Medical care for patients with diabetes. Epidemiologic aspects

OBJECTIVE

To describe the epidemiologic characteristics of physician care and self-care for adults with diabetes in the U.S. population.

DESIGN AND SUBJECTS

Data are drawn from the 1989 National Health Interview Survey, in which a personal household interview was administered to a representative sample of U.S. adults aged 18 years or older. The response rate was 96% (n = 84,572). All subjects identified as having diabetes previously diagnosed by a physician were asked a series of questions about their diabetes. Response rate for this representative sample of U.S. diabetic patients was 95% (n = 2405).

MEASUREMENTS

Self-reported information was obtained about various aspects of diabetes care, including care by physicians and self-case practices of the diabetic persons. Sociodemographic and clinical factors that may influence diabetes care were also determined.

RESULTS

More than 90% of diabetic adults had one physician for the usual care of their diabetes, but 32% made fewer than four visits to this physician each year. Most physician visits by diabetic patients were not made to diabetes specialists, and the visit rate to other health care professionals such as ophthalmologists, podiatrists, and nutritionists was low. About half of insulin-treated diabetic subjects used multiple daily insulin injections; and 40% of patients with insulin-dependent diabetes mellitus, 26% of those with non-insulin-dependent diabetes mellitus (NIDDM) who were taking insulin, and 5% of those with NIDDM who were not taking insulin monitored their blood glucose level daily. Diabetes patient education classes had been attended by 35% of diabetic adults.

CONCLUSIONS

These and other data indicate that medical care for diabetic patients and their self-care practices may not be optimal for prevention of diabetes complications. The Diabetes Control and Complications Trial showed that achieving and maintaining near-normal glycemia, with a concomitant 50% to 70% reduction in diabetes complications, may require close monitoring and ongoing support from a health care team, ample financial resources, and advanced patient knowledge and motivation. Providing this level of diabetes management to all diabetic persons may require major changes in the health care system and in patient self-care practices.

Impaired glucose tolerance--prevalence and conversion to NIDDM

Impaired glucose tolerance (IGT) has been investigated in a large number of populations from different parts of the world and with differing lifestyles. The occurrence of IGT varies widely. IGT prevalence tends to increase with age, but there is no consistent relationship with gender. Prevalence is lower in groups with less obesity and having physically active lifestyles, such as those living in rural areas and having traditional lifestyles, even when subjects with the same genetic background are compared. Risk factors for IGT are similar to those for non-insulin dependent diabetes mellitus (NIDDM). IGT, characterized by hyperglycaemia and insulin resistance, is probably a stage in the pathogenesis of NIDDM. Therapies aimed at improving glucose tolerance and decreasing insulin resistance in subjects with IGT may, therefore, be able to delay or prevent the development of NIDDM.

Epidemiologic studies on the pathogenesis of non-insulin-dependent diabetes mellitus (NIDDM)

The diagnostic criteria of the US National Diabetes Data Group and the World Health Organization have stimulated a major increase throughout the world in epidemiologic studies on the pathogenesis of non-insulin-dependent diabetes mellitus (NIDDM). They have established that much of NIDDM is undiagnosed, that onset of NIDDM occurs at least 7 y before its diagnosis, and that significant morbidity and premature mortality occur in subjects with undiagnosed diabetes. New studies have shown that rural or traditional-living populations are experiencing a major increase in the burden of NIDDM as they move to urban or nontraditional situations, often with 5- to 10-fold increases in NIDDM prevalence. Epidemiologic studies have documented that major risk factors for NIDDM include increasing age, greater obesity, longer duration of obesity, unfavourable body fat distribution, physical inactivity, and hyperinsulinemia. All these factors interact with unknown genetic factors to produce NIDDM. Studies have shown that genes for diabetes, as yet undetermined, are a necessary cause of NIDDM. Hyperinsulinemia exists in childhood in populations at high risk for NIDDM. Stimulated by obesity, upper body obesity, and physical inactivity, insulin resistance develops, accompanied by impaired glucose tolerance. The pressure of the NIDDM risk factors continues this process of insulin resistance/hyperinsulinemia/hyperglycemia, until glucose toxicity to the beta cell results in inability to secrete sufficient insulin, resulting in decompensated fasting hyperglycemia.

