Plasma lipoproteins and the incidence of abnormal excretion of albumin in diabetic American Indians: the Strong Heart Study

Animal studies suggest that lipids are risk factors for kidney diseases. Some prospective studies and clinical trials have reported predictive effects of lipoproteins on different stages of diabetic nephropathy in humans. We examined lipoprotein abnormalities to determine if they predict abnormal urinary excretion of albumin (> or = 30 mg albumin/g creatinine), using logistic regression. We followed 671 American Indians (211 men, 460 women) with Type II diabetes for a mean of 3.9 years (range 1.7-6.2). Participants were aged 45-74 years. They had normal excretion of albumin and normal serum creatinine at baseline. 67 men and 144 women developed abnormal excretion of albumin. In models controlled for age, treatment with oral hypoglycaemic agents or insulin, HbA1c, study site, degree of Indian heritage, mean arterial blood pressure, albumin excretion at baseline and duration of diabetes, a high HDL cholesterol was a protector for abnormal excretion of albumin in women [odds ratio (OR) comparing the 90th with the 10th percentile = 0.56, 95% confidence interval (CI) = 0.32-0.98], but not in men (OR = 1.5, 95% CI = 0.66-3.4). Further adjustment for obesity, insulin concentration, alcohol consumption or physical activity did not change the results. There was a tendency for high values of VLDL and total triglyceride and small LDL size to predict abnormal excretion of albumin in women only. We conclude that low HDL cholesterol was a risk factor for abnormal excretion of albumin in women, but not in men. Sex hormones may be responsible for sex differences in the association between HDL cholesterol and abnormal excretion of albumin.

Increasing prevalence of Type II diabetes in American Indian children

Until recently, Type II diabetes was considered rare in children. The disease is, however, increasing among children in populations with high rates of Type II diabetes in adults. The prevalence of Type II diabetes was determined in 5274 Pima Indian children between 1967 and 1996 in three 10-year time periods, for age groups 5-9, 10-14 and 15-19 years. Diabetes was diagnosed using World Health Organisation criteria, based on an oral glucose tolerance test. The prevalence of diabetes increased over time in children aged 10 years and over: in boys from 0 % in 1967-1976 to 1.4% in 1987-1996 in the 10-14 year old age group, and from 2.43% to 3.78% for age group 15-19 and in girls from 0.72 % in 1967-1976 to 2.88 % in 1987-1996 in the 10-14 year old age group, and from 2.73 % to 5.31 % for age group 15-19 years. Along with the increase in the prevalence of Type II diabetes (p < 0.0001), there was an increase in weight (calculated as percentage of relative weight, p < 0.0001), and in frequency of exposure to diabetes in utero (p < 0.0001). The increasing weight and increasing frequency of exposure to diabetes in utero accounted for most of the increase in diabetes prevalence in Pima Indian children over the past 30 years. Type II diabetes is now a common disease in American Indian children aged 10 or more years and has increased dramatically over time, along with increasing weight. A vicious cycle related to an increase in the frequency of exposure to diabetes in utero appears to be an important feature of this epidemic.

Long-term effects of the intrauterine environment, birth weight, and breast-feeding in Pima Indians

The objectives of this study were to evaluate the long-term effect of the diabetic pregnancy on Pima Indian offspring and to see how the prevalence of diabetes during pregnancy is influenced by early life events, such as birth weight and type of infant feeding, that are known to influence the prevalence of diabetes in nonpregnant Pima adults. A modified 75-g oral glucose tolerance test was administered to women during each pregnancy. These women and, from the age of 5 years, their children were followed biennially with a standardized examination that includes measurement of height and weight and a standard 75-g oral glucose tolerance test administered in the morning after an overnight fast. We found that diabetes during pregnancy is a major risk factor for diabetes and hyperglycemia in the offspring. Diabetes in the next generation is less common among breast-fed children (6.9 and 30.1% among offspring of nondiabetic and diabetic women, respectively) than among bottle-fed children (11.9 and 43.6%, respectively). The prevalence of diabetes during pregnancy is influenced by conditions, such as birth weight, known to influence the prevalence of diabetes in this population in general. The highest rates of diabetes during pregnancy at 25-34 years of age (25%) were found among women with a birth weight below 2.5 kg. The infant of the woman with diabetes during pregnancy is at risk of becoming obese and of developing type 2 diabetes at a young age. The prevalence of diabetes in women of childbearing age is influenced by factors occurring early in life (i.e., birth weight and type of infant feeding). Whether or not the long-term adverse outcomes, including diabetic pregnancies in the next generation, can be lessened or prevented by meticulous control of diabetes during pregnancy, careful attention to intrauterine growth, or more general infant breast-feeding remains unknown.

