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Disparities in Diabetes Risk, Cardiovascular Consequences, and Care: Women, Ethnic Minorities, and the Elderly
Disparities in Diabetes Risk
Type 2 diabetes is a growing problem that closely parallels the obesity epidemic and places a severe burden on health care resources in the United States (see also Chapter 1 ). Diabetes currently affects 25.8 million Americans, 8.3% of the United States population, approximately 95% of whom have type 2 diabetes. , The lifetime risk of developing type 2 diabetes for individuals born in 2000 in the United States was estimated to be 32.8% in men and 38.5% in women. Diabetes affects all age, sex, ethnic, and racial groups, but disproportionately affects minority populations, with African Americans and Hispanics having a twofold to threefold increased risk of developing diabetes relative to whites. , Projections indicate that over half of Hispanic women (i.e., 52.5%), almost half of African American women (i.e., 49.0%), and almost one out of every three white women (i.e., 31.2%) will develop diabetes in their lifetime. Projections are slightly lower in men but remain high, with 45.5% of Hispanic men, 40.2% of African American men, and 26.7% of white men projected to develop diabetes during their lifetime.
As the prevalence of diabetes increases, individuals are diagnosed at earlier ages, resulting in greater duration and comorbidity burden and earlier mortality. In African Americans, diabetes diagnosed at age 50 implies living with diabetes for over a quarter of one’s life (i.e., average duration, 18.1 years; 10.1 years of life lost), and diagnosis at 30 implies living with diabetes for almost half one’s life (i.e., average duration, 28.2 years; 17.1 years of life lost). In Hispanics and whites, diagnosis at age 30 similarly implies living with diabetes for over half one’s life (i.e., average duration, 37.7 and 35.3 years, respectively; 14.8 and 13.2 years of life lost, respectively).
From 1980 through 2011, based on information from the National Health Interview Survey (NHIS), , the prevalence of people with self-reported diagnosed diabetes increased by 167% (from 0.6% to 1.6%) for those aged 0 to 44 years, 118% (from 5.5% to 12.0%) for those aged 45 to 64 years, 140% (9.1% to 21.8%) for those aged 65 to 74 years, and 125% (8.9% to 20.0%) for those aged 75 years and older ( Fig. 30-1 ). In general, throughout the time period, the percentage of people with diagnosed diabetes increased among all age groups. In 2011 the percentage of diagnosed diabetes among people aged 65 to 74 (21.8%) was more than 13 times that of people younger than 45 years (1.6%). The NHIS is a health survey of the civilian, noninstitutionalized household population of the United States and has been conducted continuously since 1957 by the National Center for Health Statistics (NCHS), Centers for Disease Control and Prevention (CDC). , In 2011, 63% of the adult incident cases (i.e., cases diagnosed within the previous year) of diabetes were diagnosed in patients between the ages of 40 and 64 years. About 16% were diagnosed in individuals younger than age 40, and approximately 21% were diagnosed in individuals age 65 or older ( Fig. 30-2 ). ,
From 1980 to 1998, the age-adjusted prevalence of self-reported diagnosed diabetes for men and women was similar. However, in 1999 the percentage for men began to increase at a faster rate than the percentage for women. From 1980 to 2011, the age-adjusted percentage of diagnosed diabetes increased from 2.7% to 6.9% for men and from 2.9% to 5.9% for women ( Fig. 30-3 ).
Using data from the NHIS, the incidence of diagnosed diabetes in the United States was estimated from 1997 to 2011 and during this time period the age-adjusted incidence of diagnosed diabetes increased among all racial and ethnic groups and was higher in African Americans and Hispanics than in whites. The age-adjusted incidence of diagnosed diabetes was 12.4/1000 in African Americans, 11.1/1000 in Hispanics, and 7.0/1000 in whites ( Fig. 30-4 ).
Disparities in Cardiovascular Consequences
Diabetes Comorbidities in Racial and Ethnic Minorities
Diabetes is the seventh leading cause of death in the United States. Previous studies report up to a threefold increase in mortality risk associated with diabetes. In the Framingham Heart Study, which included white men and women living in Framingham from 1950 through 1975, the age- and sex-adjusted hazard ratio (HR) associated with diabetes for all-cause mortality was 2.44 (95% confidence interval [CI] 1.99-2.98), whereas the respective HR for the time period 1976 to 2001 was 1.95 (95% CI 1.63-2.33). The age- and sex-adjusted HR for diabetes in non-Hispanic whites in the San Antonio Heart Study, a cohort study of non-Hispanic whites and Mexican Americans living in San Antonio, Texas, is 1.88 (95% CI 1.28-2.77) and is comparable to results from the second time period of the Framingham Heart Study. In contrast, in U.S.-born Mexican Americans in the San Antonio Heart Study, there was a threefold increased risk of mortality associated with diabetes. Unexpectedly, in the San Antonio Heart Study, adjusting for cardiovascular risk factors altered associations only slightly, indicating that the increased mortality risk associated with diabetes in U.S.-born Mexican Americans is independent of cardiovascular risk factors at least to the extent that they were adjusted for.
In the United States, diabetes is a major cause of heart disease and stroke as well as the leading cause of kidney failure, nontraumatic lower-limb amputations, and development of blindness in adults (see also Chapters 7 , 11 , 27 , and 28 ). The incidence of coronary disease is twofold to fivefold higher in those with diabetes relative to those without diabetes , ; the risk of renal failure is twofold higher, the risk of blindness is 20-fold higher, and the risk of lower-extremity amputation is 40-fold higher in those with diabetes relative to those without diabetes. , At the Veterans Health Administration (VHA), diabetes accounts for approximately 50% of cerebrovascular events, 40% of patients with end-stage renal disease receiving dialysis, and over 70% of amputations.