Racial/ethnic differences in age-related maculopathy. Third National Health and Nutrition Examination Survey

PURPOSE

To investigate the prevalence of age-related maculopathy in three racial/ethnic groups, non-Hispanic whites, non-Hispanic blacks, and Mexican Americans.

METHODS

People 40 years of age or older who participated in a nationally representative population-based sample of the Third National Health and Nutrition Examination Survey were examined from 1988 to 1991. Age-related maculopathy was determined by grading of fundus photographs using a standardized protocol for a sample of 4007 persons.

RESULTS

The prevalence of any age-related maculopathy in the civilian noninstitutionalized United States population including those 40 years of age or older was 9.2% as estimated from the sample. Prevalence was higher in non-Hispanic whites (9.3%) compared with non-Hispanic blacks (7.4%) and Mexican Americans (7.1%). Before 60 years of age, Mexican Americans (odds ratio [OR], 1.53; 95% confidence interval [CI] 1.0-2.35) and non-Hispanic blacks (OR, 1.59; 95% CI, 0.86-2.95) had a greater chance of having any maculopathy than non-Hispanic whites; thereafter, Mexican Americans (OR, 0.63; 95% CI, 0.44-0.90) and non-Hispanic blacks (OR, 0.50; 95% CI, 0.37-0.68) had a lesser chance than non-Hispanic whites.

CONCLUSION

These survey data indicate that age-related maculopathy is prevalent in all groups studied. Differences among the racial/ethnic groups vary by age and sex.

Prevalence of adult-onset IDDM in the U.S. population

OBJECTIVE

To investigate the prevalence of adult-onset insulin-dependent diabetes mellitus (IDDM) in a nationally representative sample of adults 30-74 years of age. Although it is a widely held belief that onset of IDDM in adults is rare, there are few objective data to support this. Adult-onset IDDM may represent a disease that is biologically distinct from youth-onset IDDM, and it would be important to distinguish these two entities.

RESEARCH DESIGN AND METHODS

The Second National Health and Nutrition Examination Survey (NHANES II) contained a national probability sample of 12,102 subjects 30-74 years of age in the U.S. population. All subjects with diabetes diagnosed by a physician before the survey were identified. Cases of IDDM defined by age at diagnosis > or = 30 years, continuous or nearly continuous insulin treatment since diagnosis of diabetes, and relative body weight < or = 125 were classified as adult-onset IDDM.

RESULTS

Subjects with adult-onset IDDM represented 0.30% of the U.S. population 30-74 years of age and 7.4% of all diabetic patients diagnosed at 30-74 years of age.

CONCLUSIONS

These data indicate that onset of IDDM in adults is uncommon. Given the limitations of the survey instrument, subclinical or slowly progressive IDDM (as distinguished from non-insulin-dependent diabetes mellitus with progressive loss of beta-cell function) would not have been detected, and these would constitute additional cases of adult-onset IDDM. However, the data suggest that a very large population base would be required to identify sufficient numbers of adult-onset IDDM cases for study of the etiology and pathogenesis of this disease.

Frequency and determinants of screening for diabetes in the U.S

OBJECTIVE

To determine the prevalence of risk factors for non-insulin-dependent diabetes mellitus (NIDDM) and the frequency of screening for NIDDM in U.S. adults.

RESEARCH DESIGN AND METHODS

A detailed questionnaire was administered to a representative sample of 19,680 adults > or = 18 years of age who reported no medical history of diabetes in the 1989 National Health Interview Survey (NHIS). Information was obtained on risk factors for diabetes, complications related to diabetes, and whether the subjects had been screened for diabetes in the past year. Women reporting pregnancy in the past year were excluded from analysis. The prevalence of undiagnosed NIDDM according to the frequency of risk factors for NIDDM was determined based on oral glucose tolerance data from the National Health and Nutrition Examination Survey (NHANES) II and Hispanic Health and Nutrition Examination Survey (HHANES).

