Factor Analysis of Clustered Cardiovascular Risks in Adolescence

The influence of adolescent body mass index, physical activity, and tobacco use on blood pressure and cholesterol in young adulthood

PURPOSE

To test the independent influences of adolescent tobacco use, physical activity/inactivity, and body mass index (BMI) on young adult cardiovascular risk factors.

METHODS

This is a prospective cohort study using data from Waves I and III of the National Longitudinal Study of Adolescent Health (Add Health) (N = 14,322). We tested whether Wave I tobacco use, physical activity/inactivity, and BMI predicted self-report of being diagnosed with high blood pressure (BP) or high cholesterol by Wave III, while controlling for gender, age, race/ethnicity, use of healthcare, and Wave III tobacco use, physical activity/inactivity, BMI.

RESULTS

Among young adults aged 18-26, 5.37% report high BP and 4.28% high cholesterol. Obese adolescents are more likely to report high BP by young adulthood than normal-weight adolescents, independent of all control variables including BMI in young adulthood (adjusted odds ratio [aOR] = 1.96; 95% confidence interval = [1.50-2.57]). Overweight and obese adolescents are more likely to report high cholesterol by young adulthood than normal-weight adolescents, independent of all control variables including BMI in young adulthood (aOR = 1.47 [1.14-1.90] and 2.05 [1.44-2.91], respectively). Adolescent tobacco use and physical activity/inactivity do not independently predict reported high BP or cholesterol.

CONCLUSIONS

The odds of overweight and obese adolescents reporting a diagnosis for two cardiovascular risk factors by young adulthood are 1.5 to two times higher than normal-weight adolescents, regardless of BMI in young adulthood. The impact of transient and sustained increases in adolescent BMI on the evolution of cardiovascular risk warrants further investigation.

Latent common genetic components of obesity traits

Background

Obesity is rapidly becoming a global epidemic. Unlike many complex human diseases, obesity is defined not just by a single trait or phenotype, but jointly by measures of anthropometry and metabolic status.

Methods

We applied maximum likelihood factor analysis to identify common latent factors underlying observed covariance in multiple obesity-related measures. Both the genetic components and the mode of inheritance of the common factors were evaluated. A total of 1775 participants from 590 families for whom measures on obesity-related traits were available were included in this study.

Results

The average age of participants was 37 years, 39% of the participants were obese (body mass index ≥ 30.0 kg/m²) and 26% were overweight (body mass index 25.0 - 29.9 kg/m²). Two latent common factors jointly accounting for over 99% of the correlations among obesity-related traits were identified. Complex segregation analysis of the age and sex-adjusted latent factors provide evidence for a Mendelian mode of inheritance of major genetic effect with heritability estimates of 40.4% and 47.5% for the first and second factors, respectively.

Conclusions

These findings provide a support for multivariate-based approach for investigating pleiotropic effects on obesity-related traits which can be applied in both genetic linkage and association mapping.

Training health care professionals to manage overweight adolescents: experience in rural Georgia communities

CONTEXT

The obesity epidemic threatens the present and future health of adolescents in the United States. Yet, health care providers lack specific training for pediatric obesity assessment and management.

PURPOSE

This study examined the adherence of rural Georgia primary care practitioners to an overweight adolescent management protocol. The study also documented the prevalence of obesity-associated physiological and behavioral risk factors among overweight adolescent patients.

METHODS

Ten rural clinics (58 providers) were recruited and received a 90-minute adolescent overweight assessment and management training session. Select biochemical, dietary, physical activity, and physical inactivity behaviors were assessed in overweight adolescent patients. Medical charts were abstracted to assess practitioner compliance with an overweight assessment protocol and patient adherence to a 16-week follow-up visit.

FINDINGS

Providers were receptive to training and complied with the recommended protocol. Eighty-five overweight adolescents were assessed, but only 49 (57%) completed the scheduled 16-week follow-up visit. Physical, biochemical, and behavioral assessments revealed that 13%-27% of the participants had abnormal levels of lipids, fasting glucose, and glucose/insulin ratio, and 80.5% had waist circumferences above the 90th percentile.

CONCLUSIONS

Practitioners complied with the assessment and follow-up protocol, leading to the discovery of previously unrecognized risk factors in many overweight adolescent patients. Lack of patient adherence to follow-up was the greatest limiting factor for obesity management. Further efforts are needed to implement and evaluate training to improve the management of adolescent overweight, especially in rural communities.

