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Biomedical subjects

S M Haffner

Publications and source records attributed to S M Haffner.

At least 235 records · Page 13Linked to original sources
PubMed1992

Excess androgenicity only partially explains the relationship between obesity and bone density in premenopausal women.

Obese subjects have increased bone density relative to non-obese subjects yet this relationship is not fully understood. We examined whether alterations in sex hormones or binding proteins might explain the effect of obesity on osteoporosis in 83 premenopausal women from the San Antonio Heart Study, a population-based study of diabetes. We measured total testosterone, oestradiol, oestrone, sex hormone binding globulin (SHBG), and serum dehydroepiandrosterone sulphate (DHEA-SO4). Bone density was assessed by a Hologic dual photon absorptometer. Lumbar spine and femoral neck density were positively correlated with body mass index (BMI). In addition, femoral neck density was positively correlated with DHEA-SO4. BMI was negatively correlated with SHBG. After adjustment for sex hormones by multiple linear regression a positive association between bone density and obesity still exists suggesting that the association between obesity and bone density is at least partially independent of sex steroids in premenopausal women.

Adult↗
PubMed1991

Hyperinsulinaemia: the key feature of a cardiovascular and metabolic syndrome.

In a population-based survey of 2,930 subjects, prevalence rates for obesity, Type 2 (non-insulin-dependent) diabetes mellitus, impaired glucose tolerance, hypertension, hypertriglyceridaemia, and hypercholesterolaemia were 54.3, 9.3, 11.1, 9.8, 10.3 and 9.2%, respectively. The prevalence, however, of each of these conditions in its isolated form (free of the other five) was 29.0% for obesity, 1.3% for Type 2 diabetes, 1.8% for impaired glucose tolerance, 1.5% for hypertension, 1.0% for hypertriglyceridaemia, and 1.7% for hypercholesterolaemia. Two-by-two associations were even rarer. The large differences in prevalence between isolated and mixed forms indicate a major overlap among the six disorders in multiple combinations. In the isolated form, each condition was characterized by hyperinsulinaemia (both fasting and 2 h after oral glucose), suggesting the presence of insulin resistance. In addition, in any isolated condition most of the variables categorising other members of the sextet were still significantly altered in comparison with 1,049 normal subjects. In the whole of the subjects who presented with one or another disorder (1,881 of 2,930 or 64%), marked fasting and post-glucose hyperinsulinaemia was associated with higher body mass index, waist:hip ratio, fasting and post-glucose glycaemia, systolic and diastolic blood pressure, serum triglycerides and total cholesterol levels, and with lower HDL-cholesterol concentrations (all p less than 0.001). We conclude that (1) insulin sensitivity, glucose tolerance, blood pressure, body fat mass and distribution, and serum lipids are a network of mutually interrelated functions; and (2) an insulin resistance syndrome underlies each and all of the six disorders carrying an increased risk of coronary artery disease.

Adult↗
PubMed1991

High prevalence of angina pectoris in Mexican-American men. A population with reduced risk of myocardial infarction.

Mexican-American men experience lower rates of cardiovascular mortality and have a lower prevalence of nonfatal myocardial infarction than do non-Hispanic white men. To see if this ethnic difference exists for other cardiovascular end points, we compared the prevalence of angina pectoris, as assessed by the Rose Angina Questionnaire, between Mexican Americans (n = 3272) and non-Hispanic whites (n = 1848) examined in the San Antonio Heart Study, a population-based survey of cardiovascular disease and diabetes conducted in San Antonio, Texas, between 1979 and 1988. Contrary to our expectations, angina prevalence was approximately twice as high in Mexican Americans as in non-Hispanic whites, with age-adjusted odds ratios of 2.01 (95% confidence interval (CI), 1.13 to 3.58; P = .02) in men and 1.84 (95% CI, 1.26 to 2.70; P = .001) in women. After controlling for age, body mass index, diabetes status, cigarette smoking, and educational level by logistic regression analysis, angina prevalence remained statistically associated with Mexican American ethnicity in men, but not women. There was little ethnic difference in the proportion of Mexican-American and non-Hispanic white subjects who reported nonspecific chest pain (chest pain not meeting the Rose criteria), suggesting that the ethnic difference in angina prevalence was not an artifact of reporting bias. This was further supported by the fact that the conventional cardiovascular risk factors were more strongly associated with angina prevalence in Mexican Americans than in non-Hispanic whites. These data suggest that Mexican-American men experience high rates of angina despite low rates of myocardial infarction. Future studies should investigate ethnic factors that may have differential effects on the various manifestations of coronary heart disease.