Sib-pair linkage analysis for susceptibility genes for microvascular complications among Pima Indians with type 2 diabetes. Pima Diabetes Genes Group

The aim of this study was to identify loci influencing susceptibility to microvascular complications (nephropathy and retinopathy) in Pima Indians with type 2 diabetes. Affected sib-pair linkage analyses were performed on 98 diabetic sibling pairs with nephropathy in both members and on 103 sibling pairs with retinopathy in both members. Four chromosomal regions with some evidence of linkage (P < 0.01; logarithm of odds [LOD] >1.18) with nephropathy were identified. The strongest evidence for linkage with nephropathy was on chromosome 7, where two adjacent markers, D7S500 and D7S1804, were linked both by two-point analysis (LOD = 2.73 and LOD = 2.28; respectively) and by multipoint analysis (LOD = 2.04). Additional loci potentially linked to nephropathy were found on chromosome 3, near D3S3053 (multipoint LOD = 1.48); on chromosome 9, near D9S910 (multipoint LOD = 1.12) and D9S302 (two-point LOD = 1.28); and on chromosome 20, near D20S115 (multipoint LOD = 1.83) and GATA65E01 (two-point LOD = 1.89). Multipoint analyses showed two regions with some evidence for linkage to retinopathy: chromosome 3 between D3S3053 and D3S2427 (LOD = 1.36), and chromosome 9 between D9S1120 and D9S910 (LOD = 1.46). These linkage analyses suggest that a genetic element on chromosome 7 and possibly one on chromosome 20 influence susceptibility to diabetic nephropathy but not retinopathy. Genetic elements on chromosome 3 and 9 may determine susceptibility to both these complications. These loci could presumably influence susceptibility to the complications by influencing the microvasculature directly, by influencing the severity of hyperglycemia, or by other unknown mechanisms.

The relationship of menstrual irregularity to type 2 diabetes in Pima Indian women

OBJECTIVE

Menstrual irregularity is associated with hyperinsulinemia and hyperandrogenemia in nondiabetic Pima Indian women of child-bearing age. In this population-based study, we determined the relationship of menstrual irregularity to type 2 diabetes in Pima Indian women.

RESEARCH DESIGN AND METHODS

Participants for this cross-sectional analysis were 695 nonpregnant Pima Indian women, aged 18-44 years, involved in an ongoing epidemiologic study of diabetes among residents of the Gila River Indian Community of Arizona. Clinical data were collected by questionnaire and an examination that included a 75-g oral glucose tolerance test; diabetes was diagnosed by World Health Organization criteria. Menstrual irregularity was defined as an interval of 3 months or more between menses, when not pregnant, since age 18 years.

RESULTS

History of menstrual irregularity was significantly associated with a high prevalence of diabetes (37 vs. 13%; odds ratio = 4.2, 95% CI = 1.6-10.8) in the least obese women (BMI < 30 kg/m2), adjusted for the effects of age and overall obesity. This association was, in part, because of greater central obesity in women with irregular menses. In more obese women, there was little association with menstrual irregularity, and diabetes was frequent regardless of menstrual history.

CONCLUSIONS

Prevalence of type 2 diabetes is higher among Pima indian women with a history of menstrual irregularity. The difference is most pronounced among the least obese group of women. This association may be because of insulin resistance and hyperinsulinemia, which predict type 2 diabetes, also causing hyperandrogenism and menstrual irregularity. The findings reinforce the need to evaluate women with menstrual irregularity for hyperglycemia.

Dietary calcium and blood pressure in a Native American population

OBJECTIVE

To assess the relationship between dietary calcium and blood pressure.

METHODS

Cross-sectional study of 404 adult Pima Indians of Arizona. Dietary variables were assessed by the 24-hour recall. Hypertension (HTN) was defined as systolic blood pressure (SBP) > or = mmHg or diastolic blood pressure (DBP) > or = 90 mmHg or drug treatment.

RESULTS

Controlled for age and sex, dietary calcium intake was higher in subjects with HTN than in those without (p < 0.01), and higher dietary calcium was associated with a higher prevalence of HTN (odds ratio comparing highest with lowest tertile group of calcium = 2.6, 95% CI 1.4-4.8). Age-sex-adjusted men DBP in low, middle and high tertiles of calcium was 74, 76, and 79 mmHg, respectively (p < 0.001). SBP was not significantly different in the three tertiles (p = 0.07). Multiple regression analyses that controlled for age, sex, body mass index, sodium, potassium and alcohol also suggested a positive association between DBP and dietary calcium (p < 0.01), an association which was stronger at higher glucose concentrations (p < 0.01 for the calcium-glucose interaction).

CONCLUSION

In Pima Indians, a population with a high incidence of diabetes, the inverse association between dietary calcium and blood pressure reported in other populations was not found.

