Parental hypertension and proteinuria in Pima Indians with NIDDM

To determine if parental hypertension is associated with proteinuria in offspring with non-insulin-dependent diabetes mellitus (NIDDM), 438 diabetic Pima Indians (172 men, 266 women) aged 20 years or more and both of their parents were examined. Hypertension was defined as a systolic blood pressure 140 mm Hg or more, diastolic blood pressure 90 mm Hg or more, or treatment with antihypertensive medicine. Sixty-three percent of the fathers and 80% of the mothers had diabetes at the time their blood pressure was measured. Families in which either parent had proteinuria, defined as a urine protein-to-creatinine ratio > or = 0.5 g/g were excluded; 73 (16.7%) of the offspring had proteinuria. The prevalence rates of proteinuria in the offspring were similar if neither parent or only one parent had hypertension (8.9 and 9.4%, respectively), but was significantly higher if both parents had hypertension (18.8%), after adjustment for age, sex, duration of diabetes, and 2-h post-load plasma glucose concentration in the offspring and diabetes in the parents by logistic regression. The odds for proteinuria being present in the offspring if both parents had hypertension was 2.2 times (95% confidence interval, 1.2 to 4.2) that if only one parent had hypertension. When mean arterial pressure and blood pressure treatment in the offspring were added to the model the relationship remained (odds ratio = 2.2; 95% confidence interval, 1.1 to 4.3). Hypertension in both parents is associated with the development of proteinuria in offspring with NIDDM. This relationship was present even when controlled for the effects of blood pressure and its treatment in the offspring.

HLA*A2 confers mortality risk for cardiovascular disease in Pimans

A sample of 1465 full heritage Piman Indians from Arizona were typed for the serological antigens of the HLA class I loci and then incorporated into a survival study that ended December 31, 1991. The total follow-up time was 11,749 person-years with an average of 8.0 years per person. During the study 298 persons died, 54 from cardiovascular disease (CVD). Allele HLA*A2 conferred a 4.94 fold rate for death from CVD (95% C.I. 1.91-12.77). When controlled for the potential confounding variables, cholesterol, mean blood pressure, smoking, body mass index, rheumatoid factor titer, and nephropathy, the mortality rate ratio (MRR) was 5.42 (95% C.I. 1.98-14.82). There was no statistically significant association of mortality with other HLA-A or HLA-B alleles, or for causes of death not related to cardiovascular disease.

Hypertension in Pima Indians: prevalence and predictors

THE PIMA INDIANS HAVE THE WORLD'S HIGHEST reported incidence of diabetes. Since 1965, this population has participated in a longitudinal epidemiological study of diabetes and its complications. The examinations have included a medical history for diabetes and other major health problems. The focus of this study is the correlation between the prevalence of hypertension and glucose tolerance in this population. Of the 4315 adults ages 18 and older, 50% had normal glucose tolerance; 12%, impaired glucose tolerance (IGT); 8%, newly diagnosed diabetes; and 31%, previously diagnosed diabetes of a mean duration of 11 years. Age-sex adjusted prevalence of hypertension was 24% in those with normal glucose tolerance, 34% in those with IGT, and 40% in those with diabetes. Hypertension was more common in men than in women and was positively related to obesity. Of the 2667 children ages 6 to 17 years, 4% had IGT, and 1% had diabetes. Blood pressure was higher in boys than girls and was associated with older age and worse glucose tolerance. Longitudinal analyses of data from 188 children ages 5 to 9 years who had their follow-up exam at ages 18 to 24 revealed no relationship between insulin concentration and blood pressure in either sex. In this group mean blood pressure at followup was positively correlated with relative weight, mean blood pressure, and 2-hour post-load plasma glucose concentration at baseline. In a multiple regression model, relative weight was the strongest predictor of mean blood pressure at the follow-up exam.

Prediabetic blood pressure and familial predisposition to renal disease in Pima Indians with non-insulin-dependent diabetes mellitus

Renal disease is a frequent complication of non-insulin-dependent diabetes in the Pima Indians from the Gila River Indian Community in Arizona. This review describes the relationship between prediabetic blood pressure and the subsequent development of renal disease, and characterizes the familial aggregation of diabetic renal disease in this population.

The U-shaped association between body mass index and mortality: relationship with weight gain in a Native American population

In order to determine whether weight loss explains high mortality rates in those with a low body mass index (BMI), the relationships between BMI, rate of weight gain and mortality were examined in Pima Indians. Subjects were 814 diabetic and 1814 nondiabetic participants in a longitudinal survey who had at least two examinations after age 20. Median duration of follow-up was 8.1 (range 0.03-25.1) years. BMI showed a U-shaped relationship with mortality rates in men with the lowest rates in the 30-35 kg/m2 category; an inverse relationship was seen in women. Subjects who were losing weight had higher mortality rates than those who were gaining. However, excess mortality among the lightest subjects was present among those who were gaining weight. Among nondiabetic subjects, the mortality ratio (MR) for BMI < 25 kg/m2 compared with 30-35 kg/m2 was 1.5 [95% confidence interval (CI) 1.0-2.2] unadjusted for weight gain, while the adjusted MR was 1.3 [95% CI 0.9-1.9]. Weight loss, which may reflect underlying illness, is associated with high mortality rates in Pima Indians but does not fully account for the high mortality in the lightest individuals.

Segregation analysis of non-insulin-dependent diabetes mellitus in Pima Indians: evidence for a major-gene effect

Non-insulin-dependent diabetes mellitus (NIDDM) has a high prevalence in Pima Indians. The disorder is familial, but the extent to which genetic factors are involved in its etiology is largely unknown. Segregation analysis was used to determine whether familial aggregation of NIDDM in this population could reflect the action of a single major gene. The analysis included 2,697 subjects from 653 nuclear families in which both parents and at least one offspring had been examined in the course of a longitudinal epidemiological study. The REGTL program of the SAGE package was used to fit models in which age at onset of NIDDM is transmitted from parent to offspring under the unified model for segregation analysis. Likelihood-ratio tests were used to test hypotheses related to genetic transmission. The hypothesis of no major effect was strongly rejected (P < .01), as was that of no transmission of the major effect (P < .01). Mendelian transmission was not rejected (P = .91). Similar results were obtained when covariates for obesity and birth cohort were added to the models and when a power transformation of age at onset was estimated. A strong effect of birth cohort with earlier age at onset in the later born cohorts was observed (P < .01). The findings are consistent with the hypothesis that a major gene influences the risk for NIDDM in Pima Indians by affecting age at onset. The expression of this gene may depend on environmental factors that have become more prevalent in recent-birth cohorts.

Preventing non-insulin-dependent diabetes

Many risk factors for non-insulin-dependent diabetes mellitus (NIDDM), such as obesity, physical inactivity, and high-fat diet, can potentially be modified. Furthermore, some of the metabolic abnormalities, such as insulin resistance and impaired glucose tolerance, that predict diabetes can be improved by behavior modification and drug treatment. Thus, at least to some extent, NIDDM may be preventable. Several small clinical trials have addressed the hypothesis that NIDDM can be prevented by dietary modification, physical activity, or drug treatment. Some studies suggest a preventive effect, but the conclusions are limited by considerations of sample size, randomization, or intensity of the interventions. Consequently, the hypothesis that NIDDM is preventable requires further testing.