RESULTS

Prevalence of undiagnosed NIDDM based on the NHANES II and HHANES increased with age, obesity, and family history of diabetes, reaching 11.7% in people with all three risk factors. Based on the NHIS, 77.5% of U.S. adults with no medical history of diabetes (131 million people) had at least one risk factor for NIDDM or complication related to NIDDM, and 22.9% (38 million people) had three or more risk factors or complications. Approximately 31% of adults reported being screened for diabetes in the past year. Screening rates increased with an increasing number of risk factors, but even among those with three risk factors, only 38.6% were screened for NIDDM.

CONCLUSIONS

More than 7 million U.S. adults have undiagnosed NIDDM. Nevertheless, screening for diabetes in high-risk groups occurs substantially less frequently than necessary to detect undiagnosed NIDDM and institute appropriate hypoglycemic treatment.

Serum lipoproteins in African Americans and whites with non-insulin-dependent diabetes in the US population

BACKGROUND

Despite the significant role that dyslipidemia is believed to play in the development of cardiovascular disease in diabetes, most studies examining diabetic dyslipidemia in the United States have not been population based, and very little data are available for African Americans with diabetes. We used data from a national survey to compare the effect of diabetes on lipid concentrations in African-American and white men and women. In addition, we examined other factors related to lipid concentrations and controlled for these factors in our analyses.

METHODS AND RESULTS

The Second National Health and Nutrition Examination Survey included a representative sample of 4177 African Americans and whites in the US civilian noninstitutionalized population 20 to 74 years old. These persons were classified as having non-insulin-dependent diabetes mellitus (NIDDM) (n = 720) or as being nondiabetic (n = 3457) based on an oral glucose tolerance test and a medical history of diabetes. Subjects were given an interview and physical examination that included measurement of serum lipoproteins, body mass index, body fat distribution, dietary fat intake, alcohol consumption, frequency of smoking, and use of medications. By univariate analysis, a worse profile of mean cholesterol, triglycerides, and high-density lipoprotein cholesterol levels was generally apparent in NIDDM than in nondiabetic subjects, regardless of race or sex; a similar pattern was found for the prevalence of abnormal concentrations of these lipids. Lipid profiles appeared to be worse in whites with NIDDM than in African Americans. For mean total and low-density lipoprotein cholesterol, concentrations tended to be worse in women with NIDDM than in men. When other factors significantly affecting lipid levels were adjusted by multivariate analysis, we found that in all race/sex groups, total cholesterol was higher in NIDDM than in nondiabetic subjects but differences were not significant (P = 54), triglyceride concentrations were significantly higher in NIDDM subjects (P < .0001), and high-density lipoprotein cholesterol concentrations were lower in NIDDM subjects (P = .003). An interaction of diabetes with race was found for low-density lipoprotein cholesterol (P = .0001), where concentrations were substantially lower in NIDDM than in nondiabetic subjects among African Americans (P < .01) but slightly higher in NIDDM subjects among whites (P = .33). For other lipids, no differential effect of NIDDM was found by race or sex.

CONCLUSIONS

In African-American and white men and women in the United States, NIDDM is associated with a pattern of dyslipidemia that may potentiate the atherosclerotic process. Diabetic treatment should include aggressive treatment of dyslipidemia to reduce this increased risk.

Frequency and determinants of diabetes patient education among adults in the U.S. population

OBJECTIVE

To determine the proportion of adults with diabetes in the U.S. who have received diabetes patient education and to assess factors that determine whether patients receive this education.

RESEARCH DESIGN AND METHODS

A questionnaire on diabetes was administered to a representative sample of 2,405 diabetic individuals > or = 18 years of age in the U.S. population. The questionnaire inquired about whether these individuals had ever attended a diabetes education class or program. Sociodemographic and clinical factors that may influence participation in patient education were also determined.