Non-insulin dependent diabetes mellitus and alveolar bone loss progression over 2 years

This study tested the hypothesis that persons with non-insulin dependent diabetes mellitus (NIDDM) have greater risk of more severe alveolar bone loss progression over a 2-year period than those without NIDDM. Data from the longitudinal study of the oral health of residents of the Gila River Indian Community were analyzed for 362 subjects, aged 15 to 57, 338 of whom had less than 25% radiographic bone loss at baseline, and who did not develop NIDDM nor lose any teeth during the 2-year study period. The other 24 subjects had NIDDM at baseline, but met the other selection criteria. Bone scores (scale 0-4) from panoramic radiographs corresponded to bone loss of 0%, 1%-24%, 25%-49%, 50%-74%, or 75% and greater. Change in bone score category was computed as the change in worst bone score (WBS) reading after 2 years. Age, calculus, NIDDM status, time to follow-up examination, and baseline WBS were explanatory variables in regression models for ordinal categorical response variables. NIDDM was positively associated with the probability of a change in bone score when the covariates were controlled. The cumulative odds ratio for NIDDM at each threshold of the ordered response was 4.23 (95% C.I. = 1.80, 9.92). In addition to being associated with the incidence of alveolar bone loss (as demonstrated in previous studies), these results suggest an NIDDM-associated increased rate of alveolar bone loss progression.

Randomized clinical trial of lifestyle interventions in Pima Indians: a pilot study

A pilot trial was conducted to test adherence to specific lifestyle interventions among Pima Indians of Arizona, and to compare them for changes in risk factors for diabetes mellitus. Ninety-five obese, normoglycaemic men and women, aged 25-54 years, were randomized to treatments named 'Pima Action' (Action) and 'Pima Pride' (Pride), which were tested for 12 months. Action involved structured activity and nutrition interventions, and Pride included unstructured activities emphasizing Pima history and culture. Adherence to interventions, changes in self-reported activity and diet, and changes in weight, glucose concentrations, and other risk factors were assessed regularly. Thirty-five eligible subjects who had declined randomization were also followed as an 'observational' group and 22 members of this group were examined once at a median of 25 months for changes in weight and glucose concentration. After 12 months of intervention, members of both intervention groups reported increased levels of physical activity (median: Action 7.3 h month(-1), Pride 6.3 h month(-1), p < 0.001 for each), and Pride members reported decreased starch intake (28 g, p = 0.008). Body mass index, systolic and diastolic blood pressures, weight, 2-h glucose and 2-h insulin had all increased in Action members (p < 0.003 for each), and waist circumference had decreased in Pride members (p = 0.05). Action members gained more weight than Pride members (2.5 kg vs 0.8 kg, p = 0.06), and had a greater increase in 2-h glucose than Pride members (1.33 mM vs 0.03 mM, p = 0.007). Members of the observational group gained an average of 1.9 kg year(-1) in weight and had an increase of 0.36 mM year(-1) in 2-h glucose. Sustaining adherence in behavioural interventions over a long term was challenging. Pimas may find a less direct, less structured, and more participative intervention more acceptable than a direct and highly structured approach.

Serum cholesterol and mortality rates in a Native American population with low cholesterol concentrations: a U-shaped association

BACKGROUND

Low serum cholesterol concentrations are associated with high death rates from cancer, trauma, and infectious diseases, but the meaning of these associations remains controversial. The present report evaluates whether low cholesterol is likely to be a causal factor for mortality from all causes or from specific causes.

METHODS AND RESULTS

Among 4553 Pima Indians > or =20 years old, a population with low serum cholesterol (median, 4.50 mmol/L), 1077 deaths occurred during a mean follow-up of 12.8 years. Trauma was the most common cause. The relationship between serum cholesterol measured at 2-year intervals and age- and sex-standardized mortality rates was U-shaped. Cholesterol was related positively to mortality from cardiovascular diseases and diabetes (including nephropathy) and negatively to mortality from cancer and alcohol-related diseases. The relationship was U-shaped for mortality from infectious diseases, and cholesterol was not related to mortality from trauma. Change in cholesterol from one examination to the next was positively related to mortality from diabetes. In proportional-hazards models adjusted for potential confounders, the relationship between baseline cholesterol and mortality was U-shaped for all causes and diabetes and positive for cardiovascular diseases. Other relationships were nonsignificant. Among 3358 subjects followed > or =5 years, the relationship was significant and positive only for mortality from cardiovascular diseases.

CONCLUSIONS

Despite a high exposure risk for Pima Indians, if low cholesterol level is a causal factor, the relationships between low serum cholesterol and high mortality rates probably result from diseases lowering cholesterol rather than from a low cholesterol causing the diseases.