Familial relationships between obesity and NIDDM

Obesity and family history of diabetes are both risk factors for non-insulin-dependent diabetes mellitus (NIDDM), but it has been proposed that lean individuals with NIDDM have a greater load of diabetes susceptibility genes. If this is the case, one might expect a high prevalence of NIDDM in relatives of diabetic individuals with a low body mass index (BMI). Among Pima Indians participating in an epidemiological study, prevalence of NIDDM was evaluated in relation to BMI of a diabetic parent or to the average parental BMI when both parents had diabetes in 1,535 offspring from 547 families. Prevalence of NIDDM was also evaluated in relation to BMI of a randomly selected index diabetic sibling in 1,722 siblings from 721 families. NIDDM was diagnosed by an oral glucose tolerance test. Compared with offspring of diabetic parent(s) at the 25th percentile of BMI, the odds ratio (OR) for diabetes in offspring of diabetic parents at the 75th percentile was 0.6 (95% confidence interval [CI] 0.5-0.7), adjusted for age, sex, BMI in offspring, number of diabetic parents, and age at onset of diabetes and sex of the diabetic parent(s). In the analysis according to BMI in a diabetic sibling, the corresponding OR was 0.8 (95% CI 0.6-0.9). Risk ratios were only modestly higher when the analysis was restricted to relatives of subjects whose BMI had been determined before the onset of diabetes. NIDDM in the presence of a low BMI is more strongly familial than that at a higher BMI.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison of body size measurements as predictors of NIDDM in Pima Indians

OBJECTIVE--To determine and compare the abilities of various anthropometric measurements to predict the development of non-insulin-dependent diabetes mellitus (NIDDM) in Pima Indian men and women. RESEARCH DESIGN AND METHODS--A total of 290 male and 443 female Pima Indians were followed for up to 6 years for the development of NIDDM. A proportional hazards analysis was used to assess the ability of anthropometric measurements evaluated at baseline to predict NIDDM. Receiver operating characteristic (ROC) curves were used to compare individual variables in predicting NIDDM. RESULTS--In separate models controlled for age and sex, body mass index (BMI), waist circumference, thigh circumference, waist-to-thigh ratio (WTR), weight, and percentage body fat (PBF) estimated by bioelectric resistance each predicted NIDDM, which developed in 30 men and 52 women. The highest incidence rate ratios (IRRs; for 1 SD of a variable) were for WTR in men and for PBF in women, although the confidence interval (CI) for PBF was wide. In stepwise analyses, WTR was the most significant predictor in men (IRR for 1 SD = 1.58, 95% CI = 1.20-2.07), and BMI was the most significant predictor in women (IRR for 1 SD = 1.65, 95% CI = 1.29-2.11). However, by ROC analyses, thigh circumference was the only variable significantly worse than WTR in men or BMI in women at predicting NIDDM. CONCLUSIONS-- Measurements such as waist circumference, WTR, weight, and BMI may be useful as more complicated measurements, such as PBF by bioelectrical resistance, for identifying groups of individuals whose body habitus places them at high risk of developing NIDDM.

Screening for mtDNA diabetes mutations in Pima Indians with NIDDM

More than half of the Pima Indians over age 35 years have non-insulin-dependent (type II) diabetes mellitus (NIDDM). Extensive data indicate the importance of maternal diabetes in determining their risk for diabetes. Generally, the risk of having NIDDM is higher in patients with affected mothers than affected fathers. This has been attributed to intrauterine factors, but recently mitochondrial inheritance has been raised as an alternative hypothesis. In other populations, several families and individuals with diabetes due to a mitochondrial DNA point mutation at nucleotide 3243 in the tRNA(leu(UUR)) gene have been described, as has one family with a 10.4 kb mitochondrial DNA duplication/deletion. We tested whether these specific mitochondrial gene mutations could explain a portion of the excess maternal transmission seen in the Pima Indians. Mitochondrial DNA obtained from blood lymphocytes of 148 Pima Indians with NIDDM was screened both for the point mutation at nt 3243, and the 10.4 kb duplication/deletion. Neither of these mutations was detected, and although a small proportion of the excess maternal transmission in Pima Indians could still be due to yet undescribed mitochondrial mutations or imprinted nuclear genes, our data support the role of the intrauterine environment in this population.

Rate of weight gain, weight fluctuation, and incidence of NIDDM

The relationships of rate of weight gain and weight fluctuation to incidence of non-insulin-dependent diabetes mellitus (NIDDM) were examined in Pima Indians. The 1,458 subjects were participants in a prospective study with examinations approximately every 2 years. Rate of weight gain was defined as the slope of the regression line of weight with time for two or more consecutive examinations > or = 2 years apart and weight fluctuation as the root-mean-square departure from this line for four examinations. Among men, incidence of NIDDM was strongly and significantly related to rate of weight gain (e.g., age-adjusted incidence = 56.7/1,000 person-years in those with weight gain > or = 3 kg/year and 16.9/1,000 person-years for those losing weight [Ptrend < 0.01]). In women, weight gain was significantly related to diabetes incidence only in those who were not initially overweight (body mass index < 27.3 kg/m2). In contrast to the relationship with weight gain, weight fluctuation was not associated with incidence of diabetes in either sex. These findings suggest that weight control in overweight individuals may be a more effective strategy for prevention of NIDDM in men than in women, whereas prevention of obesity may prevent diabetes in both sexes. Concern about a diabetogenic effect of weight fluctuation should not deter weight-control efforts.

Diabetic nephropathy: a risk factor for diabetes mellitus in offspring

Both non-insulin-dependent diabetes mellitus and diabetic nephropathy show familial aggregation. If diabetes and renal disease have independent determinants (genetic or otherwise), offspring of parents with diabetic renal disease should have a similar risk of diabetes to those offspring of parents with diabetes alone. To test this hypothesis, the prevalence of diabetes was examined in a population-based pedigree study in Pima Indian offspring of three mutually exclusive parental types: 1) diabetic with renal disease, 2) diabetic, but without renal disease and 3) non-diabetic. Among offspring of one diabetic parent and one non-diabetic parent (n = 320) the prevalence of diabetes at ages 15-24 years and 25-34 years was 0% and 11%, respectively if the diabetic parent did not have renal disease compared with 6% and 28% respectively if the diabetic parent did have renal disease. Corresponding rates for offspring of two diabetic parents (n = 121) were 10% and 17%, respectively if neither parent had renal disease compared with 30% and 50%, respectively if one parent did have renal disease. The presence of renal disease in a parent with diabetes relative to diabetes alone was associated with 2.5 times the odds of diabetes (95% confidence interval 1.4-4.3) in the offspring controlled for age, age at onset of parental diabetes and diabetes in the other parent using logistic regression. These findings provide support for parental diabetic renal disease, independent of age at onset of parental diabetes, conferring an increased risk for diabetes in the offspring.(ABSTRACT TRUNCATED AT 250 WORDS)

Incidence and determinants of elevated urinary albumin excretion in Pima Indians with NIDDM

OBJECTIVE

To examine the incidence and determinants of elevated urinary albumin excretion in Pima Indians with non-insulin-dependent diabetes mellitus (NIDDM).

RESEARCH DESIGN AND METHODS

The incidence of elevated urinary albumin excretion (> or = 30 mg albumin/g creatinine) and its relationship with baseline characteristics was determined in 456 Pima Indians > or = 15 years old with NIDDM who were followed for up to 11.6 years (median 4.7 years).

RESULTS

Of these 456 subjects, 192 (42%; 58 men, 134 women) developed elevated urinary albumin excretion, 172 of whom (90%) were within the microalbuminuric range (30-299 mg/g). The incidence of elevated urinary albumin excretion was related to retinopathy, type, of diabetes treatment, longer duration of diabetes, lower body mass index, and higher values of mean arterial pressure, HbA1, and fasting and 2-h postload plasma glucose concentration at the baseline examination, but not to sex. A relationship with cholesterol was found in durations of diabetes of > or = 10 years. The cumulative incidence of elevated albumin excretion was 17% after 5 years of NIDDM.

CONCLUSIONS

The incidence of elevated urinary albumin excretion in Pima Indians with NIDDM is at least as high as that reported previously in insulin-dependent diabetes mellitus, and its major determinants are the same as those shown previously to predict the development of more advanced renal disease in this population.