RESULTS

Of all people with diabetes, 35.1% had attended a class or program about diabetes at some time during the course of their disease, including 58.6% of individuals with insulin-dependent diabetes mellitus, 48.9% of insulin-treated individuals with non-insulin-dependent diabetes mellitus (NIDDM), and 23.7% of NIDDM individuals not treated with insulin. Younger age, black race, residence in the midwest region of the U.S., higher level of education, and presence of diabetes complications were consistently associated with having had diabetes education for people with NIDDM. Although increasing income was associated with patient education for NIDDM individuals not treated with insulin, it was not an independent determinant for insulin-treated NIDDM individuals. NIDDM individuals not treated with insulin who lived alone were more likely to have had patient education than those who did not live alone. Not having a diabetes physician or not visiting one in the past year was associated with a higher likelihood of patient education for non-insulin-treated NIDDM individuals.

CONCLUSIONS

A large proportion of patients with diabetes has never received diabetes education. Patient education has been recognized for its contributions to reducing the morbidity and mortality of diabetes. Consequently, special attention should be directed to the subgroups of individuals, such as those not taking insulin, those with lower socioeconomic status, and those living outside urban areas, in which the frequency of diabetes patient education is particularly low.

The DCCT and medical care for diabetes in the U.S

The Diabetes Control and Complications Trial (DCCT) has convincingly established that intensive treatment of insulin-dependent diabetes mellitus (IDDM) can substantially reduce the incidence and progression of retinopathy, nephropathy, and neuropathy (1). Development of retinopathy in those without retinopathy at baseline was reduced by 76%, and progression of retinopathy in those with early retinal disease at baseline was reduced by 54%. Intensive therapy was associated with a 39% reduction in the occurrence of microalbuminuria (≥40 mg of urine albumin per 24 h) and a 54% reduction in the incidence of albuminuria (≥300 mg of urine albumin per 24 h). Development of clinical neuropathy was reduced by 60%. A reduction also occurred in macrovascular disease events (41%), although this did not reach statistical significance.

Differences in survival between black and white patients with diabetic end-stage renal disease

OBJECTIVE

To evaluate whether the longer survival of blacks with diabetic end-stage renal disease (ESRD) relative to whites is due to racial differences in type of diabetes, comorbidity at ESRD onset, and ESRD treatment modality and to examine whether survival differences between blacks and whites occur only in certain population subgroups.

RESEARCH DESIGN AND METHODS

The Michigan Kidney Registry was used to ascertain all blacks and whites (n = 594) with diabetic ESRD in southeastern Michigan, with ESRD onset at age < 65 years during 1974-1983. Patients were followed through 1988. Medical records were abstracted for type of diabetes, comorbidity at ESRD onset, and other factors.

RESULTS

Median survival among insulin-dependent diabetes mellitus patients was 27 months in blacks and 17 months in whites, and among non-insulin-dependent diabetes mellitus patients was 30 months in blacks and 16 months in whites. After adjustment for confounding factors by Cox proportional hazards analysis, the death rate was 45% lower in blacks than in whites on dialysis (relative death rate [RDR] = 0.55, 95% confidence interval [CI] = 0.44-0.69), but was similar in blacks and whites with a renal transplant (RDR = 0.99, 95% CI = 0.64-1.52). Compared with dialysis, transplantation was associated with lower mortality in both races (white, RDR = 0.50, 95% CI = 0.36-0.70; blacks, RDR = 0.89, 95% CI = 0.60-1.34), although the effect was not statistically significant in blacks. Racial differences in survival did not vary by type of diabetes or any additional factor.

CONCLUSIONS

Survival after ESRD onset is longer in blacks than in whites treated with dialysis, even after adjusting for comorbidity and other factors that affect survival. Survival does not differ by race among transplant patients.

Health-insurance coverage for adults with diabetes in the U.S. population

OBJECTIVE

To compare the extent and types of health insurance coverage for adults with diabetes to coverage for those without diabetes in the U.S. population.

RESEARCH DESIGN AND METHODS

Nationally representative samples of 2,405 adults with diabetes and 20,131 adults who were not known to have diabetes in the U.S. completed a questionnaire on current health insurance, including coverage through Medicare, private insurance, the military, and Medicaid and other public programs.