Adult↗
PubMed1991

Greater influence of central distribution of adipose tissue on incidence of non-insulin-dependent diabetes in women than men.

Many studies have shown an increased prevalence of non-insulin-dependent diabetes (NIDDM) in individuals with an unfavorable body fat distribution, but there are still relatively few prospective studies on this topic. We present data on the 8-y incidence of NIDDM in Mexican-American men and women according to their degree of central adiposity, measured by the ratio of subscapular to triceps skinfold thicknesses. Subjects were initially enrolled in the San Antonio Heart Study, a population-based study of diabetes in Mexican Americans and non-Hispanic whites. Sixteen of 254 initially nondiabetic men and 27 of 366 initially nondiabetic women developed diabetes. Central adiposity was more strongly associated with diabetes incidence in women than in men. After adjustment for overall adiposity (measured by body mass index), women in the highest and in the middle tertile of centrality had a significantly higher risk of diabetes than did women in the lowest tertile [odds ratio (OR) = 10.70, P = 0.008, highest vs lowest tertile, and OR = 8.55, P = 0.032, middle vs lowest tertile; for men OR = 3.70 and OR = 1.38, respectively].

Adipose Tissue↗
PubMed1991

Obesity in Mexican American subgroups: findings from the San Antonio Heart Study.

This study describes the prevalence of overweight in 2013 Mexican Americans and 928 non-Hispanic whites, aged 25-65 y, who participated in phase 2 of the San Antonio Heart Study, 1984-1988, and examines differences in overall obesity and body fat distribution among diverse Mexican American subgroups defined by neighborhood, socioeconomic status (SES), and assimilation to mainstream US society. Prevalence of overweight was greater in Mexican Americans than in non-Hispanic whites, and the ethnic difference was greater in women than in men. In Mexican Americans the effects of SES and assimilation on overall obesity and body fat distribution differed by sex group. In men SES and cultural assimilation were associated with less favorable body fat distribution. In women SES and assimilation were associated with lower overall obesity and more favorable body fat distribution. Interventions to reduce obesity in Mexican Americans should take these subgroup differences into account.

Acculturation↗
PubMed1991

Predictors of obesity in Mexican Americans.

Excess body weight is a risk factor for morbidity and mortality in several studies. The etiology of obesity is, however, poorly understood. We examined the ability of selected behavioral variables to predict weight gain (greater than 6.8 kg) in the San Antonio Heart Study, a population-based study of diabetes and cardiovascular disease in Mexican Americans and non-Hispanic whites. However, we were unable to confirm an effect of dietary variables or level of physical exercise in predicting future obesity in Mexican Americans. To some degree this may be because of the imprecision of the 24-h-dietary-recall technique and the dietary behavior and exercise questionnaires.

Body Mass Index↗
PubMed1991

High blood pressure and insulin resistance: influence of ethnic background.

Hyperinsulinaemia links non-insulin dependent diabetes (NIDDM), obesity, and hypertension, each an insulin-resistant state in its own right. Insulin resistance predicts the occurrence of NIDDM, and plays a major role in its pathogenesis. We tested the hypothesis that hyperinsulinaemia may also predict hypertension in a sample (n = 2905) of the mixed population of San Antonio, in which hyperinsulinaemia and NIDDM are more prevalent among Mexican-Americans than non-Hispanic whites. Whilst in the whole sample the hypertensives had significantly (P less than 0.001) higher plasma insulin concentrations than the normotensives, high blood pressure was significantly (P less than 0.01) more frequent among non-Hispanic whites than Mexican-Americans regardless of diabetes status. After adjusting for factors (age, sex, body mass, and body fat distribution) known to affect insulin levels, a direct relationship between post-glucose plasma insulin concentrations and prevalence of hypertension was still present in both ethnic groups. In Mexican-Americans, however, the standardized prevalence of hypertension was significantly (P less than 0.001) lower at any given insulin concentration. Post-glucose plasma glucose levels also were directly related to hypertension prevalence in both groups; again, the regression line was shifted downward and, furthermore, less steep (P less than 0.02) in Mexican-Americans, suggesting relative protection against the negative effect of hyperglycaemia on blood pressure. Dyslipidaemia (higher total cholesterol and triglyceride, and lower HDL-cholesterol concentrations) was strongly associated with hyperinsulinaemia and blood pressure in both ethnic groups. After adjusting for plasma insulin, only hypertriglyceridaemia was associated with high blood pressure, with no inter-ethnic difference.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