Parity, postmenopausal estrogen use, and cardiovascular disease risk factors in American Indian women: the Strong Heart Study

Studies have suggested that high parity is related to an increased risk of cardiovascular disease (CVD). Reasons for an increased risk are unclear but may include influences of child-bearing on levels of CVD risk factors. The present study examined the associations of parity and CVD risk factors in American Indian women, among whom large families are common. Estrogen use and CVD risk factors also were assessed. The study included 1982 ever-married, postmenopausal women aged 45 through 74 years who participated in the Strong Heart Study (SHS), a large study of American Indians in three geographic areas of the United States. Information was obtained during a physical examination and interview. Parity ranged from 0 to 18 (median 5). Current estrogen use varied from 5% in Arizona to 21% in Oklahoma. Multivariable analyses found a statistically significant, inverse association between parity and high-density lipoprotein (HDL) cholesterol, although the difference with increasing parity was small (-0.26 mg/dl per additional live birth). Estrogen users had significantly lower levels of low-density lipoprotein cholesterol (-6.4 mg/dl) and fibrinogen (-26.2 mg/dl) and a lower waist/hip ratio (-0.02), and higher values of HDL (5 mg/dl) and logarithm (ln) triglyceride (0.13 mg/dl). Current users were slightly more likely to be hypertensive (prevalence odds ratio, 1.56). Relations between parity and CVD risk factors in American Indian women with high parity suggested only small differences with increasing parity. Associations with estrogen use are much stronger and are similar to those observed in other groups of women.

Fasting hyperinsulinemia is a predictor of increased body weight gain and obesity in Pima Indian children

Hyperinsulinemia is commonly associated with obesity, but it has not been determined which defect comes first. Some have proposed that hyperinsulinemia may precede obesity in populations prone to NIDDM, such as Pima Indians or Pacific Islanders. In contrast, longitudinal studies in adults show that insulin sensitivity and low fasting insulin concentrations are associated with increased weight gain, whereas insulin resistance seems to protect against weight gain. The present study examined whether fasting plasma hyperinsulinemia is a risk factor for weight gain in prepubertal children in the Pima Indian population-a population that is prone to obesity. Fasting plasma insulin concentration was measured in 328 5- to 9-year-old Pima Indian children (147 boys and 181 girls) with normal glucose tolerance. Follow-up weight was obtained an average of 9.3 +/- 1.9 years (means +/- SD) later at age 15-19 years. Fasting plasma insulin concentration correlated with the rate of weight gain per year in both boys (r = 0.42; P < 0.0001) and girls (r = 0.20; P < 0.01) and was associated with the rate of weight gain, independent of known determinants of weight change, i.e., initial relative weight, change in height, age, and sex. Similar relationships were found between fasting plasma insulin concentration and the change in relative weight and in triceps skinfold thickness-two indicators of obesity. In conclusion, fasting hyperinsulinemia may be a risk factor for the development of obesity in young children.

Breastfeeding and incidence of non-insulin-dependent diabetes mellitus in Pima Indians

BACKGROUND

Early exposure to cow's milk has been implicated in the occurrence of insulin-dependent diabetes mellitus but there is little information about infant-feeding practices and subsequent non-insulin-dependent diabetes mellitus (NIDDM). We examined the association between breastfeeding and NIDDM in a population with a high prevalence of this disorder, the Pima Indians.

METHODS

Glucose-tolerance status was obtained from a 75 g oral glucose-tolerance test. A standard questionnaire given to mothers was used to classify infant-feeding practices for the first 2 months of life into three groups; exclusively breastfed, some breastfeeding, or exclusively bottlefed. The association between the three infant-feeding groups and NIDDM was analysed by multiple logistic regression.

FINDINGS

Data were available for 720 Pima Indians aged between 10 and 39 years. 325 people who were exclusively bottlefed had significantly higher age-adjusted and sex-adjusted mean relative weights (146%) than 144 people who were exclusively breastfed (140%) or 251 people who had some breastfeeding (139%) (p = 0.019). People who were exclusively breastfed had significantly lower rates of NIDDM than those who were exclusively bottlefed in all age-groups (age 10-19, 0 of 56 vs 6 [3.6%] of 165; age 20-29, 5 [8.6%] of 58 vs 17 [14.7%] of 116]; age 30-39, 6 [20.0%] of 30 vs 13 [29.6%] of 44). The odds ratio for NIDDM in exclusively breastfed people, compared with those exclusively bottlefed, was 0.41 (95% CI 0.18-0.93) adjusted for age, sex, birthdate, parental diabetes, and birthweight.

INTERPRETATION

Exclusive breastfeeding for the first 2 months of life is associated with a significantly lower rate of NIDDM in Pima indians. The increase in prevalence of diabetes in some populations may be due to the concomitant decrease in breastfeeding.

