Josefina Medina-Lezama

Ethnic Differences in Arterial Wave Reflections and Normative Equations for Augmentation Index

Data regarding ethnic differences in wave reflections, which markedly affect the central pressure profile, are very limited. Furthermore, because age, heart rate, and body height are strong determinants of augmentation index, relating single measurements to normative data (in which augmentation index values correspond with average population values of its determinants) is challenging. We studied subject-level data from 10 550 adults enrolled in large population-based studies. In a healthy reference sample (n=3497), we assessed ethnic differences in augmentation index (ratio of second/first systolic peaks) and generated equations for adjusted z scores, allowing for a standardized comparison between individual augmentation index measurements and the normative population mean from subjects of the same age, sex, ethnic population, body height, and heart rate. After adjustment for age, body height, heart rate, and mean arterial pressure, African blacks (women: 154%; men: 138%) and Andean Hispanics (women: 152%; men: 133%) demonstrated higher central (aortic) augmentation index values than British whites (women: 140%; men: 128%), whereas American Indians (women: 133%; men: 122%) demonstrated lower augmentation index (all P<0.0001), without significant differences between Chinese and British whites. Similar results were found for radial augmentation index. Nonlinear ethnic/sex-specific equations for z scores were successfully generated to adjust individual augmentation index values for age, body height, and heart rate. Marked ethnic differences in augmentation index exist, which may contribute to ethnic differences in hypertensive organ damage. Our study provides normative data that can be used to complement the interpretation of individual hemodynamic assessments among men and women of various ethnic populations, after removing the effect of various physiological determinants.

Major Cardiovascular Risk Factors in Latin America: A Comparison with the United States. The Latin American Consortium of Studies in Obesity (LASO)

Background Limited knowledge on the prevalence and distribution of risk factors impairs the planning and implementation of cardiovascular prevention programs in the Latin American and Caribbean (LAC) region. Methods and Findings Prevalence of hypertension, diabetes mellitus, abnormal lipoprotein levels, obesity, and smoking were estimated from individual-level patient data pooled from population-based surveys (1998–2007, n = 31,009) from eight LAC countries and from a national survey of the United States (US) population (1999–2004) Age and gender specific prevalence were estimated and age-gender adjusted comparisons between both populations were conducted. Prevalence of diabetes mellitus, hypertension, and low high-density lipoprotein (HDL)-cholesterol in LAC were 5% (95% confidence interval [95% CI]: 3.4, 7.9), 20.2% (95% CI: 12.5, 31), and 53.3% (95% CI: 47, 63.4), respectively. Compared to LAC region’s average, the prevalence of each risk factor tended to be lower in Peru and higher in Chile. LAC women had higher prevalence of obesity and low HDL-cholesterol than men. Obesity, hypercholesterolemia, and hypertriglyceridemia were more prevalent in the US population than in LAC population (31 vs. 16.1%, 16.8 vs. 8.9%, and 36.2 vs. 26.5%, respectively). However, the prevalence of low HDL-cholesterol was higher in LAC than in the US (53.3 vs. 33.7%). Conclusions Major cardiovascular risk factors are highly prevalent in LAC region, in particular low HDL-cholesterol. In addition, marked differences do exist in this prevalence profile between LAC and the US. The observed patterns of obesity-related risk factors and their current and future impact on the burden of cardiovascular diseases remain to be explained.

Interethnic differences in the accuracy of anthropometric indicators of obesity in screening for high risk of coronary heart disease