RESULTS

Among all adults with diabetes, 92.0% have some form of health insurance, including 86.5% of those 18-64 years of age and 98.8% of those > or = 65 years of age. Approximately 41% are covered by more than one health insurance mechanism, but almost 600,000 people with diabetes do not have any form of health-care coverage. Little difference was found by type of diabetes in the proportion who have health insurance. Only small differences exist between people with diabetes and those without diabetes in the percentages covered and the types of health-care coverage. Government-funded programs are responsible for health-care coverage of 57.4% of adults with diabetes, including 26.4% of those 18-64 years of age and 96.0% of those > or = 65 years of age. Private health insurance is held by 69.3% of diabetic people. Lack of private insurance appears to be attributable primarily to lower income.

CONCLUSIONS

Almost all patients with diabetes who are > or = 65 years of age have health-care coverage, but 13.5% of those 18-64 years of age have no health insurance. Few differences exist in coverage between individuals with and without diabetes. However, the absence of insurance should have a substantially greater impact on the ability of patients with diabetes to obtain services necessary for care of their disease, compared with those without diabetes. Government-funded insurance mechanisms cover a large proportion of diabetic patients, which indicates a significant societal burden associated with diabetes. Any changes in government reimbursement and coverage policies could have a major impact on health care for patients with diabetes.

Fasting plasma glucose in screening for NIDDM in the U.S. and Israel

OBJECTIVE--To demonstrate the inadequacy of fasting plasma glucose for screening for NIDDM, even among groups at high risk for diabetes. RESEARCH DESIGN AND METHODS--Representative samples of adults 40-69 years of age in the U.S. (n = 2,035) and Israel (n = 2,316) were selected. Fasting plasma glucose (FPG) was measured and a 2-h oral glucose tolerance test (OGTT) was administered. Subjects with undiagnosed NIDDM were identified using internationally accepted diagnostic criteria (FPG > or = 7.8 mM or 2-h plasma glucose > or = 11.1 mM). RESULTS--Only 31-38% of subjects with undiagnosed NIDDM had fasting hyperglycemia (> or = 7.8 mM), and 36% in the U.S. and 19% in Israel had normoglycemia (< 6.1 mM). Postchallenge glucose, diagnostic of diabetes, was associated with all fasting values, including values < 5.0 mM. Based on sensitivity, specificity, and positive predictive value, no FPG level provided a satisfactory cutoff point to use in screening for undiagnosed NIDDM. Sensitivity at each FPG cutoff point varied little among groups classified by age, sex, race, blood pressure status, or body mass index (BMI) levels > 23, but sensitivity was lower among those with BMI levels < 23. CONCLUSIONS--In the clinical setting, FPG is commonly used in screening for NIDDM. However, fasting values < or = 7.8 mM are highly insensitive for detecting NIDDM. Lower FPG cutoff points tha achieve acceptable sensitivity are accompanied by inadequately low specificity, require a high percentage of patients to be retested, and result in a low yield of diabetes among those screened. Clinicians and researchers who seek detection of undiagnosed NIDDM should use the OGTT, because FPG lacks adequate sensitivity and specificity for this purpose.

Screening for NIDDM. Why is there no national program

Non-insulin-dependent diabetes mellitus (NIDDM) is a major clinical and public health problem in the U. S. The prevalence of NIDDM is 7% among all adults and reaches over 20% among those 65–74 years of age (1–3). NIDDM and insulin-dependent diabetes mellitus (1DDM) combined account for 50% of all nontraumatic amputations in the U. S., 15% of all blindness, and 35% of all end-stage renal disease (4). At least 50% of these events occur in NIDDM patients (5–7). Prevalence of neuropathy and ischemic heart disease in NIDDM and risk of death from cardiovascular disease is two to three times that of those without diabetes even after adjusting for other risk factors (8–13).

Ophthalmic examination among adults with diagnosed diabetes mellitus

OBJECTIVE

To assess whether adults with diagnosed diabetes in the United States are receiving recommended eye examinations for detection of diabetic retinopathy and what factors are associated with receiving them.