Diabetic retinopathy assessed by fundus photography in Pima Indians with impaired glucose tolerance and NIDDM

In a population-based epidemiological study, 991 Pima Indians with non-insulin-dependent (Type 2) diabetes mellitus (NIDDM) and 288 without diabetes aged > or =15 years were examined for retinopathy by fundus photography with a 45 degrees fundus camera after mydriasis. The photographs were graded using a modified Airlie-House classification scheme. The associations of several factors with retinopathy were studied by logistic regression. Non-proliferative retinopathy was present in 11.2 % (19/169) subjects at the time of diagnosis of diabetes and in 8.3% (4/48) in newly diagnosed subjects who had a documented non-diabetic oral glucose tolerance test within 4 years prior to diagnosis of diabetes. The prevalence of retinopathy in subjects with impaired glucose tolerance was 12% (8/68). Retinopathy at the time of diagnosis of diabetes was significantly associated with lower body mass index and higher systolic blood pressure but not glycaemia. Retinopathy was present in 375 (37.8 %) diabetic subjects and 14 (5.2 %) non-diabetic subjects. Among all subjects with diabetes (duration 0-37 years), stepwise multivariate analysis showed non-proliferative retinopathy to be associated with duration of diabetes, mean blood pressure, fasting plasma glucose, treatment with insulin and albuminuria. Proliferative retinopathy was seen in 34 (2.7%) of diabetic and none of the non-diabetic subjects, and was associated with 2 h post-load glucose concentrations, as well as albuminuria, insulin treatment, younger age, and diastolic blood pressure. These data confirm the need for fundus examination at the time of diagnosis of diabetes and during long-term follow-up. Albuminuria and blood pressure are potentially modifiable risk factors and the impact of treating these on incidence and progression of diabetic retinopathy need to be assessed.

Predictors of progression from impaired glucose tolerance to NIDDM: an analysis of six prospective studies

Risk factors associated with the progression from impaired glucose tolerance (IGT) to NIDDM were examined in data from six prospective studies. IGT and NIDDM were defined in all studies by World Health Organization (WHO) criteria, and baseline risk factors were measured at the time of first recognition of IGT. The studies varied in size from 177 to 693 participants with IGT, and included men and women followed from 2 to 27 years after the recognition of IGT. Across the six studies, the incidence rate of NIDDM was 57.2/1,000 person-years and ranged from 35.8/1,000 to 87.3/1,000 person-years. Although baseline measures of fasting and 2-h postchallenge glucose levels were both positively associated with NIDDM incidence, incidence rates were sharply higher for those in the top quartile of fasting plasma glucose levels, but increased linearly with increasing 2-h postchallenge glucose quartiles. Incidence rates were higher among the Hispanic, Mexican-American, Pima, and Nauruan populations than among Caucasians. The effect of baseline age on NIDDM incidence rates differed among the studies; the rates did not increase or rose only slightly with increasing baseline age in three of the studies and formed an inverted U in three studies. In all studies, estimates of obesity (including BMI, waist-to-hip ratio, and waist circumference) were positively associated with NIDDM incidence. BMI was associated with NIDDM incidence independently of fasting and 2-h post challenge glucose levels in the combined analysis of all six studies and in three cohorts separately, but not in the three studies with the highest NIDDM incidence rates. Sex and family history of diabetes were generally not related to NIDDM progression. This analysis indicates that persons with IGT are at high risk and that further refinement of risk can be made by other simple measurements. The ability to identify persons at high risk of NIDDM should facilitate clinical trials in diabetes prevention.

Diagnosing diabetes mellitus--do we need new criteria?

The current classification and diagnostic criteria for diabetes mellitus were introduced by the United States National Data Group in 1979 and endorsed by the World Health Organization in 1980, with modifications in 1985 and 1994. The criteria, chosen to reflect the risk of complications, were the synthesis of considerable thought and expertise and represented a consensus which, it was hoped, would prove helpful to all those involved with diabetes-practising clinician, research scientist and epidemiologist alike. The inconvenience, variability and non-physiological nature of the oral glucose tolerance test (OGTT) are well-recognised. In spite of these limitations the 2-h post-load plasma glucose has remained the standard against which all other tests have been evaluated. This article reviews the original justification for the OGTT, and in the light of more recent epidemiological research seeks to place the current diagnostic criteria for diabetes into a pathophysiological, diagnostic and prognostic perspective.