Myocardial infarction in Mexican-Americans and non-Hispanic whites. The San Antonio Heart Study.

Mexican-American men experience reduced cardiovascular mortality compared with non-Hispanic white men. There is no corresponding ethnic difference in cardiovascular mortality in women. The difference in men could result either from a lower incidence of cardiovascular disease or a lower case fatality rate among Mexican-Americans. Although the incidence of cardiovascular disease in Mexican-Americans is unknown, we have collected data on prevalence of myocardial infarction in 5,148 individuals examined in the San Antonio Heart Study, a population-based survey of cardiovascular disease conducted between 1979 and 1988 in Mexican-Americans and non-Hispanic whites aged 25-64 years. Myocardial infarction was assessed by Minnesota-coded electrocardiograms and by a self-reported history of a physician-diagnosed heart attack. For both end points, the age-adjusted prevalence of myocardial infarction was lower in Mexican-American men than in non-Hispanic white men. After adjustment for age and diabetes status (present/absent), the odds of a myocardial infarction, as defined by either criterion, was approximately one third lower in Mexican-American men than in non-Hispanic white men (p = 0.06). In women, the prevalence of both myocardial infarction end points was slightly higher in Mexican-Americans than in non-Hispanic whites, although neither of these differences was significant. Although the ethnic differences in prevalence in this study were not statistically significant, their pattern parallels the pattern in the mortality due to cardiovascular diseases. Therefore, the results support the hypothesis that the reduced cardiovascular mortality rate observed in Mexican-American men reflects a lower incidence of myocardial infarction rather than a reduced case fatality rate because the latter would result in a higher prevalence.

Adult↗
PubMed1991

Dyslipidemia in type II diabetes. Implications for therapeutic intervention.

Cardiovascular disease, and in particular ischemic heart disease, is the principal cause of morbidity, functional disability, and mortality in patients with non-insulin-dependent (type II) diabetes. The main risk factors for the macrovascular complications of diabetes are dyslipidemia, hypertension, and cigarette smoking. Although degree of hyperglycemia is a risk factor for microvascular complications, it is not a prominent risk factor for macrovascular complications. Nevertheless, there are theoretical reasons for believing that glycemic control could lower cardiovascular risk. For example, glycemic control may both improve clearance and suppress hepatic overproduction of very-low-density lipoprotein. Moreover, there is direct empirical evidence that improved glycemic control can favorably alter lipid profiles in type II diabetic patients. Despite this, the only clinical trial that has assessed cardiovascular mortality as an end point in diabetic subjects (i.e., the University Group Diabetes Program) failed to demonstrate a benefit of glycemic control. In this study, the insulin-variable group, which achieved sustained glycemic control relative to the placebo group, had essentially the same cardiovascular mortality as the latter group. All of the conventional lipid-lowering agents have been shown to produce favorable changes in lipid profiles in diabetic subjects. However, the optimum regimen remains to be defined. Metabolic differences between diabetic and nondiabetic subjects mean that the optimum lipid-lowering regimens for the two categories of patients may differ. For example, nicotinic acid, which is a powerful lipid-altering drug, may worsen glucose intolerance. The characteristic lipid abnormalities in type II diabetic subjects are hypertriglyceridemia and low high-density lipoprotein cholesterol, not hypercholesterolemia. Although the role of hypertriglyceridemia as a cardiovascular risk factor in the general population has been questioned, there is evidence that this lipid abnormality may play a stronger role in diabetic subjects. For all of the above reasons, there is an urgent need for large-scale clinical trials assessing cardiovascular end points and testing various strategies of improving lipid profiles in diabetic subjects, particularly given the fact that all of the current generation of lipid-lowering trials have systematically excluded diabetic patients.