Early and late insulin response as predictors of NIDDM in Pima Indians with impaired glucose tolerance

Risk factors predicting deterioration to diabetes mellitus were examined in 181 subjects with impaired glucose tolerance. Fifty-seven subjects had impaired glucose tolerance on one occasion followed by normal glucose tolerance at a repeat oral glucose tolerance test, and 124 subjects had impaired glucose tolerance on two successive oral glucose tolerance tests. Subjects were followed for a median period of 5.0 years (range 1.0-17.2). The age- and sex-adjusted cumulative incidence of diabetes at 10 years of follow-up was higher in subjects who had impaired glucose tolerance on both tests (70%) than in those whose glucose tolerance was normal at the repeat test (53%), [rate ratio (RR) = 1.6, 95% confidence intervals (CI) = 1.0-2.5]. Proportional hazards analyses were used to identify baseline risk factors (measured at the repeat oral glucose tolerance test) for subsequent diabetes, and incidence rate ratios were calculated for the 90th percentile compared with the 10th percentile of each continuous variable for the whole group. In all subjects, in separate models, higher body mass index [RR = 2.0, 95% CI = 2.2-9.9], high fasting serum insulin concentrations [RR = 2.4, 95% CI = 1.4-4.2], and low early insulin response [RR = 0.5, 95% CI = 0.3-0.8] 30 min after a glucose load were significant predictors for deterioration to diabetes. In a multivariate analysis which controlled for age and sex, 120-min post-load glucose, fasting insulin and late insulin response predicted diabetes.(ABSTRACT TRUNCATED AT 250 WORDS)

Meta-analysis reveals association between most common class II haplotype in full-heritage Native Americans and rheumatoid arthritis

The association of RA with the alleles at the HLA system was tested among Pima and Tohono O'odham Indians (Pimans) of the Gila River Indian Community of Arizona. Serologic class I (HLA-A, -B, and -C) alleles were typed in 51 individuals with RA and in 302 without RA. Serologic class II (HLA-DR, DQ; DR52 DR53) alleles were typed in a subset of 47 with RA and 147 without RA. Molecular subtypes of DR3X6, DRB1*1402, and *1406 were determined in 29 individuals, 16 with RA and 13 without RA. Among the cases with RA, 46 of 47 had the serologic antigen HLA-DR3X6, as did 140 of 147 of those without the disease. However, this association was not statistically significant because of the high prevalence of the antigen in the controls. Data from Pimans were analyzed with similar results from the Tlingit and Yakima Indians. A meta-analysis employing the Mantel-Haenszel procedure, stratified by tribe, revealed a statistically significant association between the most common haplotype, DRB1*1402 DQA1*0501 DQB1*0301 DRB3*0101, and RA (summary odds ratio = 2.63, 95% confidence interval = 1.08, 6.46). There was also a statistically significant difference in the genotype distributions of one class I locus, HLA-C, between those with and without RA (chi 2 = 12.4, 5 df; p = 0.03). It is concluded that the association with the most common class II haplotype in full-heritage Native Americans might help explain their high prevalence of RA.

Comparison of World Health Organization and National Diabetes Data Group procedures to detect abnormalities of glucose tolerance during pregnancy

OBJECTIVE

To compare the one-step procedure proposed by the World Health Organization (WHO) with the two-step procedure proposed by the National Diabetes Data Group (NDDG) for the identification of abnormalities of glucose tolerance during pregnancy.

RESEARCH DESIGN AND METHODS

One hundred twenty-seven non-diabetic Pima Indian women had a 75-g 2-h glucose tolerance test (WHO criteria). Those with an elevated 1-h glucose concentration (> or = 7.8 mmol/l) were referred for a 100-g 3-h glucose tolerance test (National Diabetes Data Group criteria). The effectiveness of the two test procedures was determined by comparing the frequency of macrosomia and cesarean section as outcomes of pregnancy.

RESULTS

Of 42 women with 1-h plasma glucose concentrations > or = 7.8 mmol/l, 13 had no 100-g test, 27 had a normal test, and 2 had an abnormal test. Both women (100%) with abnormal two-step 100-g tests also had abnormal one-step 75-g tests, but only 2 of the 11 women (18%) with an abnormal one-step test had an abnormal two-step test. Sixteen of the 127 women delivered babies weighing > or = 4,000 g. Six of these women (38%) were correctly identified as abnormal using the one-step test and one (6%) using the two-step test. Of seven women delivering by cesarean section, four (57%) had abnormal one-step tests, but none had an abnormal two-step test.

CONCLUSIONS

The one-step WHO test for glucose tolerance during pregnancy was abnormal in a greater percentage of women with adverse outcomes than the more cumbersome two-step NDDG test. The one-step test has the added advantage of being directly comparable to the standard glucose tolerance test used in nonpregnant women.

A cross-sectional and longitudinal comparison of the Rome criteria for active rheumatoid arthritis (equivalent to the American College of Rheumatology 1958 criteria) and the American College of Rheumatology 1987 criteria for rheumatoid arthritis

OBJECTIVE

To compare the diagnostic properties of the Rome 1961 criteria for active rheumatoid arthritis (RA) and the American College of Rheumatology (ACR; formerly, the American Rheumatism Association) 1987 criteria for RA with regard to their ability to classify, diagnose, and predict outcome in RA.

METHODS

Analysis of cross-sectional and longitudinal data from repeated health examinations and review of clinical records of 3,509 Pima Indians followed up from January 1966 to December 1990.

RESULTS

The ACR 1987 criteria identified approximately 50% of the cases identified by the Rome 1961 criteria, in both cross-sectional and longitudinal analyses. The ACR 1987 criteria were better predictors of subsequent development of a clinically supported diagnosis and treatment with slow-acting antirheumatic drugs (both P < 0.001), but were less sensitive than the Rome 1961 criteria for detecting cases for which there already was a clinically supported diagnosis (P < 0.001).

CONCLUSION

In a population-based analysis, the ACR 1987 criteria are less sensitive for detecting clinical disease, but predict a clinically more severe prognosis, compared with the Rome 1961 criteria. The sensitivity of both sets of criteria to identify clinical disease is improved if multiple examinations or inactive disease are taken into account.

Gravidity, obesity, and non-insulin-dependent diabetes among Pima Indian women

PURPOSE

To evaluate the relationships among gravidity, obesity, and non-insulin-dependent diabetes mellitus in Pima Indian women.

SUBJECTS AND METHODS

Pima Indian women (n = 2,779) participating in a longitudinal epidemiologic study of diabetes were evaluated in both cross-sectional and longitudinal analyses.

RESULTS

The prevalence of non-insulin-dependent diabetes was higher among women who had never been pregnant than among those who had been pregnant (age- and obesity-adjusted odds ratio = 2.0; 95% confidence interval = 1.5 to 2.7). Controlled for age and obesity, nondiabetic women who had never been pregnant had significantly higher fasting plasma glucose concentrations by 2% (P = 0.004), higher fasting serum insulin concentrations by 8% (P = 0.09), and higher 2-hour serum insulin concentrations by 10% (P = 0.07) than nondiabetic women who had been pregnant. Among 1,025 women observed for an average of 8 years, those who had not been pregnant by the baseline examination were at significantly higher risk for developing non-insulin-dependent diabetes before the age of 40 years (incidence rate ratio = 1.5; 95% confidence interval = 1.2 to 2.1), but that difference could be accounted for by a higher degree of obesity.

CONCLUSIONS

We hypothesize that Pima Indian women who have a high risk for non-insulin-dependent diabetes develop obesity and hyperinsulinemia at an early age, and that may be responsible for decreased fertility because of associated changes in sex hormones.

Decreasing incidence and prevalence of rheumatoid arthritis in Pima Indians over a twenty-five-year period

OBJECTIVE

To evaluate temporal trends in the incidence of rheumatoid arthritis (RA).

METHODS

Incident cases of RA were identified among a population-based cohort of Pima Indians in Arizona over the period 1965-1990.