Plasma lipoproteins and incidence of non-insulin-dependent diabetes mellitus in Pima Indians: protective effect of HDL cholesterol in women

The role of plasma lipoproteins in the development of non-insulin-dependent diabetes mellitus (NIDDM) was studied in 787 non-diabetic (2-h glucose < 11.1 mmol/l) Pima Indians (265 men and 522 women). Subjects were followed for a mean of 9.8 (range: 1.8-16.4) years, during which 261 (76 men and 185 women) developed NIDDM. In men and women, very-low-density lipoprotein (VLDL) cholesterol, VLDL triglyceride, low-density lipoprotein triglyceride and total triglyceride, controlled for age, predicted NIDDM (P < 0.01 for each). These effects diminished when controlled for age, sex, body mass index, systolic blood pressure and 2-h glucose. However, high-density lipoprotein (HDL) cholesterol, controlled for age, body mass index, systolic blood pressure and 2-h glucose, was a significant protective factor for NIDDM in women (hazard rate ratio (HRR) = 0.35, 95% CI (0.23-0.54), P < 0.001, 90th compared with 10th percentile) but not in men (HRR = 1.04, 95% CI (0.53-2.05), P = 0.915). This association remained significant in women when controlled for fasting or 2-h plasma insulin concentrations, other estimates of insulin resistance or alcohol consumption. The protective effect of HDL cholesterol was similar among women with normal (2-h glucose < 7.8 mmol/1) or impaired (7.8 mmol/l < or = 2-h glucose < 11.1 mmol/l) glucose tolerance at baseline. These results indicate that lipoprotein disorders are an early accompaniment of the abnormalities that lead to NIDDM.

Survival during renal replacement therapy for diabetic end-stage renal disease in Pima Indians

OBJECTIVE

To examine survival in Pima Indians receiving renal replacement therapy for end-stage renal disease attributed to NIDDM.

RESEARCH DESIGN AND METHODS

Vital status through 1994 was determined for 136 diabetic Pima Indians from the Gila River Indian Community who began renal replacement therapy between 1973 and 1990.

RESULTS

Median survival from the onset of renal replacement therapy was 39 months (95% Ci, 31-54), 31 months (95% Ci, 11-48) in those who began treatment between 1973 and 1981, and 44 months (95% Ci, 32-56) in those who began treatment between 1982 and 1990 (P = 0.020). During these periods, mean age at onset of treatment increased from 53.3 to 56.1 years (P = 0.166), and mean duration of diabetes at the onset of treatment increased from 16.5 to 20.2 years (P = 0.003). After adjustment for sex, duration of diabetes, initial dialysis type, and kidney transplantation by an age-stratified proportional-hazards analysis, the death rate after starting renal replacement therapy in the second half of the study was 0.54 times (95% CI, 0.33-0.88) that in the first half. If this analysis was restricted to those who survived at least 90 days of therapy, the difference between the time periods was diminished (death rate ratio = 0.76; 95% CI, 0.43-1.32).

CONCLUSIONS

Survival in Pima Indians receiving renal replacement therapy improved significantly over the study despite an increase in the average age and diabetes duration of those beginning dialysis. Much of the improvement in survival is attributable to a reduction in the number of deaths within the first 90 days of therapy. The median survival of 47 months in Pima Indians < 65 years old at the initiation of therapy is substantially longer than the 30 months reported in blacks and 16 months reported in whites of similar age with NIDDM.

Incidence of diabetes mellitus in women following impaired glucose tolerance in pregnancy is lower than following impaired glucose tolerance in the non-pregnant state

Impaired glucose tolerance (IGT), which is asymptomatic and requires a glucose tolerance test for detection, is a well-known risk factor for diabetes mellitus. Outside the research setting it is rarely identified in people who lack specific risk factors for diabetes except during pregnancy, at which time screening with an oral glucose challenge is a routine procedure. A 75-g oral glucose tolerance test was performed during the latter part of pregnancy or during a routine epidemiology survey in 15-39-year-old Pima Indian women with no history of abnormal glucose tolerance. Those with IGT by World Health Organization criteria were included in this study. Diabetes incidence in women was compared between those whose IGT was first detected during pregnancy and those who were not pregnant when IGT was first recognized. Seventeen of 73 pregnant women and 114 of 244 non-pregnant women developed diabetes within 10 years. When controlled for plasma glucose concentration, age, body mass index, parity and duration of follow-up, those who were not pregnant were at higher risk of developing diabetes than those who were pregnant (hazard rate ratio = 1.71, 95% confidence interval = 1.01-2.91). Previous studies had reported that women with IGT during pregnancy are at higher risk of diabetes than women with normal glucose tolerance. This study suggests that women with IGT during pregnancy are at lower risk than non-pregnant women with a similar plasma glucose concentration who, in the clinical setting, are likely to remain unrecognized.

Dual energy X-ray absorptiometry: inter-machine variability

OBJECTIVE

Dual-energy X-ray absorptiometry (DEXA) is rapidly becoming the method of choice for body composition measurements. We tested inter-machine variability because large differences in body composition measurements between different DEXA machines have recently been reported.

DESIGN

Comparison of total body scans using 2 DEXA machines from the same manufacturer (DPX-L; Lunar Co, Madison, WI) on 10 volunteers (5M/5F).