DESIGN, SETTING, AND PARTICIPANTS

The design was a cross-sectional survey of the civilian, noninstitutionalized US population 18 years of age or older, based on the 1989 National Health Interview Survey. A multistage probability sampling strategy was used to identify a representative sample of 84,572 persons. A questionnaire on diabetes was administered to all subjects with diagnosed diabetes (n = 2405).

MAIN OUTCOME MEASURE

A dilated eye examination in the past year.

MAIN RESULTS

Of all adults with diagnosed diabetes in the United States, only 49% had a dilated eye examination in the past year. This included 57% of people with insulin-dependent diabetes mellitus (IDDM), 55% with insulin-treated non-insulin-dependent diabetes mellitus (NIDDM), and 44% with NIDDM not treated with insulin. Even among diabetics at high risk of vision loss because of retinopathy or long duration of diabetes, the proportion with a dilated eye examination was only 61% and 57%, respectively. By logistic regression, the probability of a dilated eye examination among persons with NIDDM increased with older age, higher socioeconomic status, and having attended a diabetes education class. The probability of a dilated eye examination was not independently related to race, duration of diabetes, frequency of physician visits for diabetes, or health insurance.

CONCLUSIONS

About half of adults with diabetes in the United States are not receiving timely and recommended eye care to detect and treat retinopathy. Widespread interventions, including patient and professional education, are needed to ensure that diabetic patients who are not receiving appropriate eye care have an annual dilated eye examination to detect retinopathy and prevent vision loss.

Self-monitoring of blood glucose by adults with diabetes in the United States population

OBJECTIVE

To evaluate self-monitoring of blood glucose, which is considered an important practice for patients with diabetes. However, little is known about the frequency or determinants of this technique.

RESEARCH DESIGN AND METHODS

A detailed questionnaire on diabetes was administered to a representative sample of 2405 diabetic subjects > or = 18 yr of age in the U.S. population in the 1989 National Health Interview Survey.

RESULTS

Among subjects with IDDM, 40% monitored their blood glucose at least 1 time/day. Among subjects with NIDDM treated with insulin, 26% monitored at least 1 time/day and among NIDDM subjects not treated with insulin, the percentage was 5%. When stratified by age, little difference was observed between IDDM subjects and insulin-treated NIDDM subjects in the percentage testing at least 1 time/day. By multivariate analysis, age and insulin use were the major determinants of whether diabetic subjects tested their blood glucose. Race and education were also independently related to self-monitoring of blood glucose. Blacks were 60% less likely to test their blood glucose at least 1 time/day compared with non-Hispanic whites and Mexican Americans. Those with college education were 80% more likely to test their blood glucose compared with those with lower education levels. Having had a patient education class in diabetes management and frequent physician visits for diabetes care were positively related to self-testing. Self-monitoring was not related to higher income or having health insurance.

CONCLUSIONS

A large proportion of patients with diabetes do not test their blood glucose. Financial barriers associated with income and health insurance do not appear to impede the practice of self-monitoring. Because of the importance of blood glucose control in the prevention of diabetes complications and the role of self-monitoring in achieving blood glucose control, it may be prudent for physicians and their patients to make greater use of this technique. Special attention should be directed to the subgroups of patients (blacks, patients not treated with insulin, those with less education, and those with no education in diabetes) in which the frequency of self-monitoring is particularly low.

Attitudes and behaviors of primary care physicians regarding tight control of blood glucose in IDDM patients