RESULTS

Among 2,894 subjects, 78 incident cases of RA were identified. The age-adjusted incidence declined by 55% in men (Ptrend = 0.225), and by 57% in women (Ptrend = 0.017) after controlling for oral contraceptive or estrogen use and for pregnancy experience. During the same period, age-adjusted prevalence rates of active RA decreased by 29% in men (Ptrend = 0.63) and by 40% in women (Ptrend = 0.02). Fewer than 17% of subjects with known RA were taking slow-acting antirheumatic drugs (SAARDs) in 1990.

CONCLUSION

The decrease in incidence and prevalence of RA in this population over such a short period implicates the involvement of an environmental factor(s), other than exogenous estrogens, in the pathogenesis of the disease. However, the possibility that the observed decrease might be explained by an increased use of SAARDs in subjects with RA cannot be excluded.

Familial and metabolic factors related to blood pressure in Pima Indian children

High blood pressure, abnormal glucose tolerance, and obesity are frequently associated with each other, but the mechanism of these associations is poorly understood. Studying them in children may help in understanding the pathogenesis of hypertension. Blood pressure, height, weight, and plasma glucose and serum insulin concentrations during a 75-g oral glucose tolerance test were measured in 1,698 Pima Indian children aged 6-17 years who participated in an ongoing epidemiologic study. Weight relative to height was used as an index of obesity. The parents of many of the children were also examined. Fasting and 2-hour glucose and insulin concentrations, adjusted for age, sex, and relative weight, were positively related to systolic blood pressure but not to diastolic blood pressure. Relative weight, 2-hour glucose, and fasting insulin concentrations were independently and significantly associated with systolic blood pressure in a stepwise regression analysis that included age and sex. After parental hypertension was taken into account, maternal but not paternal non-insulin-dependent diabetes mellitus, controlled for the child's relative weight and glucose and insulin concentrations, was significantly associated with higher blood pressure in children. The stronger association with maternal diabetes suggests a greater sharing of environmental factors between mother and child than between father and child, but familial similarities in obesity and glucose and insulin concentrations, the diabetic intrauterine milieu, and shared environmental factors probably all contribute to this association.

Glucose, insulin concentrations and obesity in childhood and adolescence as predictors of NIDDM

Metabolic abnormalities antedate the development of non-insulin-dependent diabetes mellitus (NIDDM) by some years. How these metabolic abnormalities relate to the genetic component of the disease and to the subsequent prediction of diabetes is unknown. The present study was designed to examine the association of parental diabetes with relative weight, fasting and 2-h plasma glucose and fasting and 2-h serum insulin in childhood, and to identify which of these variables were most predictive of subsequent NIDDM. Subjects comprised 1258 Pima Indians aged 5-19 years with normal glucose tolerance participating in a longitudinal population-based study. Age-sex-adjusted values of relative weight, fasting and 2-h glucose and fasting and 2-h insulin were positively associated with parental diabetes. Only one of 138 subjects with two non-diabetic parents developed diabetes. Among 1120 subjects with at least one diabetic parent, 101 (9.0%) developed diabetes during a mean follow up of 8.4 years. Fasting insulin was a significant predictor of diabetes, but did not add to the predictive value of relative weight. Relative weight and 2-h and fasting plasma glucose were the variables most predictive of NIDDM in childhood and adolescence. Against a background of parental diabetes, high fasting insulin concentrations predict diabetes, compatible with the hypothesis that insulin resistance is an early metabolic abnormality leading to NIDDM. In this study, however, its predictive power did not add significantly to that of relative weight, with which it was correlated.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison of tests for glycated haemoglobin and fasting and two hour plasma glucose concentrations as diagnostic methods for diabetes

OBJECTIVE

To compare the ability of tests measuring two hour plasma glucose, fasting plasma glucose, and glycated haemoglobin concentrations in predicting the specific microvascular complications of non-insulin dependent diabetes mellitus.

DESIGN

Cross sectional and longitudinal analysis of the relation between complications and concomitant results of the three tests.

SETTING

Gila River Indian Community, Arizona.

SUBJECTS

Pima Indians (cross sectional, n = 960), aged 25 years or above who were not receiving insulin or oral hypoglycaemic treatment at the baseline examination.

MAIN OUTCOME MEASURES

Development of retinopathy and nephropathy.

RESULTS

Cross sectionally, frequency distributions of logarithms of the three sets of results were bimodal, with the prevalence of retinopathy and nephropathy being, respectively, 12.0-26.7 and 3.9-4.2 times as high above as below cut off points which minimised overlap (two hour plasma glucose concentration 12.6 mmol/l; fasting plasma glucose concentration 9.3 mmol/l; glycated haemoglobin (HbA1c) concentration 7.8%). Longitudinally, each of the three measures of glycaemia significantly predicted the development of retinopathy (P < 0.0001) and nephropathy (P < 0.05). Receiver operating characteristic curves showed that two hour plasma glucose concentration was superior to fasting plasma glucose concentration (P < 0.05) for prevalent cases of retinopathy, but otherwise no variable had a significant advantage for detecting incident or prevalent cases of either complication.

CONCLUSIONS

These findings suggest that determination of glycated haemoglobin or fasting plasma glucose concentrations alone may be acceptable alternatives to measuring glucose concentration two hours after challenge with 75 g glucose for the diagnosis of diabetes.

Birth weight and non-insulin dependent diabetes: thrifty genotype, thrifty phenotype, or surviving small baby genotype?

OBJECTIVE

To determine the prevalence of diabetes in relation to birth weight in Pima Indians.

DESIGN

Follow up study of infants born during 1940-72 who had undergone a glucose tolerance test at ages 20-39 years.

SETTING

Gila River Indian community, Arizona.

SUBJECTS

1179 American Indians.

MAIN OUTCOME MEASURE

Prevalence of non-insulin dependent diabetes mellitus (plasma glucose concentration > or = 11.1 mmol/l two hours after ingestion of carbohydrate).

RESULTS

The prevalence was greatest in those with the lowest and highest birth weights. The age adjusted prevalences for birth weights < 2500 g, 2500-4499 g, and > or = 4500 g were 30%, 17%, and 32%, respectively. When age, sex, body mass index, maternal diabetes during pregnancy, and birth year were controlled for, subjects with birth weights < 2500 g had a higher rate than those with weights 2500-4499 g (odds ratio 3.81; 95% confidence interval 1.70 to 8.52). The risk for subsequent diabetes among higher birthweight infants (> or = 4500 g) was associated with maternal diabetes during pregnancy. Most diabetes, however, occurred in subjects with intermediate birth weights (2500-4500 g).

CONCLUSIONS

The relation of the prevalence of diabetes to birth weight in the Pima Indians is U shaped and is related to parental diabetes. Low birth weight is associated with non-insulin dependent diabetes. Given the high mortality of low birthweight infants selective survival in infancy of those genetically predisposed to insulin resistance and diabetes provides an explanation for the observed relation between low birth weight and diabetes and the high prevalence of diabetes in many populations.

Obesity in Pima Indians: genetic segregation analyses of body mass index complicated by temporal increases in obesity

During the past half-century the prevalence of obesity in developed countries has increased greatly. Such short-term changes in prevalence must be environmentally determined, but genes can mediate response to environmental change, for example, through variable gene penetrance and expression. Obesity differences between bith cohorts complicate the interpretation of phenotypic comparisons between generations that span periods of change. Genetic segregation analyses of the body mass index in 618 Pima Indian nuclear families (2 generations) identified recessive major gene inheritance, which is the same pattern of transmission that has been found in several other populations. However, within-birth-cohort analyses of siblings (one generation) uniformly supported codominant major gene inheritance with no polygenic heritability. For untransformed data transmission probabilities were Mendelian in the later-born cohort and in the combined sample of siblings. After transformation to remove skewness, transmission probabilities were Mendelian only in the earlier-born cohort (i.e., those siblings born before a period of marked temporal increase following World War II). A higher penetrance of codominant obesity susceptibility genes in the younger generation would result in some genetically obese individuals who have no affected parents, thus simulating recessive inheritance. Taken together, the results of these analyses suggest that the recessive pattern we identified in the Pima Indian nuclear families could be accounted for by temporal changes in penetrance of codominant obesity-predisposing genes. By implication, more modest temporal increases in white and black populations could in part account for the recessive pattern of inheritance described by several investigators.