RESULTS

We observed statistically significant differences between the 2 machines for all mean values of body composition variables as a result of a systematic underestimation of bone mineral and overestimation of fat tissue by one machine vs the other. However, the magnitude of the observed differences was small (namely bone mineral +68 +/- 57 g; percent body fat -1.7 +/- 1%, Mean +/- s.d.).

CONCLUSION

Differences do exist in the performances of 2 DEXA machines from the same manufacturer. Although the differences reported in the present study are small, emphasis should be given in pre-testing machines when multiple apparatuses are used in a study. Also, because the observed error was systematic, randomized designs are necessary when more than one DEXA machine is used in longitudinal/intervention study. Better yet, manufacturers of DEXA machine should standardize their equipment to ensure the best consistency between machines.

Severe periodontitis and risk for poor glycemic control in patients with non-insulin-dependent diabetes mellitus

This study tested the hypothesis that severe periodontitis in persons with non-insulin-dependent diabetes mellitus (NIDDM) increases the risk of poor glycemic control. Data from the longitudinal study of residents of the Gila River Indian Community were analyzed for dentate subjects aged 18 to 67, comprising all those: 1) diagnosed at baseline with NIDDM (at least 200 mg/dL plasma glucose after a 2-hour oral glucose tolerance test); 2) with baseline glycosylated hemoglobin (HbA1) less than 9%; and 3) who remained dentate during the 2-year follow-up period. Medical and dental examinations were conducted at 2-year intervals. Severe periodontitis was specified two ways for separate analyses: 1) as baseline periodontal attachment loss of 6 mm or more on at least one index tooth; and 2) baseline radiographic bone loss of 50% or more on at least one tooth. Clinical data for loss of periodontal attachment were available for 80 subjects who had at least one follow-up examination, 9 of whom had two follow-up examinations at 2-year intervals after baseline. Radiographic bone loss data were available for 88 subjects who had at least one follow-up examination, 17 of whom had two follow-up examinations. Poor glycemic control was specified as the presence of HbA, of 9% or more at follow-up. To increase the sample size, observations from baseline to second examination and from second to third examinations were combined. To control for non-independence of observations, generalized estimating equations (GEE) were used for regression modeling. Severe periodontitis at baseline was associated with increased risk of poor glycemic control at follow-up. Other statistically significant covariates in the GEE models were: 1) baseline age; 2) level of glycemic control at baseline; 3) having more severe NIDDM at baseline; 4) duration of NIDDM; and 5) smoking at baseline. These results support considering severe periodontitis as a risk factor for poor glycemic control and suggest that physicians treating patients with NIDDM should be alert to the signs of severe periodontitis in managing NIDDM.

A two-step strategy for identification of high-risk subjects for a clinical trial of prevention of NIDDM

OBJECTIVE

To evaluate 2-h plasma glucose (2HPG), fasting plasma glucose (FPG), glycosylated hemoglobin (HbA1), a combination of FPG and HbA1 (FPG-HbA1), and other factors as screening tests for identifying high-risk subjects for a clinical trial of prevention of NIDDM and to identify strategies to minimize the total number of oral glucose tolerance tests (OGTTs) required to recruit eligible subjects to the trial.

RESEARCH DESIGN AND METHODS

One thousand, one hundred and eight nondiabetic Pima Indians aged 25-64 years were followed for up to 5 years, and factors predicting NIDDM, defined by World Health Organization criteria (2HPG > or = 11.1 mmol/l), were assessed using Cox's proportional hazards analysis. Various threshold values of FPG, HbA1, and FPG-HbA1 were determined, which, when combined with an OGTT, identified subjects with impaired glucose tolerance (IGT) (2HPG > or = 7.8 and < 11.1 mmol/l) at a number of specified risks for developing NIDDM in 5 years. The value of each of the three tests was then assessed by calculating (for each threshold) the numbers to be screened, the numbers requiring an OGTT, and the sample size of IGT subjects needed to detect a 33% reduction in NIDDM by an experimental intervention at a power of 80%.

RESULTS

During a median of 4.3 years of follow-up, 91 (8.2%) of the 1.108 nondiabetic subjects developed NIDDM. The estimated 5-year cumulative incidence rate was 13.5%. Each of the variables, 2HPG, FPG, HbA1, FPG-HbA1, BMI, IGT, and systolic (sBP), diastolic (dBP), and mean (MBP) blood pressures, predicted NIDDM (P < 0.05 for each) when controlled for age and sex. In a stepwise proportional hazards analysis model, 2HPG and FPG-HbA1 (P < 0.001 for each) were selected as the best set of predictors of NIDDM and of fasting hyperglycemia (FPG > or = 7.8 mmol/l).

CONCLUSIONS

A two-step strategy, in which high-risk individuals are first identified by FPG or FPG-HbA1 and then the OGTT is used to select subjects with IGT, requires fewer OGTTs than when using 2HPG as the initial screening test without substantially increasing the numbers that would need to be screened. Such a strategy also offers the advantage of reducing the necessary sample size and is therefore an effective, efficient, and convenient method of identifying eligible subjects for a clinical trial of prevention of NIDDM.