Blood Glucose↗
PubMed1991

Increased incidence of type II diabetes mellitus in Mexican Americans.

OBJECTIVE: To determine whether Mexican Americans have an increased incidence of non-insulin-dependent (type II) diabetes mellitus relative to non-Hispanic whites. Currently, no study has reported on the incidence of this disorder in Mexican Americans. RESEARCH DESIGN AND METHODS: We determined the 8-yr incidence of type II diabetes in 617 Mexican Americans and 306 non-Hispanic whites who participated in the San Antonio Heart Study, a population-based study of diabetes and cardiovascular disease. Forty Mexican Americans (6.5%) and 6 non-Hispanic whites (2%) developed type II diabetes, as defined by World Health Organization criteria. The age-adjusted ethnic odds ratio (OR; Mexican Americans/non-Hispanic whites) for diabetes incidence was 8.13 (95% confidence interval [C1] 1.10-59.9) in men and 3.62 (95% CI 1.37-9.55) in women. We adjusted for age, sex, ethnicity, body mass index, and level of educational attainment with multiple logistic regression analyses. RESULTS: Mexican Americans continued to show a statistically significant increase in diabetes incidence (OR 2.72, 95% CI 1.02-7.28). Obesity and age were also positively related to diabetes incidence in this analysis (P less than 0.001). In addition, subjects with at least some college education had a lower incidence of diabetes than those with less than a high school education (OR 0.51, 95% CI 0.26-0.99). CONCLUSIONS: The incidence of type II diabetes in Mexican Americans is greater than in non-Hispanic whites, a difference that is not explained by ethnic differences in obesity, age, or level of educational attainment.

Adult↗
PubMed1991

Decrease of lipoprotein(a) with improved glycemic control in IDDM subjects.

OBJECTIVE: Recently, lipoprotein(a) [Lp(a)] has been identified as a major risk factor for coronary heart disease. There are few data available on the influence of metabolic control on plasma Lp(a) concentrations in subjects with insulin-dependent diabetes mellitus (IDDM), a group at high risk for coronary heart disease. RESEARCH DESIGN AND METHODS: We examined the effects of improved metabolic control on plasma lipid and lipoproteins and Lp(a) concentrations in 12 subjects before and after 21 days of tight metabolic control. RESULTS: Glycosylated hemoglobin declined from 8.4 to 6.9% (P less than 0.001), and Lp(a) declined from 29.7 to 27.1 mg/dl (P = 0.022). There were no significant differences in total, low-density lipoprotein, or high-density lipoprotein cholesterol, although the decline in triglyceride concentrations were borderline statistically significant. The distribution of apolipoprotein(a) isoforms in IDDM patients was not unusual, and the apolipoprotein(a) isoform phenotypes did not change with improved metabolic control. Lp(a) concentrations were also significantly higher than in a population-based control group of nondiabetic subjects from the San Antonio Heart Study. CONCLUSIONS: Although the number of subjects was small and the degree of improvement in metabolic control was modest, the results suggest that improved metabolic control may decrease the risk of coronary heart disease mediated by Lp(a) in IDDM.

Adult↗
PubMed1991

Genetic and environmental determinants of type II diabetes in Mexican Americans. Is there a "descending limb" to the modernization/diabetes relationship?

Evidence from migrant population studies and secular trend data indicates that environmental factors play a role in the etiology of non-insulin-dependent (type II) diabetes. These environmental factors appear to be concomitants of the process whereby traditional populations become "modernized" or "westernized" and include increased intake of total calories, fat, and sucrose, decreased intake of total and complex carbohydrates, including fiber, and decreased physical exercise. There also appears to be a "postmodernization" process, which we have characterized as the "descending limb of the curve." In Mexican Americans in San Antonio, the prevalence of type II diabetes declines with acculturation to the values, attitudes, and behaviors of "postmodernized" American society. However, examination of the dietary and exercise concomitants of this process revealed a mixed picture. There was some suggestion that Mexican-American women, although not men, had entered onto the descending limb of the curve. However, Native American genetic admixture in Mexican Americans also covaried with affluence and acculturation in such a way that the declining prevalence of diabetes could as easily be due to genetic factors as to environmental factors. The "pancreatic exhaustion" theory holds that resistance to insulin action is a principal lesion leading to hypersecretion of insulin, hyperinsulinemia, and eventual islet cell failure and clinical diabetes. This theory predicts that prediabetic subjects will be hyperinsulinemic. In conformity with this theory, we have shown that subgroups of the Mexican-American population, defined on the basis of family history of diabetes, who would be expected a priori to be enriched with prediabetic subjects, are hyperinsulinemic as predicted.(ABSTRACT TRUNCATED AT 250 WORDS)

Diabetes Mellitus↗
PubMed1991

Macrovascular complications in Mexican Americans with type II diabetes.