Glycated haemoglobin predicts progression to diabetes mellitus in Pima Indians with impaired glucose tolerance

Glycated haemoglobin could offer several practical advantages over the OGTT for assessing glucose metabolism. Initial cross-sectional studies (1983-1985) on 381 subjects (mostly Pima Indians) described the relationship between HbA1c (a specific glycated Hb) and the OGTT. We performed follow-up OGTTs and HbA1c measurements on 257 of these same subjects 1.6-6.1 years later. Subjects were again grouped according to both the result of the OGTT (normal, IGT or diabetes, by WHO criteria) and HbA1c result (normal or elevated based on mean +/- 1.96 SD of normal). Of 66 subjects with IGT at baseline, 47 (71%) had normal HbA1c and 19 (29%) had elevated HbA1c. Twenty-six (39%) of these subjects had diabetes at follow-up. Of these subjects with IGT, a significantly greater percentage of subjects with elevated HbA1c at baseline (68%) showed worsening to diabetes than those with a normal HbA1c (28%); (chi-square = 7.8, df = 1, p < 0.01). Thus, in subjects with IGT, glycated Hb may be a useful predictor of progression to diabetes.

Obesity in Pima Indians: large increases among post-World War II birth cohorts

Several studies have shown secular increases in obesity during the past 35 years, and others have reported increases in dietary fat consumption during the same period. Here we report a dramatic increase in obesity among Pima Indians born after World War II that appears to be associated with increased exposure to Western customs and diet following 1945. We examined the body mass index (BMI = weight in kilograms/height2 in meters) of 1,128 male and 1,372 female Pima Indians aged 15-65 years who were born between 1901 and 1964 and were examined between 1965 and 1990. We found large increases in BMI among Pima Indian men and women in post-World War II birth cohorts (1945 and later). The parallel changes in body mass index, dietary fat, and exposure to Western culture following World War II suggest that culturally mediated changes in diet and level of physical activity associated with modern industrialized society may have led to the large increases in obesity in the Pima Indians and to smaller parallel changes observed worldwide in westernized countries.

Comparison of screening tests for non-insulin-dependent diabetes mellitus

BACKGROUND

Screening for non-insulin-dependent diabetes mellitus (NIDDM) can be useful in clinical practice and in epidemiologic and genetic studies, but the available information for choosing between screening methods is limited. In this study, characteristics of several screening tests for NIDDM were compared.

METHODS

Among Pima Indians participating in an epidemiologic study, the sensitivity and specificity for detecting NIDDM of fasting plasma glucose (FPG) levels and two measures of glycated hemoglobin (HbA1 or HbA1c) were compared in 2092 fasting subjects. Glycated hemoglobin, quantitative glycosuria, and dipstick glycosuria were compared in 237 nonfasting subjects. Diabetes was diagnosed using an oral glucose tolerance test if the 2-hour postload venous plasma glucose concentration was 11.1 mmol/L (200 mg/dL) or greater. The area under the relative operating characteristic curve was used to compare tests.

RESULTS

In fasting subjects, the sensitivity for detecting diabetes with 98% specificity was 78.8% for HbA1 level of 7.5% or greater, 80.3% for HbA1c level of 6.3% or greater, and 88.0% for FPG level of 6.83 mmol/L (123 mg/dL) or greater. By relative operating characteristic analysis, there were no significant differences between FPG and HbA1c, but FPG was significantly more sensitive than HbA1. In nonfasting subjects the sensitivity at 98% specificity was 92.9% for HbA1 level of 7.3% or greater, 80.6% for quantitative urine glucose level of 1.94 mmol/L (35 mg/dL) or greater, and 64.3% for trace or greater of dipstick glycosuria. The area under the relative operating characteristic curve was significantly greater for glycated hemoglobin than for either measure of glycosuria.

CONCLUSIONS

Although FPG has the best screening properties, HbA1c, HbA1, and quantitative urine glucose also provide high specificity and approximately 80% sensitivity in detecting NIDDM. The choice of a particular method could depend on cost, convenience, and availability.

Pre-diabetic blood pressure predicts urinary albumin excretion after the onset of type 2 (non-insulin-dependent) diabetes mellitus in Pima Indians

Blood pressure was measured in 490 non-proteinuric Pima Indians from the Gila River Indian Community in Arizona at least 1 year before the diagnosis of Type 2 (non-insulin-dependent) diabetes mellitus. Urine albumin concentration was measured in the same subjects 0-24 years (mean 5 years) after diabetes was diagnosed. Prevalence rates of abnormal albumin excretion (albumin-to-creatinine ratio > or = 100 mg/g) after the onset of Type 2 diabetes were 9%, 16%, and 23%, respectively, for the lowest to highest tertiles of pre-diabetic mean blood pressure. When controlled for age, sex, duration of diabetes and pre-diabetic 2-h post-load plasma glucose concentration, higher pre-diabetic mean blood pressure predicted abnormal urinary excretion of albumin after the onset of diabetes. This finding suggests that the higher blood pressure seen in diabetic nephropathy is not entirely a result of the renal disease, but may precede and contribute to it.

Determinants of end-stage renal disease in Pima Indians with type 2 (non-insulin-dependent) diabetes mellitus and proteinuria

To identify factors related to the development of end-stage renal disease after the onset of proteinuria, its incidence was determined in 364 Pima Indians aged 35 years or older with Type 2 (non-insulin-dependent) diabetes mellitus and proteinuria (protein-to-creatinine ratio > or = 0.5 g/g). Of these 364 subjects, 95 (36 men, 59 women) developed end-stage renal disease. The cumulative incidence was 40% 10 years after and 61% 15 years after the onset of proteinuria. The incidence of end-stage renal disease was significantly related to the duration of diabetes, the duration of proteinuria, higher 2-h plasma glucose concentration, type of diabetes treatment, and the presence of retinopathy at the time of recognition of the proteinuria, but not to age, sex, or blood pressure. Duration of proteinuria influenced the risk of end-stage renal disease, contingent, however, upon the duration of diabetes at the onset of proteinuria. The higher cumulative incidence of end-stage renal disease 15 years after the onset of proteinuria in Pima Indians (61%) than in Caucasians from Rochester, Minnesota (17%) may be attributable, in part, to the younger age of onset of Type 2 diabetes in Pima Indians than in Caucasians, to ethnic differences in susceptibility to renal disease, or to lower death rates among the Pima Indians from competing causes of death, such as coronary heart disease.

The association of physical activity with obesity, fat distribution and glucose intolerance in Pima Indians

The relationships between physical activity, obesity, fat distribution and glucose tolerance were examined in the Pima Indians who have the highest documented incidence of non-insulin-dependent diabetes. Fasting and 2-h post-load plasma glucose concentrations, body mass index, and waist-to-thigh circumference ratios were determined in 1054 subjects aged 15-59 years. Current (during the most recent calendar year) and historical (over a lifetime) leisure and occupational physical activity were determined by questionnaire. Current physical activity was inversely correlated with fasting and 2-h plasma glucose concentrations, body mass index and waist-to-thigh ratios for most sex-age groups even when diabetic subjects were excluded. Controlled for age, obesity and fat distribution, activity remained significantly associated with 2-h plasma glucose concentrations in males. In subjects aged 37-59 years, individuals with diabetes compared to those without reported significantly less leisure physical activity during the teenage years (median hours per week of activity, 9.1 vs 13.2 for men; 1.0 vs 2.2 for women). Controlled for body mass index, sex, age and waist-to-thigh ratio, subjects who reported low levels of historical leisure physical activity had a higher rate of diabetes than those who were more active. In conclusion, current physical activity was inversely related to glucose intolerance, obesity and central distribution of fat, particularly in males. Subjects with diabetes were currently less active and reported less historical physical activity than non-diabetic subjects. These findings suggest that activity may protect against the development of non-insulin-dependent diabetes both directly and through an influence on obesity and fat distribution.