A cumulative risk model predicting caregiver quality of life in pediatric asthma

OBJECTIVE

To examine the relationship between a cumulative risk model and caregiver quality of life (QOL) in pediatric asthma and determine whether caregiver QOL is predicted by a linear or quadratic model of cumulative risk.

METHODS

One hundred and ninety-three families of children between the ages of 5 and 12 years with mild to severe asthma completed a background questionnaire and measures of QOL, asthma severity, family burden, and family stress. A cumulative risk model based on risk factors from these measures was calculated for each caregiver.

RESULTS

The cumulative risk model significantly predicted caregiver QOL as a quadratic function. Caregivers with numerous risk factors experienced a dramatic worsening of QOL.

CONCLUSIONS

Findings suggest that caregiver QOL is best predicted by the interaction and not the summation of these factors. Interventions focused on one area of family risk may be effective in reducing poor QOL in caregivers of children with asthma.

Defining the metabolic syndrome in children and adolescents: will the real definition please stand up?

OBJECTIVES

To review the use of definitions of the metabolic syndrome in studies of children and adolescents and to review results from studies that used factor analysis to examine structure among cardiometabolic variables.

STUDY DESIGN

Literature review.

RESULTS

In 27 publications, authors used 40 unique definitions of the metabolic syndrome. Most of these definitions were adaptations of the adult definition developed by the National Cholesterol Education Program. In 11 studies that used exploratory factor analysis, the number of components ranged from 5 to 19, and the number of factors identified ranged from 1 to 5.

CONCLUSIONS

The use of multiple definitions of the metabolic syndrome argues strongly for the development of a standard pediatric definition.

Assessment of minerals in obesity-related diseases in the Chandigarh (India) population

Excessive Zn but normal Cu and Mg in the staple food consumed by the people of Chandigarh (Union territory and capital of Punjab and Haryana States of India) has been considered to be the major risk factor for the prevalence of obesity (33.15%) and obesity-related diseases in this region. Therefore, in the present investigations, in obesity-related diseases, the status of these minerals was estimated in their tissues, including hair, nails, and blood serum and urine, and compared with those of normal subjects. They were grouped as: normal subjects in control Group A, middle-aged diabetics in Group D(M), older diabetics in Group D(O), and diabetics with osteoarthritis in Group D+ OA, osteoarthritis in Group OA and rheumatoid arthritis in Group RA, respectively. The results evaluated in the order as: hair Zn, group D+OA>D(M)>OA>A (control)>RA>D(O) (p < 0.001); hair Cu, group A (control)>D(M)>OA>D+OA>D(O)>RA (p < 0.001); hair Mg, group A (control)>D(M)>OA>D+OA>RA>D(O) (p < 0.001, 0.01); hair Mn, group A (control)>RA>OA>D-OA>D(M)>D(O) (p < 0.001); nail Zn, group D(M)>D+OA>OA>A (control)>RA>D(O) (p < 0.001, 0.05); nail Cu, group A (control)>OA>D(M)>D+OA>RA>D(O) (p < 0.001); nail Mg, group A (control)>OA>D(M)>D(O)>D+OA >RA (p < 0.001); nail Mn, group A (control) >RA>OA>D+OA>D(M)>D(O) (p < 0.01); urine Zn, group D(O)>D(M)>D+OA>A (control)>RA>OA (p < 0.01); urine Cu, group RA>D+OA>D(O)>OA> D(M)>A (control) (p<0.001); urine Mg, group RA>OA>D+OA>D(O)>D(M)>A (control; p < 0.001); urine Mn, group D(O)>D(M)>OA>D+OA>RA>A (control; p < 0.001), respectively. The analysis of the mineral status in serum of diabetics further showed their highly significant rise from lower mean age subgroup to higher mean age subgroup than their control counter parts (p < 0.001, 0.01, and 0.05) with coincident deficiencies of Cu, Mg, and Mn in their tissues. This study would be helpful considering the status of minerals in these obesity-related diseases depending on the choice of the food consumed to improve the quality of life and prognosis for the diseases.

Metabolic syndrome rates in United States adolescents, from the National Health and Nutrition Examination Survey, 1999-2002

OBJECTIVE

To report the prevalence rates of the metabolic syndrome in a nationally representative sample of adolescents in the United States using 4 previously reported definitions of the syndrome.

