Asian and Pacific Islander Americans and Diabetes

Diabetes mellitus poses a rapidly growing health challenge to Asian and Pacific Islander Americans in the United States. In 1997, the Asian and Pacific Islander American (APIA) population was estimated to be about 10 million, almost a 50 percent increase since the 1990 Census and representing about 3.8 percent of the total U.S. population.¹ This group includes people whose origins are in the Far East, Southeast Asia, the Indian subcontinent, and the Pacific Islands.² Results of the 1990 Census showed that the APIA population had the greatest increase of any major ethnic group, doubling in size since the 1980 Census.³ The Immigration Act of 1965 and the arrival of many Southeast Asian refugees under the Refugee Resettlement Program after 1975 contributed to the increase in population observed in the past two decades.

Asian and Pacific Islander Americans in the United States were classified into 28 Asian and 19 Pacific Islander ethnic groups for the 1990 U.S. Census (see table 1). These populations include people whose families originated in a variety of countries, providing great diversity in language, culture, and beliefs. Nearly 75 percent are foreign-born, but other members of this group are fifth-generation Asian-Americans.⁴

The 1990 Census showed that 56 percent of the APIA population lived in the western States. Seventy-three percent were located within seven States: California, Hawaii, Illinois, New Jersey, New York, Texas, and Washington.³

Table 1.
Asian and Pacific Islander ethnicities in the United States.

Diabetes mellitus is a group of diseases characterized by high blood levels of glucose. It results from defects in insulin secretion, in insulin action, or both. Diabetes can be associated with serious complications and premature death, but people with diabetes can take measures to reduce the likelihood of these occurrences.

Most Asian and Pacific Islander Americans with diabetes have type 2 diabetes. This type usually develops in adults, but it can also develop in children or adolescents. It is caused by the body's resistance to the action of insulin and by impaired insulin secretion. It can be managed with healthy eating, physical activity, oral diabetes medications, and/or injected insulin. Until recently, type 2 diabetes was rarely diagnosed in children and adolescents. However, recent reports highlight an increasing incidence of type 2 diabetes in children and adolescents. A small number of Asian and Pacific Islander Americans have type 1 diabetes, which usually develops before age 20 and is managed with insulin, healthy eating, and physical activity.

Diabetes can be diagnosed by three methods⁵:

• A casual (random) plasma glucose value of 200 milligrams per deciliter (mg/dL) or greater in people with symptoms of diabetes.
• A fasting plasma glucose test with a value of 126 mg/dL or greater.
• An abnormal oral glucose tolerance test with a 2-hour glucose value of 200 mg/dL or greater.

Each test must be confirmed, on another day, by any of the above methods.

How Many Asian and Pacific Islander Americans Have Diabetes?

Type 2 Diabetes

Prevalence data for Asian and Pacific Islander Americans are limited, but studies have shown that some groups within this population are at increased risk for developing type 2 diabetes compared with non-Hispanic white people in the United States. Table 2 shows how prevalence in several studies was higher for selected Asian Americans and Pacific Islander Americans than for non-Hispanic white people.

Table 2.
Prevalence of diabetes in the United States in non-Hispanic white people, Asian Americans, and Native Hawaiians.

A study of the prevalence of diabetes and glucose intolerance was recently conducted among Native Hawaiians in two rural communities. Results showed a 22.4 percent age-standardized prevalence of type 2 diabetes in people age 30 or older. Prevalence was highest in people age 60 to 64 who had a rate of 40 percent. This prevalence was four times higher than that of the non-Hispanic white population surveyed in the U.S. National Health and Nutrition Examination Survey II.⁹ Analysis of data collected in Hawaii from 1988 to 1995 showed that Native Hawaiians had double the rate of diagnosed diabetes that non-Hispanic white residents had.¹⁰

In contrast, the prevalence of diabetes in some isolated Polynesian groups is relatively low. For example, in 1976 in Funafuti, Tuvalu, the prevalence was 1.1 percent in men and 7.2 percent in women. Researchers attributed the difference in rates to differences in physical activity. In that community, men were engaged in manual labor, but women were sedentary and consumed more calories than needed for their level of activity.³

In Western Samoa, diabetes prevalence in a rural community (3.4 percent) was less than half the rate in an urban setting (7.8 percent), even after adjusting for body weight. Rural residents were much more active physically than their urban counterparts.³

Recent reports in the literature highlight an increasing incidence of type 2 diabetes in youth, particularly in members of minority groups. Data about APIA youth are scarce, but trends among Asian youth may indicate future trends in the larger group. For example, studies of Japanese school children in Japan show a dramatic increase in the incidence of type 2 diabetes. Incidence in 1976 was 0.2 per 100,000 children; incidence in 1995 was 7.3 per 100,000. Junior-high-age children had an incidence of 13.9 per 100,000, which was nearly 7 times the rate of type 1 diabetes in the same group. Researchers attribute the increase in incidence to changes in food habits and rising rates of obesity.¹¹

Type 1 Diabetes

Type 1 diabetes in Asian children is relatively rare; rates are significantly lower than those among non-Hispanic whites. Data from one study suggested that environmental factors might be involved in the etiology of type 1 diabetes, since rates in Japanese children in Hawaii were higher than rates of type 1 diabetes in Japanese children in Tokyo.³

What Risk Factors Increase the Chance That Asian and Pacific Islander Americans Will Develop Type 2 Diabetes?