Rheumatoid arthritis and mortality. A longitudinal study in Pima Indians

OBJECTIVE

To determine the effect of rheumatoid arthritis (RA) on mortality rates.

METHODS

Longitudinal analyses of data from a cohort of Pima Indians from the Gila River Indian Community in Arizona, who were followed up during the period February 1965 through December 1989.

RESULTS

Among 2,979 study subjects aged > or = 25 years, there were 858 deaths, 79 of which occurred in subjects with RA (36 men, 43 women). Age- and sex-adjusted mortality rates were slightly higher in subjects with RA than in those without (mortality rate ratio 1.28, 95% confidence interval [95% CI] 1.01-1.62). Among those with RA, mortality rates were higher in older subjects (mortality rate ratio 1.51 per 10-year increase in age, 95% CI 1.22-1.88), in male subjects (mortality rate ratio 2.23, 95% CI 1.44-3.45, adjusted for age), and in subjects with proteinuria (mortality rate ratio 1.88, 95% CI 1.02-3.46, adjusted for age and sex). Mortality rate ratios for these risk factors were similar in subjects without RA. In addition, among subjects with RA, rheumatoid factor (RF) positivity was predictive of death (mortality rate ratio 1.94, 95% CI 1.10-3.43), and the excess mortality was found primarily among subjects who were seropositive. The death rate from cardiovascular disease (mortality rate ratio 1.77, 95% CI 1.10-2.84) and from liver cirrhosis or other alcohol-related disease (mortality rate ratio 2.52, 95% CI 1.06-6.01) was increased in persons with RA.

CONCLUSION

The results of this population-based study suggest that although the risk of mortality in subjects with RA is significantly higher than in those without RA, the risk ratio is in the lower range of that described previously in studies of clinic-based cohorts. RF positivity as a predictor of early death among subjects with RA indicates that the immunologic processes in seropositive RA may contribute to the events that eventually lead to early death.

Glycated haemoglobin, plasma glucose and diabetic retinopathy: cross-sectional and prospective analyses

Among Pima Indians with Type 2 (non-insulin-dependent) diabetes mellitus the relationships between glycated haemoglobin (HbA1), fasting or 2-h post-load plasma glucose and diabetic retinopathy were examined by cross-sectional and prospective analyses, and the strengths of the associations were directly compared by receiver operating characteristic analysis. In the cross-sectional analysis, HbA1, fasting and 2-h plasma glucose were each significantly related to retinopathy among 789 diabetic subjects by separate logistic models. In a stepwise multiple logistic model in which HbA1, fasting and 2-h plasma glucose were included, HbA1 was selected as having the strongest association with retinopathy and neither fasting nor 2-h plasma glucose contributed significantly to the model once HbA1 was entered. Similarly, in the prospective analysis, HbA1, fasting and 2-h plasma glucose all predicted retinopathy in 227 diabetic subjects by separate proportional-hazards models. In a stepwise proportional-hazards model with HbA1, fasting and 2-h plasma glucose available to the model, HbA1 was again selected as having the strongest association with the incidence of retinopathy, and neither fasting nor 2-h plasma glucose significantly added to the prediction of retinopathy. A receiver operating characteristic analysis was used to determine if HbA1 was statistically significantly better than fasting or 2-h plasma glucose in assessing the risk for retinopathy. In neither the cross-sectional nor the prospective data did the area under the receiver operating characteristic curve for HbA1 differ significantly from that for fasting or 2-h plasma glucose (p > 0.05 for each).(ABSTRACT TRUNCATED AT 250 WORDS)

Insulinemia in children at low and high risk of NIDDM

OBJECTIVE

Fasting hyperinsulinemia in the presence of normoglycemia usually indicates insulin resistance and is characteristic of populations at high risk for developing NIDDM. Hyperinsulinemia predicts the development of impaired glucose tolerance and NIDDM in Pima Indians, a population with a high incidence of NIDDM. Insulin concentrations in population-based samples of children who have different risks of developing NIDDM later in life have not been reported previously.

RESEARCH DESIGN AND METHODS

We compared fasting insulin concentrations in two populations of nondiabetic children, 6-19 yr of age: Pima Indians from southern Arizona and Caucasians from Minnesota.

RESULTS

Insulin concentration varied with age, sex, glucose concentration, and relative weight. Mean fasting insulin concentration was 140.3 pM in Pima Indian males, 94.4 pM in Caucasian males, 171.5 pM in Pima Indian females, and 107.1 pM in Caucasian females. For each sex, the mean fasting insulin concentration, controlled for age, glucose, and relative weight, was significantly higher in the Pima Indians than in the Caucasians (P < 0.001).

CONCLUSIONS

From a young age, Pima Indian children have higher fasting insulin concentrations than Caucasian children. As hyperinsulinemia predicts subsequent NIDDM, these data suggest that the susceptibility to NIDDM is manifest at a young age as fasting hyperinsulinemia.

Development of impaired glucose tolerance with or without weight gain

OBJECTIVE

To evaluate whether risk factors and changes in insulin concentrations differ in subjects who develop impaired glucose tolerance with or without weight gain. Hyperinsulinemia is a risk factor for impaired glucose tolerance, and insulin concentrations increase further with the development of impaired glucose tolerance. Its development, however, often is accompanied by weight gain, which, by itself, is associated with high insulin concentrations.

RESEARCH DESIGN AND METHODS

Participants for this study were adult Pima Indians involved in an ongoing epidemiological study. Initially, all had normal glucose tolerance. During follow-up, 80 of 387 who did not gain weight developed impaired glucose tolerance, as did 295 of 1026 who gained weight. Risk factors for impaired glucose tolerance and the relationships between changes in weight and glucose and changes in insulin were evaluated by multivariate analyses.

RESULTS

High baseline fasting insulin predicted impaired glucose tolerance regardless of weight after adjustment for age, sex, body mass index, and glucose. The development of impaired glucose tolerance was accompanied by a further increase in fasting and 2-h insulin, whether or not subjects gained weight. In both weight-change groups, impaired glucose tolerance was associated with more centralized fat distribution.

CONCLUSIONS

Fasting hyperinsulinemia, a reflection of insulin resistance, is associated with the risk of developing impaired glucose tolerance whether or not weight is gained. Impaired glucose tolerance occurs when insulin resistance increases further. Weight gain is the most common precipitating factor. Aging and physical inactivity are other possible precipitating factors.

Increased mortality with gallstone disease: results of a 20-year population-based survey in Pima Indians

OBJECTIVE

To determine if gallstone disease is associated with an increased risk for malignancy and higher total mortality in Pima Indians.

DESIGN

Inception cohort.

SETTING

American Indian community.

PARTICIPANTS

Age- and sex-stratified random population-based sample.

MEASUREMENTS

Between 1966 and 1969, an age- and sex-stratified random sample of Pima Indians from the Gila River Indian Community in Arizona was examined to identify evidence of gallstone disease defined as either gallstones (oral cholecystography) or previous cholecystectomy. During 20 years of follow-up, deaths were recorded and underlying causes of death, according to death certificates, were determined.