Mexican Americans have a threefold greater prevalence of non-insulin-dependent (type II) diabetes mellitus than non-Hispanic whites in the San Antonio Heart Study, a population-based study of diabetes. In addition, Mexican-American diabetic subjects (n = 365) have greater fasting glycemia than non-Hispanic white diabetic subjects (P less than 0.001). Despite these findings, and despite a higher prevalence of microvascular complications among Mexican Americans, there does not appear to be a marked difference in prevalence of macrovascular complications between Mexican-American and non-Hispanic white diabetic subjects. Mexican-American diabetic subjects have only a moderate excess of peripheral vascular disease (as judged by ankle-arm blood pressure ratios) relative to non-Hispanic white diabetic subjects (sex-adjusted Mantel-Haenszel odds ratio 1.84, 95% confidence interval 0.75-4.49). Mexican-American diabetic subjects actually reported fewer myocardial infarctions than non-Hispanic white diabetic subjects (sex-adjusted Mantel-Haenszel odds ratio 0.73, 95% confidence interval 0.31-1.71). Duration was not associated with either peripheral vascular disease or myocardial infarction. Severity of glycemia was only mildly associated with presence of peripheral vascular disease and negatively associated with self-reported myocardial infarction. This latter finding may represent a survival bias in that more severe diabetic subjects have already died and are not ascertained in a prevalence study. The absence of an ethnic difference in the prevalence of macrovascular disease contrasts with our previous reports from the San Antonio Heart Study, in which the prevalence of both retinopathy and proteinuria was observed to be higher in Mexican-American diabetic subjects.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

Increased upper body and overall adiposity is associated with decreased sex hormone binding globulin in postmenopausal women.

An unfavorable body fat distribution is associated with many metabolic abnormalities including a high prevalence and incidence of noninsulin dependent diabetes mellitus and decreased high density lipoprotein cholesterol and increased triglyceride levels. One mechanism for the effect of body fat distribution on metabolic variables may be through sex hormones. We examined the relationship of body mass index (BMI), ratio of subscapular-to-triceps skinfold ratio (centrality index) and ratio of waist-to-hip ratio (WHR) to sex hormone binding globulin (SHBG) (an in vivo measure of androgenicity) in 101 postmenopausal Mexican-American and non-Hispanic white women from the San Antonio Heart Study, a population based study of diabetes and cardiovascular disease. SHBG was significantly correlated with BMI (r = -0.440, P less than 0.001), WHR (r = -0.255, P less than 0.01) and centrality index (r = -0.210, P less than 0.05). In a multiple linear regression analysis, SHBG remained significantly associated with BMI (P less than 0.001) and WHR (P less than 0.05) but not with age, ethnicity or centrality index. This work suggests that in postmenopausal women overall adiposity and an unfavorable body fat distribution are associated with increased androgenicity as measured by a lower SHBG concentration. Our finding may help to explain the association of body fat distribution with diabetes and cardiovascular risk factors in older women.

Adipose Tissue↗
PubMed1990

Cardiovascular risk factors in confirmed prediabetic individuals. Does the clock for coronary heart disease start ticking before the onset of clinical diabetes?