OBJECTIVE--To evaluate attitudes and practices of primary-care physicians toward tight blood glucose control in IDDM. RESEARCH DESIGN AND METHODS--A mail and telephone questionnaire survey was conducted on a systematic, stratified sample of 1429 family-practice physicians, general practitioners, internists, and pediatricians in active practice in the United States who treated patients with IDDM. Physicians were asked about methods they used for clinical and laboratory assessment of blood glucose control and about their attitudes and beliefs in treating IDDM. They were asked also what they consider to be acceptable ranges for blood glucose and HbA1 in IDDM patients. A score was developed reflecting three criteria for tight blood glucose control: fasting glucose 70-120 mg/dl (3.9-6.7 mM), 2-h postprandial glucose < 180 mg/dl (< 10 mM), and HbA1 < or = 8% (the nondiabetic value was specified as 5-7%). Physicians were accorded one point when their acceptable range agreed with an intensive treatment criterion (range for score 0-3). RESULTS--Only 31% of physicians agreed with all three criteria for tight control of blood glucose; 37% agreed with none or only one of the standards. Pediatricians were particularly low in their agreement with the HbA1 standard. Physicians who agreed with one of the three criteria often did not agree with the other two. With increasing value for the score, there was a greater proportion of physicians whose management practices (e.g., frequent measurement of HbA1, multiple insulin injections, patient SMBG, use of dietitian/educator in care of patients) are conducive toward tight control of blood glucose. However, even among physicians with a score of 3, HbA1 was ordered infrequently, three or more insulin injections/day was prescribed rarely, patient SMBG was less than fully endorsed, and both a dietitian and diabetes educator were used by a minority of physicians. CONCLUSIONS--It appears that primary-care physicians are not fully aware of recommended criteria for intensive treatment of blood glucose in IDDM patients or of the importance of multiple insulin injections, use of HbA1, and patient SMBG. Physician practice behaviors are less than optimal for intensive management of IDDM patients, even among physicians who agree with all three standards for intensive treatment of blood glucose in IDDM.

Effect of multiple risk factors on differences between blacks and whites in the prevalence of non-insulin-dependent diabetes mellitus in the United States

The higher prevalence of non-insulin-dependent diabetes mellitus (NIDDM) in US blacks as compared with whites may be due to a higher frequency of NIDDM risk factors in blacks, a higher inherent susceptibility to NIDDM among blacks, or the risk factors' having a greater effect in blacks. The authors evaluated 4,379 subjects from the Second National Health and Nutrition Examination Survey (1976-1980) for whom NIDDM was ascertained by medical history and oral glucose tolerance test, and for whom data on a number of risk factors were available. The prevalence of NIDDM was 60% higher in blacks than in whites (p < 0.001) and was highest in black women. Although most risk factors for NIDDM were more common in blacks, this higher frequency did not completely explain the racial disparity in the prevalence of NIDDM. After adjustment for all risk factors by logistic regression, an elevated risk of NIDDM was particularly evident at higher obesity levels in blacks as compared with whites; the odds were 70% higher for blacks at a percentage of desirable weight of 150 (95% confidence interval 1.1-2.8). The risk of NIDDM associated with obesity was greatest in black women: The odds in this group were sevenfold higher at a percentage of desirable weight of 150 versus 100 (95% confidence interval 2.6-18.8). The possibility of racial differences in metabolic adaptation to obesity highlights the importance of preventing this condition in blacks, particularly in black women.

Onset of NIDDM occurs at least 4-7 yr before clinical diagnosis

OBJECTIVE

To investigate duration of the period between diabetes onset and its clinical diagnosis.

RESEARCH DESIGN AND METHODS

Two population-based groups of white patients with non-insulin-dependent diabetes (NIDDM) in the United States and Australia were studied. Prevalence of retinopathy and duration of diabetes subsequent to clinical diagnosis were determined for all subjects. Weighted linear regression was used to examine the relationship between diabetes duration and prevalence of retinopathy.

RESULTS

Prevalence of retinopathy at clinical diagnosis of diabetes was estimated to be 20.8% in the U.S. and 9.9% in Australia and increased linearly with longer duration of diabetes. By extrapolating this linear relationship to the time when retinopathy prevalence was estimated to be zero, onset of detectable retinopathy was calculated to have occurred approximately 4-7 yr before diagnosis of NIDDM. Because other data indicate that diabetes may be present for 5 yr before retinopathy becomes evident, onset of NIDDM may occur 9-12 yr before its clinical diagnosis.