RESULTS

Among 383 persons with known gallbladder status, 186 (49%) died: 133 among the 222 persons with gallstone disease and 53 among the 161 without. The overall death rate was higher in persons with gallstone disease than in those with normal gallbladders. The age- and sex-adjusted death rate ratio was 1.9 (95% Cl, 1.3 to 2.7). Furthermore, the death rate attributed to malignancies was 6.6 times (Cl, 1.3 to 33.1) as high in persons with gallstone disease as in those with normal gallbladders. Of the 20 fatal malignancies in persons with gallstone disease, 11 occurred in the digestive tract, of which six involved the gallbladder or bile ducts.

CONCLUSIONS

Increased cancer mortality and total mortality were found in Pima Indians with gallstone disease. Although plausible explanations exist for the increased cancer mortality, the increased death rates due to other causes are unexplained. Whether cholecystectomy would change this risk is unknown.

Diabetes and obesity in the offspring of Pima Indian women with diabetes during pregnancy

OBJECTIVE

To review the long-term effects of the diabetic pregnancy on the offspring among the Pima Indians of Arizona.

RESEARCH DESIGN AND METHODS

Studies published by the Phoenix Epidemiology and Clinical Research branch of the National Institute of Diabetes and Digestive and Kidney Diseases, since the inception of the longitudinal diabetes studies in 1965 were reviewed. In addition, pertinent studies from other centers, mentioned as references in these publications, were reviewed. As far as possible, all original articles and abstracts on this aspect of the Pima Indian studies were discussed.

RESULTS

The offspring of women who had diabetes during pregnancy, on average, were more obese and had higher glucose concentrations and more diabetes than the offspring of women who developed diabetes after pregnancy or who remained nondiabetic. Although no new analyses were attempted, several of the older publications were updated by repeating the analyses on later, expanded data sets.

CONCLUSIONS

The diabetic pregnancy, in addition to its effects on the newborn, has effects on the subsequent growth and glucose metabolism of the offspring. These effects are in addition to genetically determined traits.

Determinants of diabetes mellitus in the Pima Indians

OBJECTIVE

To review the research findings on the determinants of diabetes mellitus in Pima Indians.

RESEARCH DESIGN AND METHODS

Pima Indians in Arizona have participated in a longitudinal diabetes study that has provided data on and hypotheses about the development of NIDDM. Findings from this study are reviewed and updated.

RESULTS

Frequency distributions of plasma glucose and HbA1 are bimodal in Pima adults, and substantial risk of the specific vascular complications of diabetes is confined to those in the higher components of these distributions. These findings contributed to the adoption of internationally recognized criteria for classification of glucose tolerance. Diabetes in the Pimas is strongly familial, and probably of genetic origin, although the precise nature of the gene or genes involved remains unknown. Obesity, which is at least in part environmentally determined, is a major factor interacting with the presumed genetic susceptibility to result in diabetes. The incidence of diabetes in the Pimas has increased during the last several decades, providing further evidence for environmental-genetic interaction. Longitudinal studies suggest that the progression from normal to diabetes can be considered to involve two stages. The first, primarily attributable to insulin resistance, leads to impaired glucose tolerance, and the second, which depends on insulin secretory failure, leads to worsening hyperglycemia and overt diabetes.

CONCLUSIONS

The Pimas and many other American Indian populations suffer from a high incidence of diabetes and its characteristic disabling or fatal complications, and would benefit from continued research on the pathogenesis and prevention of the disease.

Diabetic kidney disease in Pima Indians

OBJECTIVE--To describe the natural history of kidney disease in Pima Indians with NIDDM. RESEARCH DESIGN AND METHODS--Review of previous studies describing diabetic kidney disease in this Native-American population and in other populations. RESULTS--NIDDM is the leading cause of renal failure in Pima Indians, among whom the incidence of ESRD is 23 times that of the general U.S. population. The high incidence of NIDDM and its early onset in the Pima undoubtedly contribute to this difference. The incidence of overt nephropathy and ESRD, as a function of diabetes duration, is at least as high in Pima Indians with NIDDM as that reported in other populations with IDDM. Furthermore, nearly all of the excess mortality associated with NIDDM is found in individuals with overt nephropathy. Mild elevations of UAE, which may be present even shortly after the onset of diabetes, predict the development of overt nephropathy in diabetic Pimas. Additional predictors include high blood pressure, level of glycemia, duration of diabetes, family history of diabetic nephropathy, and type of diabetes treatment. CONCLUSIONS--Diabetic kidney disease is a major cause of morbidity and mortality in Pima Indians. The natural history of diabetic kidney disease in this population is similar, in many ways, to the natural history described in individuals with IDDM.

Obesity in Pima Indians. Distribution characteristics and possible thresholds for genetic studies

We examined distribution characteristics of the body mass index (BMI; weight/height; kg/m2) in a sample of 1128 male and 1372 female Pima Indians aged 15-65 years. We found that women had a higher mean and variance of BMI than men. From commingling analyses, we determined that the distribution of BMI could be accounted for either by a single skewed distribution or by a mixture of multiple normal components. These component distributions may be used to define provisional thresholds in selecting families for genetic studies. To ensure genetic segregation of obesity predisposing genes in Pima families will require that some members have BMIs > or = 40 kg/m2.

Insulin treatment, endogenous insulin concentration, and ECG abnormalities in diabetic Pima Indians. Cross-sectional and prospective analyses

The prevalence and incidence of CHD, defined by ECG abnormalities according to the Tecumseh criteria for Minnesota Codes, were determined in Pima Indians greater than or equal to 25 yr of age. In a cross-sectional analysis, the age-sex-adjusted prevalence (+/- SE) of ECG abnormalities was higher in 1454 NIDDM patients (6.86 +/- 0.65%) than in 1696 nondiabetic subjects (3.23 +/- 0.63%; prevalence rate ratio = 2.12; 95% CI 1.39-3.25). In a prospective analysis, the age-sex-adjusted incidence (+/- SE) of ECG abnormalities was higher in 824 NIDDM patients (12.77 +/- 1.67) than in 935 nondiabetic subjects (5.93 +/- 1.43 cases/1000 person-yr; incidence rate ratio = 2.15; 95% CI 1.26-3.69). The prevalence of ECG abnormalities in insulin-treated NIDDM patients was significantly higher than in NIDDM patients not treated with insulin (age-sex-adjusted OR = 2.83; 95% CI 1.84-4.33); and this association persisted when adjusted for other factors such as sBP, BMI, duration of diabetes, serum cholesterol concentration, and oral hypoglycemic agents (OR = 2.12; 95% CI 1.34-3.37). In the prospective analysis, the incidence of ECG abnormalities in NIDDM patients treated with insulin was higher than in those NIDDM patients not treated with insulin, but, when controlled for age, sex, duration of diabetes, and oral hypoglycemic agents in a proportional-hazards model, the relationship with insulin treatment was not statistically significant (incidence rate ratio = 1.36; 95% CI 0.80-2.31). This suggests that insulin treatment may be a marker of more severe diabetes, and that factors associated with clinical indications for insulin treatment, rather than insulin treatment per se, are related causally to CHD. On the other hand, endogenous fasting and 2-h postload serum insulin concentrations were not associated with ECG abnormalities among 761 NIDDM patients not treated with insulin nor among 1226 nondiabetic subjects. Furthermore, in the prospective study, neither endogenous fasting nor 2-h postload serum insulin was associated with the subsequent development of ECG abnormalities in NIDDM patients or nondiabetic subjects.

The magnitude and origin of European-American admixture in the Gila River Indian Community of Arizona: a union of genetics and demography

Complementary genetic and demographic analyses estimate the total proportion of European-American admixture in the Gila River Indian Community and trace its mode of entry. Among the 9,616 residents in the sample, 2,015 persons claim only partial Native American heritage. A procedure employing 23 alleles or haplotypes at eight loci was used to estimate the proportion of European-American admixture, m(a), for the entire sample and within six categories of Caucasian admixture calculated from demographic data, md. The genetic analysis gave an estimate of total European-American admixture in the community of 0.054 (95% confidence interval [CI] .044-.063), while an estimate from demographic records was similar, .059. Regression of m(a) on md yielded a fitted line m(a) = .922md, r = .959 (P = .0001). When total European-American admixture is partitioned between the contributing populations, Mexican-Americans have provided .671, European-Americans .305, and African-Americans .023. These results are discussed within the context of the ethnic composition of the Gila River Indian Community, the assumptions underlying the methods, and the potential that demographic data have for enriching genetic measurements of human admixture. It is concluded that, despite the severe assumptions of the mathematical methods, accurate, reliable estimates of genetic admixture are possible from allele and haplotype frequencies, even when there is little demographic information for the population.