Although type II diabetes is associated with both microvascular and macrovascular complications, duration of diabetes and severity of glycemia are strongly associated only with the former. Since prediabetic individuals are hyperinsulinemia, and since hyperinsulinemia may be a cardiovascular risk factor, we hypothesized that prediabetic individuals might have an atherogenic pattern of risk factors even before the onset of clinical diabetes, thereby explaining the relative lack of an association of macrovascular complications with either glycemic severity or disease duration. We documented the cardiovascular risk factor status of 614 initially nondiabetic Mexican Americans who later participated in an 8-year follow-up of the San Antonio Heart Study, a population-based study of diabetes and cardiovascular disease. Individuals who were nondiabetic at the time of baseline examination, but who subsequently developed type II diabetes (ie, confirmed prediabetic subjects, n = 43), had higher levels of total and low-density lipoprotein cholesterol, triglyceride, fasting glucose and insulin, 2-hour glucose, body mass index, and blood pressure, and lower levels of high-density lipoprotein cholesterol than subjects who remained nondiabetic (n = 571). Most of these differences persisted after adjustment for obesity and/or level of glycemia, but were abolished after adjustment for fasting insulin concentration. When subjects with impaired glucose tolerance at baseline (n = 106) were eliminated, the more atherogenic pattern of cardiovascular risk factors was still evident (and statistically significant) among initially normoglycemic prediabetic subjects. These results indicate that prediabetic subjects have an atherogenic pattern of risk factors (possibly caused by obesity, hyperglycemia, and especially hyperinsulinemia), which may be present for many years and may contribute to the risk of macrovascular disease as much as the duration of clinical diabetes itself.

Adult↗
PubMed1990

Type II diabetes and its complications in Mexican Americans.

The prevalence and incidence of type II diabetes are substantially higher in Mexican Americans than in non-Hispanic whites. This, combined with its earlier age of onset and the younger age structure of the Mexican American population, makes diabetes a major public health problem in this ethnic group and one which to a greater extent than in non-Hispanics strikes people in the prime of life. Both genetic and environmental factors undoubtedly contribute to this epidemic. The environmental factors would appear to be those commonly associated with the phenomenon of "modernization" or "westernization", namely, dietary change and adoption of sedentary lifestyles. As such, they are potentially modifiable and amenable to clinical and public health action. There is as yet no proof from clinical trials that modification of any or all of these environmental factors will in fact prevent diabetes. When clinical trials are performed, high-risk populations such as Mexican Americans should be considered as potential target populations, because of both the public health relevance and the lower sample size requirements in such populations. Further advances in identifying genetic susceptibles would also facilitate the design and execution of such trials. The increased risk of microvascular complications in Mexican American diabetics puts this population in "double jeopardy", i.e., they have a greater risk of acquiring diabetes in the first instance, and, having acquired it, they have a greater risk of suffering from its complications. It is still not clear whether the increased risk of complications in this ethnic group stems from an intrinsically more severe biological process or barriers to adequate medical care and/or poor compliance. Prospective data currently being gathered should help to resolve this issue. Assuming that medical care plays a role, a major opportunity--and challenge--exists to reduce substantially the morbidity, mortality, and economic burden associated with type II diabetes and its complications in the Mexican American population.

Diabetes Mellitus, Type 2↗
PubMed1990

Diminished insulin sensitivity and increased insulin response in nonobese, nondiabetic Mexican Americans.

The contributions of diminished insulin sensitivity and decreased insulin response to the development of non-insulin-dependent diabetes mellitus (NIDDM) remain controversial. Nondiabetics in high-risk populations for NIDDM, including Pima Indians and Mexican Americans, are characterized by obesity and hyperinsulinemia relative to nondiabetics in the lower-risk white population. However, it is not clear to what extent diminished insulin sensitivity in the high-risk groups reflects obesity per se or is an inherent characteristic of these groups. Insulin sensitivity and secretion were determined in 10 nonobese, normoglycemic Mexican Americans (mean body mass index [BMI], 23.8 kg/m2) and 11 normoglycemic non-Hispanic whites (mean BMI, 22.5 kg/m2) using the intravenous glucose tolerance test (IVGTT) and the minimal model approach of Bergman et al. Age, BMI, sum of skinfolds, and the ratio of waist-to-hip circumference (WHR) were similar in both ethnic groups. Mexican Americans had decreased insulin sensitivity compared with non-Hispanic whites (4.06 +/- 0.72 in Mexican Americans v 7.56 +/- 1.13 in non-Hispanic whites, P = .017). The areas under the C-peptide and insulin curves were significantly greater in Mexican Americans than in non-Hispanic whites (P less than .01), suggesting greater insulin secretion in the former. This study provides evidence for diminished insulin sensitivity and increased insulin response in young, nonobese, normoglycemic Mexican Americans.

Analysis of Variance↗