Background:Cut points for defining obesity have been derived from mortality data among Whites from Europe and the United States and their accuracy to screen for high risk of coronary heart disease (CHD) in other ethnic groups has been questioned.Objective:To compare the accuracy and to define ethnic and gender-specific optimal cut points for body mass index (BMI), waist circumference (WC) and waist-to-hip ratio (WHR) when they are used in screening for high risk of CHD in the Latin-American and the US populations.Methods:We estimated the accuracy and optimal cut points for BMI, WC and WHR to screen for CHD risk in Latin Americans (n=18 976), non-Hispanic Whites (Whites; n=8956), non-Hispanic Blacks (Blacks; n=5205) and Hispanics (n=5803). High risk of CHD was defined as a 10-year risk ⩾20% (Framingham equation). The area under the receiver operator characteristic curve (AUC) and the misclassification-cost term were used to assess accuracy and to identify optimal cut points.Results:WHR had the highest AUC in all ethnic groups (from 0.75 to 0.82) and BMI had the lowest (from 0.50 to 0.59). Optimal cut point for BMI was similar across ethnic/gender groups (27 kg/m2). In women, cut points for WC (94 cm) and WHR (0.91) were consistent by ethnicity. In men, cut points for WC and WHR varied significantly with ethnicity: from 91 cm in Latin Americans to 102 cm in Whites, and from 0.94 in Latin Americans to 0.99 in Hispanics, respectively.Conclusion:WHR is the most accurate anthropometric indicator to screen for high risk of CHD, whereas BMI is almost uninformative. The same BMI cut point should be used in all men and women. Unique cut points for WC and WHR should be used in all women, but ethnic-specific cut points seem warranted among men.

Endogenous Nitric Oxide Synthase Inhibitors, Arterial Hemodynamics, and Subclinical Vascular Disease: The PREVENCION Study

Endogenous NO synthase inhibitors (end-NOSIs) have been associated with cardiovascular risk factors and atherosclerosis. In addition, end-NOSIs may directly cause hypertension through hemodynamic effects. We aimed to examine the association between end-NOSI asymmetrical dimethylarginine (ADMA) and N-guanidino-monomethyl-arginine (NMMA), subclinical atherosclerosis, and arterial hemodynamics. We studied 922 adults participating in a population-based study (PREVENCION Study) and examined the correlation between end-NOSI/l-arginine and arterial hemodynamics, carotid-femoral pulse wave velocity, and carotid intima-media thickness using linear regression. ADMA, NMMA, and l-arginine were found to be differentially associated with various classic cardiovascular risk factors. ADMA and NMMA (but not l-arginine) were significant predictors of carotid intima-media thickness, even after adjustment for cardiovascular risk factors, C-reactive protein, and renal function. In contrast, ADMA and NMMA did not predict carotid-femoral pulse wave velocity, blood pressure, or hemodynamic abnormalities. Higher l-arginine independently predicted systolic hypertension, higher central pulse pressure, incident wave amplitude, central augmented pressure, and lower total arterial compliance but not systemic vascular resistance or cardiac output. We conclude that ADMA and NMMA are differentially associated with cardiovascular risk factors, but both end-NOSIs are independent predictors of carotid atherosclerosis. In contrast, they are not associated with large artery stiffness, hypertension, or hemodynamic abnormalities. Our findings are consistent with a role for asymmetrical arginine methylation in atherosclerosis but not in large artery stiffening, hypertension, or long-term hemodynamic regulation. l-Arginine is independently associated with abnormal pulsatile (but not resistive) arterial hemodynamic indices, which may reflect abnormal l-arginine transport, leading to decreased intracellular bioavailability for NO synthesis.

The Latin American Consortium of Studies in Obesity (LASO).

Current, high‐quality data are needed to evaluate the health impact of the epidemic of obesity in Latin America. The Latin American Consortium of Studies of Obesity (LASO) has been established, with the objectives of (i) Accurately estimating the prevalence of obesity and its distribution by sociodemographic characteristics; (ii) Identifying ethnic, socioeconomic and behavioural determinants of obesity; (iii) Estimating the association between various anthropometric indicators or obesity and major cardiovascular risk factors and (iv) Quantifying the validity of standard definitions of the various indexes of obesity in Latin American population. To achieve these objectives, LASO makes use of individual data from existing studies. To date, the LASO consortium includes data from 11 studies from eight countries (Argentina, Chile, Colombia, Costa Rica, Dominican Republic, Peru, Puerto Rico and Venezuela), including a total of 32 462 subjects. This article describes the overall organization of LASO, the individual studies involved and the overall strategy for data analysis. LASO will foster the development of collaborative obesity research among Latin American investigators. More important, results from LASO will be instrumental to inform health policies aiming to curtail the epidemic of obesity in the region.