Duration of obesity increases the incidence of NIDDM

The effect of duration of obesity on incidence of non-insulin-dependent diabetes mellitus (NIDDM) was determined among Pima Indians. Duration of obesity was defined as the time since body mass index (BMI) was first known to be at least 30 kg/m2. Among 1057 participants eligible for study, there were 224 incident cases of NIDDM in 5975 person-yr of follow-up. The association of duration of obesity with incidence of diabetes adjusted for age, sex, and current BMI was highly significant (P less than 0.0001). This adjusted incidence of diabetes in cases/1000 person-yr of obesity was 24.8 for people with less less than 5 yr of obesity, 35.2 for people with 5-10 yr of obesity, and 59.8 for people with at least 10 yr of obesity. There was no apparent excess risk of diabetes for people who had a BMI of at least 30 kg/m2 and then lost weight. They had a slightly nonsignificantly higher rate than people who had not attained a BMI of at least 30 kg/m2 and a lower rate than people whose BMI remained 30-35 kg/m2. The relationship of duration of obesity with serum insulin concentrations among nondiabetic people was determined controlling for sex and age, BMI, and plasma glucose concentrations at the time of a glucose tolerance test. Duration of obesity was inversely associated with fasting serum insulin concentration through most of the range of fasting plasma glucose concentrations (P less than 0.001) and tended to be inversely associated with 2-h postload serum insulin concentration through the entire range of postload plasma glucose concentrations (P = 0.058).

Abnormal glucose tolerance during pregnancy in Pima Indian women. Long-term effects on offspring

The long-term effects on offspring of abnormal glucose tolerance detected during pregnancy were examined in 552 Pima Indian offspring 5-24 yr of age. Fasting hyperinsulinemia, presumably reflecting increased insulin resistance, occurred at an earlier age in the offspring of women who had abnormal glucose tolerance during pregnancy, and these offspring were more obese and had higher rates of abnormal glucose tolerance. When confounding factors were controlled, a 1 mM higher 2-h postload glucose concentration during pregnancy resulted in a significantly higher prevalence of diabetes in the offspring (odds ratio = 162). Maternal 2-h glucose concentration during pregnancy was also a significant predictor of glucose concentration during pregnancy in the offspring (P = 0.011). Thus, the metabolic abnormalities associated with the diabetic pregnancy result in long-term effects on the offspring, including insulin resistance, obesity, and diabetes, which in turn may contribute to transmission of risk for developing the same problems in the next generation.

Assessment of risk of overt nephropathy in diabetic patients from albumin excretion in untimed urine specimens

The ability of an albumin-to-creatinine ratio, measured in a single untimed urine specimen, to indicate the likelihood of developing overt diabetic nephropathy was determined in 439 Pima Indians (134 men, 305 women) aged 25 years or older with non-insulin-dependent diabetes. During a mean follow-up period of 4.2 years, 59 (13%) of the subjects developed overt nephropathy, 47 (80%) of whom had albumin-to-creatinine ratios of 30 mg/g or greater at baseline. Subjects with albumin-to-creatinine ratios of 30 to 299 mg/g (a level of excretion often termed "microalbuminuria") had 9.2 times (95% confidence interval, 4.4 to 21.4) the incidence of overt nephropathy of those with ratios of less than 30 mg/g. Furthermore, the albumin-to-creatinine ratio remained a strong predictor of overt nephropathy even when controlled for age, sex, diabetes duration, mean blood pressure, and 2-hour postload plasma glucose concentration with a proportional-hazards function analysis. Thus, an albumin-to-creatinine ratio measured in a single untimed urine specimen is an effective means of identifying diabetic subjects who are at risk of developing overt nephropathy that could replace the more traditional timed urine collections.

Obesity in the Pima Indians: its magnitude and relationship with diabetes

Members of the Pima Indian population are obese, on average, as estimated by the body mass index (BMI). Young adults have had the highest BMIs and there have been modest increases in age- and sex-specific mean BMIs for the past 25 y. These observations suggest that the older adults have had less exposure to factors leading to obesity than have the younger adults. Compared with children studied early in this century, present-day Pima children are much heavier for height, suggesting that the degree of obesity has increased since that time. Obesity in the Pimas is familial and has complex relationships with non-insulin-dependent diabetes mellitus, a common disease in this population. Obesity predicts the development of diabetes; once people have diabetes, however, they tend to lose weight. Thus, obesity should not be studied in this population without also considering diabetes, which tends to limit the degree of obesity.

A two-step model for development of non-insulin-dependent diabetes

Both insulin resistance and beta-cell dysfunction occur during the development of non-insulin-dependent diabetes mellitus (NIDDM), but controversy exists about which lesion is primary. Based on longitudinal studies in the Pima Indians, a population with the world's highest reported prevalence of NIDDM, a two-step model for development of the disease is proposed. The first step is transition from normal to impaired glucose tolerance, for which insulin resistance is the main determinant, and the second and later step is worsening from impaired glucose tolerance to diabetes, in which beta-cell dysfunction plays a critical role. This hypothesis is consistent with findings from other ethnic groups from many parts of the world.

Insulin and hypertension. Relationship to obesity and glucose intolerance in Pima Indians

The relationships among blood pressure, obesity, glucose tolerance, and serum insulin concentration were studied in 2873 Pima Indians aged 18-92 yr (mean 37 yr). Age- and sex-adjusted to the Pima population, the prevalence of hypertension (systolic blood pressure greater than or equal to 160 mmHg, diastolic blood pressure greater than or equal to 95 mmHg, or receiving drug treatment) was 7.1% for subjects with normal glucose tolerance compared with 13.0% for subjects with impaired glucose tolerance (IGT) and 19.8% for those with non-insulin-dependent diabetes mellitus (NIDDM) (P less than 0.001). The prevalence ratio of hypertension was 1.8 (95% confidence interval [CI] 1.2-2.5) for IGT and 2.6 (95% CI 2.0-3.2) for NIDDM compared with normal glucose tolerance, controlled for age, sex, and body mass index (BMI). In logistic regression analysis, hypertension was positively related to age, male sex, BMI, glucose tolerance, and fasting but not 2-h postload serum insulin concentration. Among subjects not taking antihypertensive drugs, however, neither fasting nor 2-h postload serum insulin was significantly related to hypertension. Furthermore, in 2033 subjects receiving neither antihypertensive nor antidiabetic drugs, blood pressure was not significantly correlated to fasting insulin concentration, and 2-h postload serum insulin was negatively correlated with diastolic blood pressure. In conclusion, insulin is not significantly related to blood pressure in Pima Indians not receiving antihypertensive drugs. Higher insulin concentrations in drug-treated hypertensive patients might result from the treatment rather than contribute to the pathogenesis of hypertension. Thus, these data do not support a major role for insulin in determining the occurrence of hypertension or regulation of blood pressure in Pima Indians.

Type 2 diabetes mellitus and periodontal disease

The relationship between type 2 diabetes mellitus and periodontal disease was evaluated in 2,878 Pima Indians of the southwestern United States. Two independent measures of periodontal disease, probing attachment loss and radiographic bone loss, were used to compare prevalence and severity of periodontal disease in diabetic and nondiabetic subjects. In all age groups studied, subjects with diabetes had a higher prevalence of periodontal disease, indicating that diabetes may be a risk factor for periodontal disease.