Two categories of risk factors increase the chance of type 2 diabetes. The first is genetics. The second is medical and lifestyle factors, including obesity, diet, and physical inactivity. Individuals with impaired glucose tolerance, impaired fasting glucose, or insulin resistance are at higher risk of progressing to diabetes.

Genetic Risk Factors

Genetic background is a determining factor in the prevalence of type 2 diabetes. Few data exist on specific genetic causes in the APIA population, but some researchers have suggested that the "thrifty gene" theory may be involved in the increased prevalence of diabetes in some minority populations, particularly those with high rates of obesity. The thrifty gene theory, first proposed in 1962, suggests that population groups who experienced alternating periods of feast and famine gradually adapted by developing a way to store fat more efficiently during periods of plenty to better survive famines.

Lifestyle and MedicalRisk Factors

• Obesity
  

  Obesity is a major risk factor for type 2 diabetes among all races and ethnic groups. The degree to which obesity is a risk factor for diabetes depends not just on overall weight, but also on the location of the excess weight. Central or upper-body obesity is a stronger risk factor for type 2 diabetes than excess weight carried below the waist.³ In a study comparing Japanese people in Japan with Japanese people who had emigrated to Hawaii, the Hawaiian Japanese had a higher rate of obesity and double the prevalence of type 2 diabetes.⁸ The sharp increase in type 2 diabetes in youth has paralleled the dramatic increase of obesity in youth.¹¹

• Diet and Physical Inactivity
  

  As a result of migration and modernization, the food choices of some members of APIA subgroups have changed. Many of the APIA populations have abandoned a traditional plant- and fish-based diet and are choosing foods with more animal protein, animal fats, and processed carbohydrates. One study compared the dietary content of similarly aged Japanese-American men living in Seattle, Washington, with that of Japanese men in Japan. The Japanese-American diet was higher in calories, protein, fat, and carbohydrates. The mean daily intake of fat in Japanese-American men was 32.4 grams, in contrast to a mean intake of only 16.7 grams of fat in Japanese men.³ Other studies have shown that, for many Asian Americans, their diet in America is higher in calories and fat and lower in fiber than in their countries of origin.⁸

  Most studies have shown lower rates of physical activity in minorities than in non-Hispanic whites in the United States.⁸ With the increase in migration and urbanization, physical activity has been greatly reduced in the APIA population. Urbanization has caused this population to change from a lifestyle characterized by hard labor to a more sedentary one.³

  Findings in a study of 8,000 Japanese-American men living in Hawaii suggested that a Japanese lifestyle was associated with a reduced prevalence of type 2 diabetes. Components of this lifestyle included higher levels of physical activity and consumption of more carbohydrates and less fat and animal protein.¹²

• Impaired Glucose Tolerance and Impaired Fasting Glucose
  

  Recent recommendations describe two categories of the physiological state between normal blood glucose and the diabetic range of blood glucose. Individuals are described as having impaired glucose tolerance (a 2-hour glucose value of between 140 and 199 mg/dL during the oral glucose tolerance test) or impaired fasting glucose (a fasting plasma glucose value of between 110 and 125 mg/dL).⁵

  Asian Americans have shown higher rates of impaired glucose tolerance than have non-Hispanic whites in a number of studies.⁸ The prevalence of impaired glucose tolerance among Native Hawaiians in a recent study was 15.6 percent; prevalence rates were constant across age groups.⁹

• Hyperinsulinemia and Insulin Resistance
  

  Hyperinsulinemia (higher than normal levels of fasting insulin) and insulin resistance (the inability of the body to use its own insulin to properly control blood glucose) are both associated with an increased risk of developing type 2 diabetes. Hyperinsulinemia often predates diabetes by several years. These factors, possibly linked to the APIA population through genetics and obesity, increase the risk of developing type 2 diabetes.³

How Does Diabetes Affect Asian and Pacific Islander American Women During Pregnancy?

Gestational diabetes, in which blood glucose levels are elevated above normal during pregnancy, occurs in about 2 to 5 percent of all American pregnant women. Perinatal problems such as macrosomia (large body size) and neonatal hypoglycemia (low blood sugar) are higher in babies born to women with gestational diabetes. Although blood glucose levels generally return to normal after childbirth, an increased risk of developing gestational diabetes in future pregnancies remains. In addition, studies show that many women with gestational diabetes will develop type 2 diabetes later in life. Asian-American women seem to have rates of gestational diabetes that are similar to those of non-Hispanic white women in the United States.⁸

How Does Diabetes Affect Cardiovascular Health in Asian and Pacific Islander Americans?