Prevalence of lifestyle-related cardiovascular risk factors in Peru: the PREVENCION study

OBJECTIVES To estimate the prevalence of lifestyle-related cardiovascular risk factors in the adult population of Arequipa, the second largest city in Peru. METHODS The prevalence and patterns of smoking, alcohol drinking, lack of physical activity, high-fat diet, and low fruit and vegetable intake were evaluated among 1 878 subjects (867 men and 1 011 women) in a population-based study. RESULTS The age-standardized prevalence of current smoking, former smoking, and never smoking were 21.6%, 14.3%, and 64.1%, respectively. The prevalence of current smoking was significantly higher in men than women (31.1% vs. 12.1%; P < 0.01). The prevalence of current alcohol use was 37.7% and significantly higher in men than women (55.5% vs. 19.7%; P < 0.01). Similarly, the prevalence of binge drinking was 21.2%, and the percentage of men who binge drink (36.1%) was significantly higher than for women (6.4%; P < 0.01). The vast majority of alcohol drinkers reported a pattern of alcohol consumption mainly on weekends and holidays rather than regular drinking with meals during the week. The proportion of insufficiently active people was 57.6% and was significantly higher in women than men (63.3% vs. 51.9%; P < 0.01). Overall, 42.0% of adults reported consuming high-fat diets, 34.5% reported low fruit intake, and 33.3% reported low vegetable intake. CONCLUSIONS The high prevalence of lifestyle-related cardiovascular risk factors found in this Andean population is of concern. Preventive programs are urgently needed to deal with this growing problem.

Optimal Definitions for Abdominal Obesity and the Metabolic Syndrome in Andean Hispanics: The PREVENCION Study

OBJECTIVE We aimed to establish optimal definitions for abdominal obesity and metabolic syndrome (MetS) among Andean adults. RESEARCH DESIGN AND METHODS Among 1,448 Andean adults, we assessed the relationship between waist circumference and subclinical vascular disease assessed by carotid intima-media thickness (cIMT) and manifest cardiovascular disease (M-CVD). RESULTS Optimal waist circumference cutoffs to classify individuals with abnormal cIMT or M-CVD were >97 and >87 cm in men and women, respectively. With these cutoffs, there was substantial disagreement between the original American Heart Association/National Heart, Lung and Blood Institute (AHA/NHLBI) and the recently updated MetS definition, particularly among men (κ = 0.85). Subjects with MetS identified by the updated definition but not meeting the original AHA/NHLBI MetS criteria demonstrated significantly increased cIMT (P < 0.001) compared with subjects who did not meet the MetS criteria by either definition. CONCLUSIONS Our findings support the use of ethnic-specific waist circumference cutoffs and the updated MetS definition in Andean adults.

Normative values and correlates of carotid artery intima-media thickness and carotid atherosclerosis in Andean-Hispanics: The Prevencion Study