Relative to whites, African Americans with diabetes are at higher risk of complications typically related to hypertension including end stage renal disease, lower-extremity amputation, blindness, and stroke. This is not surprising, given that it is well established that hypertension is more common and less well controlled in African Americans than whites. In studies conducted using the Third National Health and Nutrition Examination Survey (NHANES III), the presence of any diabetic retinopathy lesion was 46% higher in African Americans than in whites, with African Americans also more likely to have moderate or severe retinopathy when compared with whites. End-stage renal disease is a growing problem in the United States, with diabetes accounting for approximately 45% of new patients requiring renal replacement therapy and the incidence of end-stage renal disease increasing more than 80% between 1993 and 2003. Disparities in end-stage renal disease are vast, with incidence rates of 976/million in African Americans and 277/million in whites in 2009, a 3.5-fold higher incidence in African Americans than whites. , Between 1980 and 2008, the age-adjusted incidence of treatment (i.e., dialysis or transplant) for end-stage renal disease in individuals with diabetes varied by race and gender groups ( Fig. 30-5 ). Among individuals with diabetes, the incidence of end-stage renal disease was highest in African American men and lowest in white women. In whites and African Americans with diabetes, the incidence of end-stage renal disease increased in the 1980s, but started to decrease in the 1990s. This can be explained by the increasing incidence of end-stage renal disease in the U.S. population because, although in recent years a lower percentage of individuals with diabetes have developed incident end-stage renal disease, the total number of individuals with diabetes and end-stage renal disease continues to increase. In a study conducted within the Veterans Administration, in which differences in socioeconomic status (SES) and access to care are limited, African Americans with diabetes were also more likely to have nephropathy and end-stage renal disease than whites with diabetes after adjustment for age, sex, and economic status.
Similar to end-stage renal disease, the incidence and prevalence of lower-extremity amputation is higher in African Americans with diabetes than in whites with diabetes. Using age-adjusted hospital discharge rates for nontraumatic lower-extremity amputation, in whites the rates declined from 6.2/1000 individuals with diabetes in 1988 to 2.3/1000 individuals with diabetes in 2009. During the same time period, rates also declined in African Americans, from 6.7/1000 to 4.5/1000 individuals with diabetes, but remained almost twice as high when compared with whites in 2009. In a study conducted within the Veteran Administration, African Americans with diabetes were more likely to undergo a lower-extremity amputation than whites with diabetes.
In contrast to microvascular disease, macrovascular complications, including myocardial infarction and cardiovascular mortality, which are typically related to dyslipidemia, seem to have similar or even lower rates in African Americans with diabetes than whites with diabetes. The similar or even lower rates of heart disease in African Americans may be a result of their distinct but favorable lipid profiles when compared with whites.
Relative to whites, Mexican Americans with diabetes are at higher risk of microvascular as well as macrovascular disease. , In NHANES III, the presence of any diabetic retinopathy lesion was 84% higher in Mexican Americans than whites, with Mexican Americans also more likely to have moderate or severe retinopathy when compared with whites. Rates of end-stage renal disease are also higher in Hispanics than whites. , In 1997, when the United States Renal Data System began collecting information on ethnicity, the age-adjusted incidences of end-stage renal disease were 293.2/100,000 men and 264.1/100,000 women with diabetes (see Fig. 30-5 ). , In 2008, rates had declined to 271.8/100,000 men and 205.8/100,000 women with diabetes. However, in contrast to African Americans, Mexican Americans with diabetes also appear to have increased risk of macrovascular disease relative to whites, although there remains some controversy. , In a study of 827 diabetic San Antonio Heart Study participants, age- and sex-adjusted HRs indicated that U.S.-born Mexican Americans with diabetes had a 70% greater risk of all-cause mortality and a 60% greater risk of cardiovascular mortality than non-Hispanic whites with diabetes. In the San Luis Valley Diabetes Study, of nondiabetic participants, Mexican Americans and whites were at equal risk of incident coronary heart disease (CHD), whereas of diabetic participants, whites were at a higher risk than Mexican Americans of incident CHD. In contrast, a community-based surveillance project, the Corpus Christi Heart Project, reported a higher incidence of hospitalized CHD among Mexican Americans than whites, a higher CHD fatality rate among Mexican Americans than non-Hispanic whites, , and higher community-wide CHD mortality (both in and out of hospital) in Mexican Americans than non-Hispanic whites.
Factors potentially associated with racial or ethnic differences in comorbidity burden include biologic differences in diabetes severity triggered by genetic or environmental factors as well as differences in health care access, treatment practices, and ongoing prevention efforts. Unfortunately, available markers of biologic differences in disease severity including medication use, insulin use, fasting glucose levels, and duration of clinically recognized diabetes are intrinsically tied to health care use and treatment. Increased access to care and disease awareness likely result in a shorter time to recognition and treatment of disease, a higher prevalence of recognized diabetes, a lower prevalence of unrecognized diabetes, and improved outcomes. Duration of diagnosed and duration of undiagnosed diabetes (i.e., time to recognition and treatment) may also be affecting severity and outcomes differently across populations.
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