Type 2 Diabetes: Risk Factors

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The frequency of diabetes in Hispanic American adults is influenced by the same risk factors that are associated with type 2 diabetes in other populations. Two categories of risk factors increase the chance of developing type 2 diabetes. The first is genetics. The second comprises medical and lifestyle risk factors, including pre diabetes, gestational diabetes, hyperinsulinemia and insulin resistance, obesity, and physical inactivity.

 

Genetic Risk Factors

 

A family history of diabetes increases the chance that people will develop diabetes. The San Antonio Heart Study showed that the prevalence of diabetes among Mexican Americans who have first-degree relatives (e.g., parents) with diabetes was twice as great as for those with no family history of diabetes. Having American Indian or African genes (populations with a high prevalence of diabetes) is also thought to be a factor that causes the higher rates of diabetes in Hispanics. Hispanics, like all populations, inherit their susceptibility to diabetes from their ancestors. Hispanics have three groups of ancestors—Spaniards, American Indians, and Africans. Both American Indians and Africans have high rates of diabetes. Although Cuban Americans have both American Indian and African ancestry, neither of these genetic roots contributes more than 20 percent to the current Cuban American gene pool. This may partly explain why Cuban Americans have a higher prevalence of type 2 diabetes than non-Hispanic white Americans, although not as high as the other Hispanic groups.

 

Medical and Lifestyle Risk Factors

 

Pre-diabetes (Impaired Glucose Tolerance and Impaired Fasting Glucose)

In some people, the blood glucose level is higher than normal, but not enough to be diagnosed as diabetes. These individuals are described as having pre-diabetes. People with pre-diabetes are at higher risk of developing type 2 diabetes than people with normal glucose tolerance. Rates of impaired glucose tolerance among adults ages 40 to 74 in the NHANES III survey were higher for Mexican Americans (19 percent) than for non-Hispanic white Americans (15 percent).

 

Gestational Diabetes

About 2 to 5 percent of pregnant women in the United States develop mild abnormalities in glucose levels, insulin secretion, and insulin resistance and are considered to have gestational diabetes. Although these women's glucose and insulin levels often return to normal after pregnancy, as many as 50 percent may develop type 2 diabetes within 20 years of the pregnancy. Mexican American women may be at particularly high risk for developing type 2 diabetes. One study of 666 women with gestational diabetes in southern California found that each year an average of 12 percent developed type 2 diabetes after pregnancy.

 

Hyperinsulinemia and Insulin Resistance

Hyperinsulinemia (higher than normal levels of fasting insulin) and insulin resistance (an inability to use the body's own insulin to properly control blood glucose) are both hallmarks of an increased risk for developing type 2 diabetes. Hyperinsulinemia often predates diabetes by several years. Among people in the NHANES III survey who did not have diabetes, insulin levels were higher in Mexican Americans than in non-Hispanic whites, indicating their greater predisposition for developing type 2 diabetes. Several other studies have also shown a higher rate of hyperinsulinemia in Hispanics than in non-Hispanics.

 

Obesity

Obesity is a major risk factor for type 2 diabetes. Many racial/ethnic groups in the United States have high rates of obesity, and surveys show that obesity is increasing. Hispanics are more likely than non-Hispanic whites to be overweight. Table 2 shows that Mexican American adults, particularly women, have substantially higher rates of obesity than non-Hispanic white Americans, but rates that are similar to those of African Americans. 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. Mexican Americans with upper body obesity have an increased risk of type 2 diabetes.

 

Table 2.   Prevalence of overweight individuals among whites, blacks and Mexican-Americans in the U.S. Population, 1988-91

 

  Adolescent Adult Men Adult Women
White

21%

32%
33%
Black

27%

31%
49%
Mexican-American

28%

36%
47%

 

Physical Activity

Regular physical activity is a protective factor against type 2 diabetes and lack of activity is a risk factor for developing diabetes. Researchers suspect lack of exercise is one factor contributing to high rates of diabetes in Hispanics. In the NHANES III survey, 65 percent of Mexican American men and 74 percent of Mexican American women reported that they participated in little or no leisure-time physical activity. HHANES data showed that fewer men with high levels of work-related physical activity had diabetes. The San Antonio Heart Study found that decreased leisure physical activity was related to a higher incidence of diabetes.

 

Source: DIABETES from the National Diabetes Clearinghouse

 

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