OBJECTIVES Carotid intima-media thickness (cIMT) is an independent predictor of cardiovascular risk. Furthermore, ethnicity and gender-specific normative data are required to assess cIMT, which are not available for Andean-Hispanics. In addition, data regarding correlates of subclinical atherosclerosis in ethnic population are needed. METHODS We studied 1448 adults enrolled in a population-based study in Peru. cIMT and carotid plaque were measured with high-resolution ultrasonography. A healthy reference sample (n=472) with no cardiovascular disease, normal weight and normal metabolic parameters was selected to establish normative cIMT values. Correlates of abnormal cIMT and carotid plaque were assessed in the entire population. RESULTS In the reference sample, 95th-percentile cIMT values were both age and gender-dependent. In stepwise regression, selected predictors of increasing cIMT were: older age, impaired fasting glucose, diabetes mellitus, higher systolic blood pressure, higher LDL-cholesterol, smoking and male gender. Predictors of carotid plaque included older age, male gender, higher systolic blood pressure, lower diastolic blood pressure and higher LDL-cholesterol. HDL-cholesterol and C-reactive protein were not associated with cIMT or carotid plaque. The lack of association with HDL-cholesterol was confirmed using high performance liquid chromatography. CONCLUSIONS We present ethnic-specific cut-offs for abnormal cIMT applicable to Andean-Hispanics and correlates of subclinical atherosclerosis in this population. Pending longitudinal studies, our data supports several risk associations seen in other populations and can be used to identify Andean-Hispanics at increased risk for atherosclerotic cardiovascular disease. The lack of association between HDL-C and cIMT or carotid plaque in this population requires further investigation.

Prevalence and patterns of hypertension in Peruvian Andean Hispanics: the PREVENCION study

Cardiovascular disease is emerging as a leading cause of morbidity and mortality in Latin America. Population-based data regarding the prevalence of hypertension and hypertension subtypes in Andean Hispanic populations are scarce. The authors performed a population-based study that included 1878 Peruvian Andean adults to determine: (1) the prevalence, awareness, and control of hypertension and (2) the relative frequency of hypertension subtypes (systolic vs. diastolic). The prevalence of hypertension was 15.7% (95% confidence interval [CI], 14.0%-17.4%), did not differ by gender, and increased steeply with age, particularly in women. Awareness, treatment, and control rates were 47.9%, 39.5%, and 14%, respectively. Diastolic blood pressure increased until age 50 years and reached a plateau thereafter, whereas mean arterial pressure continued to increase with age even after age 50 years. Furthermore, in sharp contrast with the United States population, the predominant type of hypertension was systodiastolic (41.7%; 95% CI, 35.1%-48.5%). Isolated systolic hypertension accounted for only 29.3% of cases (95% CI, 23.9%-35.4%) and was responsible for a minority of cases in all age groups before age 70 years. Hypertension subtypes in this Andean population seem to differ significantly from those present in the United States population, with a much larger proportion of systodiastolic and diastolic hypertension even with advanced age. These differences result from interactions between hemodynamic and structural factors, and further studies aimed at characterizing their genetic and environmental determinants and implications in end-organ damage and prognosis in this population may contribute to understanding the pathophysiology of hypertension.

Metabolic syndrome as an underlying disease entity and its relationship to subclinical atherosclerosis in Andean hispanics

BACKGROUND The question of whether the metabolic syndrome truly reflects a single disease entity with a common underlying pathology remains unclear. In this study, we assess whether metabolic syndrome represents an underlying disease construct in a large population-based sample of Andean Hispanic adults and examine its relationship to subclinical atherosclerosis. METHODS The study sample was comprised of 2513 participants. Confirmatory factor analysis (CFA) was used to identify a metabolic syndrome latent factor using waist circumference, systolic and diastolic blood pressure, high-density lipoprotein cholesterol (HDL-C), triglycerides (TGs), and glucose levels as indicators. The relationship with subclinical atherosclerosis, measured by carotid intima media thickness (cIMT), was assessed using structural equation modeling. RESULTS Results supported the proposed structure of the metabolic syndrome latent factor evidenced by adequate fit indexes. HDL-C did not significantly load on the metabolic syndrome latent factor (standardized factor loading=0.01, P=0.88). The metabolic syndrome latent factor was significantly associated with cIMT in women (B=0.007, P<0.001) and men (B=0.008, P<0.001) after controlling for age, low-density lipoprotein cholesterol and smoking. CONCLUSIONS Our findings suggest that metabolic syndrome components, such as waist circumference, blood pressure, TGs, and glucose levels, but not HDL-C, share a common underlying pathophysiology that may contribute to the progression of atherosclerosis in Andean Hispanics. Its longitudinal association with cardiovascular disease should be the focus of future research.