians are 2.5 times likely to have diabetes than their white counterparts.¹⁸ When Asians immigrate to the United States, their risk of developing diabetes increases significantly. This is most probably due to a change in lifestyle, diet, and exercise.¹⁹

Native Americans

AI/AN are people who have origins in any of the original peoples of North and South America including Central America and who maintain a tribal affiliation or community attachment. According to the 2000 US Census, those who identify as AI/AN constitute 0.9% of the US population or 2.5 million individuals. The greatest concentration of AI/AN populations are in the West, Southwest, and Midwest, especially in Alaska, Arizona, Montana, New Mexico, Oklahoma, and South Dakota. There are 569 federally recognized AI/AN tribes, plus an unknown number of tribes that are not federally recognized. Each tribe has its own culture, beliefs, and practices. Among people younger than age 20, American Indians aged 10 to 19 years have the highest prevalence of Type 2 diabetes.²⁰ Gestational diabetes occurs more frequently among American Indians who are thought to have a high incidence of obesity during pregnancy. The risk factors for gestational diabetes include obesity and women with a family history of diabetes (Table 1-3).

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