CONCLUSIONS

These findings suggest that undiagnosed NIDDM is not a benign condition. Clinically significant morbidity is present at diagnosis and for years before diagnosis. During this preclinical period, treatment is not being offered for diabetes or its specific complications, despite the fact that reduction in hyperglycemia, hypertension, and cardiovascular risk factors is believed to benefit patients. Imprecise dating of diabetes onset also obscures investigations of the etiology of NIDDM and studies of the nature and importance of risk factors for diabetes complications.

Prevalence of diabetes in Mexican Americans, Cubans, and Puerto Ricans from the Hispanic Health and Nutrition Examination Survey, 1982-1984

The purpose of this study was to estimate the prevalence of diagnosed and undiagnosed diabetes among Mexican Americans, Cubans, and Puerto Ricans in the United States and compare these estimates to data from prior surveys for U.S. non-Hispanic whites and blacks. Data for this study are from the Hispanic Health and Nutrition Examination Survey, a multipurpose cross-sectional survey of three U.S. Hispanic populations conducted in 1982-1984. The interviewed sample of people aged 20-74 yr included 3935 Mexican Americans in the southwest, 1134 Cubans in Florida, and 1519 Puerto Ricans in the New York City area. The diabetes component consisted of interview questions on diabetes diagnosis and treatment and an oral glucose tolerance test administered to a subsample. The prevalence of diabetes was two to three times greater for Mexican Americans and Puerto Ricans than for non-Hispanic whites surveyed in 1976-1980. In Cubans, the prevalence was similar to that for non-Hispanic whites. In men and women 45-74 yr of age, the prevalence of diabetes was extremely high for both Mexican Americans (23.9%) and Puerto Ricans (26.1%) compared with Cubans (15.8%) or non-Hispanic whites (12%). The total prevalence of diabetes was not significantly different for Mexican Americans and Puerto Ricans but was significantly lower for Cubans. The relatively lower prevalence of diabetes among Cubans and the high prevalence in both Mexican Americans and Puerto Ricans may be related to socioeconomic, genetic, behavioral, or environmental factors.

Epidemiological correlates of NIDDM in Hispanics, whites, and blacks in the U.S. population

Characteristics, prevalence, and risk factors for non-insulin-dependent diabetes mellitus (NIDDM) among Hispanics, blacks, and whites aged 20-74 yr in the United States population were investigated with two national surveys that used a household interview to ascertain diagnosed diabetes and a 75-g 2-h oral glucose tolerance test to measure undiagnosed diabetes. The Hispanic Health and Nutrition Examination Survey of 1982-1984 studied Mexican Americans in the southwest U.S., Cuban Americans in the Miami, Florida, area, and Puerto Ricans in the New York City area. The National Health and Nutrition Examination Survey of 1976-1980 examined a national sample of U.S. residents, of whom data on blacks and whites were analyzed. People with diagnosed diabetes in the five populations were similar with respect to mean age (53-57 yr), age at diagnosis (45-48 yr), duration of diabetes (6.9-8.7 yr), and diabetes therapies (58-67% using pharmacological treatment). Mean age of people with undiagnosed diabetes (51-59 yr) was comparable to that of diagnosed cases, and mean fasting (7.1-7.8 mM) and 2-h postchallenge plasma glucose (14.1-15.5 mM) values for people with undiagnosed diabetes were similar among the five populations. However, obesity levels varied by race, sex, and whether diabetes was diagnosed or undiagnosed. Age-standardized prevalence of diabetes (sum of diagnosed and undiagnosed cases) was 6.2% in whites, 9.3% in Cubans, 10.2% in blacks, 13% in Mexican Americans, and 13.4% in Puerto Ricans. Thus, compared to whites, diabetes rates were 50-60% higher among Cubans and blacks and 110-120% higher among Mexican Americans and Puerto Ricans. Age-standardized rates of impaired glucose tolerance were similar among the five populations (10.3-13.8%). Increasing age, obesity, and family history of diabetes were associated with higher rates of diabetes but sex, physical activity, education, income, and acculturation were not risk factors or were only weakly associated with diabetes prevalence.