Familial aggregation of medial arterial calcification in Pima Indians with and without diabetes

OBJECTIVE

Little is known about medial arterial calcification (MAC) other than its association with age, sex, diabetes, and diabetes complications. Familial aggregation of this disorder was studied to determine the importance of potential genetic factors and to assess whether such familial aggregation was independent of that of diabetes.

RESEARCH DESIGN AND METHODS

Members of 1,256 Pima Indian nuclear families with 3,339 offspring were examined radiologically for MAC of the feet. Multiple logistic regression analyses were used to compare the presence of the disorder in a parent with the presence of MAC in an offspring and to determine whether familial aggregation of MAC was independent of parental diabetes.

RESULTS

Controlled for age, sex, diabetes, serum cholesterol, and blood pressure, offspring of one parent with MAC had 3.3 (95% CI 1.5-7.6) times the odds of MAC as did offspring of parents without MAC, and offspring with both parents affected had an even higher risk (odds ratio, 8.1; 95% CI 3.4-18.8). Controlled for offspring age and sex and for parental age and diabetes, parental MAC was associated with the disorder in offspring (P < 0.001), but the effect of parental diabetes on MAC in the offspring was not significant when controlled for parental MAC (P = 0.36). Furthermore, offspring of nondiabetic parents with MAC, controlled for age, sex, diabetes, and diabetes duration, had 1.7 (95% CI 0.9-3.1) times the odds of MAC than did offspring of diabetic parents with MAC.

CONCLUSIONS

Independent of parental age and diabetes and offspring age, sex, diabetes, and diabetes complications, parental MAC confers an increased risk of MAC in offspring. These findings suggest that the factors responsible for the familial clustering of MAC may be different from those for diabetes.

Weight fluctuation, mortality and vascular disease in Pima Indians

OBJECTIVE

To examine the relationship of weight fluctuation to mortality rates and incidence of vascular disease.

SUBJECTS

A cohort of Pima Indians, 572 of whom had non-insulin-dependent diabetes mellitus and 766 without diabetes.

DESIGN

Individuals were invited biennially to research examinations. The root mean square error (RMSE) of the linear trend of weight with time for the first four examinations after age 20 years was used as an index of weight fluctuation. Subjects were followed from the fourth examination until death or until 31 December 1991. The mortality rate ratio (MRR) and its 95% confidence interval (CI) for those with a high weight fluctuation index relative to those with a lower value were determined. The median duration of follow up was 9.3 (range 0.1-22.6) years.

MEASUREMENTS

All cause mortality (n = 356); incidence of diabetic retinopathy (n = 145), diabetic nephropathy (n = 132) and electrocardiographic abnormalities (n = 82).

RESULTS

There was no significant relationship between weight fluctuation and mortality for diabetic subjects (MRR = 1.0, 95% CI 0.8-1.3, p = 0.91). Nondiabetic subjects with a high weight fluctuation index had a higher mortality rate than those with a lower index (MRR = 1.5, 95% CI 1.0-2.1, p = 0.03); the association was stronger among men than among women. The excess mortality in the high weight fluctuation group was not due to cardiovascular diseases, but to noncardiovascular causes and the risk for alcohol-related death was particularly increased. Weight fluctuation was not associated with the incidence of diabetic retinopathy, nephropathy or electrocardiographic abnormalities.

CONCLUSIONS

A high weight fluctuation index was associated with higher mortality rates in nondiabetic, but not in diabetic, Pima Indians. The excess mortality is largely due to noncardiovascular causes of death and may reflect lifestyle factors associated with weight fluctuation, rather than its metabolic effects.

Low prevalences of chronic widespread pain and shoulder disorders among the Pima Indians

OBJECTIVE

To establish the prevalence of shoulder disease and chronic widespread pain in Pima Indians.

METHODS

Cross sectional analyses of data from 4230 subjects for shoulder disease and 105 subjects for chronic widespread pain participating in population surveys

RESULTS

The prevalence of shoulder disease was 4.4% (95% CI, 3.8-5.1), age-sex adjusted to the 1980 US census population. This is lower than in a study of Caucasians [prevalence ratio (PR) = 0.29, 95% CI, 0.20-0.42 for men and PR = 0.55, 95% CI, 0.41-0.73 for women]. Shoulder disease was associated with non-insulin-dependent diabetes mellitus (PR = 1.67, 95% CI, 1.19-2.36). No chronic widespread pain was identified (95% CI, 0-3.5%).

CONCLUSION

Prevalence of these pain syndromes in Pima Indians is lower than in predominantly Caucasian populations. These findings suggest that these populations have different pain perception or different patterns of risk factors for these disorders.