Diabetes is a major risk factor for cardiovascular disease; data suggest that minorities in general have a rate of risk for this disease similar to that of the non-Hispanic white population. Both impaired glucose tolerance and type 2 diabetes were risk factors for coronary artery disease among Japanese Americans in a Seattle study.⁸ Although data on the relationship of stroke and hypertension to diabetes in this population are limited, ischemic heart disease is one of the leading causes of death for both men and women.²

How Do Diabetes Complications Affect Asian and Pacific Islander Americans?

Diabetic Retinopathy

Diabetic retinopathy is a deterioration of the blood vessels in the eye caused by high blood glucose levels. It can lead to impaired vision and, ultimately, to blindness. In general, age-standardized rates of blindness from diabetes for nonwhites are double those for non-Hispanic whites. However, no data on Asian and Pacific Islander Americans are available.⁸

Diabetic Nephropathy

Minority groups in general have higher rates of end-stage renal disease related to diabetes than do non-Hispanic white people. Among the minority groups, Asian Americans and Pacific Islanders have the lowest prevalence of end-stage renal disease. Minorities have better survival rates after treatment with dialysis than do non-Hispanic white people.⁸

Lower Extremity Amputation

There are no published reports on the rate of amputations among this population.⁸

Does Diabetes Cause an Inordinate Number of Deaths in Asian and Pacific Islander Americans?

Because mortality rates are based on the underlying cause of death on death certificates, the impact of diabetes on mortality among Asian and Pacific Islander Americans has been underestimated.

For APIA populations as a whole, diabetes ranked as the fifth-highest cause on death certificates for people between 45 and 64. Among non-Hispanic whites, diabetes is the seventh leading cause of death. However, the age-adjusted mortality rate for Asian and Pacific Islander Americans from diabetes is 12.4 per 100,000, which falls below the rate of 15.9 per 100,000 for non-Hispanic white Americans. The APIA rate is well below rates for other minority populations (African American, 35.7; American Indian and Alaska Native, 30.3; and Hispanic American, 28.3).²

A review of death records in American Samoa for the years 1962 to 1974 showed that the age-adjusted, diabetes-related mortality rate for Samoa was more than double that of the United States.³

How Is NIDDK Addressing the Problem of Diabetes in Asian and Pacific Islander Americans?

Diabetes Prevention Program

In 1996, NIDDK launched its Diabetes Prevention Program (DPP). The goal of this research effort was to learn how to prevent or delay type 2 diabetes in people with impaired glucose tolerance (IGT), a strong risk factor for type 2 diabetes.

The findings of the DPP, which were released in August 2001, showed that people at high risk for type 2 diabetes could sharply lower their chances of developing the disease through diet and exercise. In addition, treatment with the oral diabetes drug metformin also reduced diabetes risk, though less dramatically. These results were so striking that the DPP's external data monitoring board advised ending the trial early.

Participants randomly assigned to intensive lifestyle intervention reduced their risk of getting type 2 diabetes by 58 percent. On average, this group maintained their physical activity at 30 minutes per day, usually with walking or other moderate intensity exercise, and lost 5 to 7 percent of their body weight. Participants randomized to treatment with metformin reduced their risk of getting type 2 diabetes by 31 percent.

Of the 3,234 participants enrolled in the DPP, 45 percent were from minority groups that suffer disproportionately from type 2 diabetes: African Americans, Hispanic Americans, Asian Americans and Pacific Islanders, and American Indians. The trial also recruited other groups known to be at higher risk for type 2 diabetes, including individuals age 60 and older, women with a history of gestational diabetes, and people with a first-degree relative with type 2 diabetes. Participants ranged from age 25 to 85, with an average age of 51.

Lifestyle intervention successfully reduced the risk of getting type 2 diabetes for both men and women, and across all the ethnic groups. It reduced the development of diabetes in people age 60 and older by 71 percent. Metformin was also effective in men and women and in all the ethnic groups, but was relatively ineffective in the older volunteers and in those who were less overweight.

Researchers will continue to analyze the data to determine whether the interventions reduced cardiovascular disease and atherosclerosis, major causes of death in people with type 2 diabetes. The DPP is the first major trial to show that diet and exercise can effectively delay diabetes in a diverse American population of overweight people with IGT.

NIDDK and the Centers for Disease Control and Prevention are jointly sponsoring the National Diabetes Education Program (NDEP). Its goal is to reduce the death and disability associated with diabetes and its complications. NDEP conducts ongoing diabetes awareness and education activities for people with diabetes and their families. Special efforts are being made to address the needs of the ethnic groups that are hardest hit by diabetes, including African Americans, Alaska Natives, American Indians, Asian and Pacific Islander Americans, and Hispanic Americans. Through these efforts, NDEP hopes to improve the treatment and outcomes for people with diabetes, promote early diagnosis, and, ultimately, prevent the onset of diabetes.

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