STUDY DESIGN

Data from 12- to 19-year-old adolescents included in the National Health and Nutrition Examination Survey from 1999 to 2002 (NHANES 99-02) were analyzed by cross-sectional methods, by using 4 definitions of the metabolic syndrome previously applied to adolescents.

RESULTS

In NHANES 99-02, the prevalence of the metabolic syndrome in all teens varied from 2.0% to 9.4% of teens in the United States, depending on the definition used. In obese teens, these prevalence rates varied from 12.4% to 44.2%. In the group of obese teens, application of the definition by Cruz produced a metabolic syndrome prevalence rate of 12.4%; that of Caprio produced a rate of 14.1%. However, none of the normal weight or overweight teens met either definition. Application of the definition by Cook produced a prevalence rate of 7.8% in overweight teens and 44% in obese teens. The adult definition of metabolic syndrome produced a prevalence rate of 16% in overweight teens and 26% in obese teens.

CONCLUSIONS

In the period between 1999 and 2002, the prevalence rate of metabolic syndrome varied from just >9% to as low as 2% of adolescents overall. Different definitions of metabolic syndrome generated prevalence rates in obese adolescents that varied widely from 12% to 44%. For this syndrome to be a useful construct, a more standardized set of criteria may be needed.

Physical Activity: The Epidemic of Obesity and Overweight Among Youth: Trends, Consequences, and Interventions

Childhood and adolescent overweight and obesity are an epidemic problem in the United States. Studies show that approximately one third of youth are overweight or obese, representing a tripling since the 1960s and 1970s. The average male and female adult in the United States has gained 25 lbs and 24 lbs, respectively, since 1962. The body mass index of the average adult has increased from 25 to 28. Among youth, the average body mass index has increased from 21.3 to 24.1 since 1963. This increase in bodyweight among adults and youth is partially due to the decreased levels of physical activity. The economic and health consequences of this epidemic are enormous. Type 2 diabetes mellitus, a disease that was rare among youth 20 to 30 years ago, now represents as many as 45% of all cases of diabetes among youth. Cardiovascular risk factors are worsened in overweight and obese youth, and early evidence of atherosclerosis manifested by endothelial dysfunction and increased coronary artery calcium is present in a high percentage of overweight youth. Numerous psychosocial problems also are increased among overweight and obese youth. However, there are numerous examples in the scientific literature of successful approaches to the prevention and management of overweight and obesity in youth. This article summarizes statistics concerning the prevalence of overweight, obesity, and physical inactivity among youth; discusses the numerous physical and psychosocial consequences of overweight and obesity among youth; and presents information regarding interventions that have been demonstrated to be effective in preventing childhood and adolescent overweight and obesity.

Metabolic syndrome pandemic

The metabolic syndrome is a multiplex risk factor that consists of several risk correlates of metabolic origin. In addition, to dyslipidemia, hypertension, and hyperglycermia, the syndrome carries a prothrombotic state and a proinflammatory state. Persons with the metabolic syndrome are at essentially twice the risk for cardiovascular disease compared with those without the syndrome. It further raises the risk for type 2 diabetes by about 5-fold. Although some investigators favor keeping risk factors separate for purposes of clinical management, others believe that identifying individuals with an aggregation of risk factors provides additional useful information to guide clinical management. In particular it focuses attention on obesity and sedentary life habits that are the root of the syndrome. This review addresses the prevalence of this clustering phenomenon throughout the world. Such seems appropriate because of the increasing prevalence of obesity in almost all countries. The available evidence indicates that in most countries between 20% and 30% of the adult population can be characterized as having the metabolic syndrome. In some populations or segments of the population, the prevalence is even higher. On the other hand, in parts of developing world in which young adults predominate, the prevalence is lower; but with increasing affluence and aging of the population, the prevalence undoubtedly with rise.

Thinness, overweight and obesity in a national sample of Iranian children and adolescents: CASPIAN Study

BACKGROUND

This study was conducted to assess the national prevalence of different grades of nutritional status (underweight, normal weight, overweight and obesity) among Iranian school-students and to compare the prevalence of overweight and obesity using three different sets of criteria.

METHODS

This cross-sectional national survey was conducted on a representative sample of 21 111 school students including 10 253 boys (48.6%) and 10 858 girls (51.4%) aged 6-18 years, selected by multistage random cluster sampling from urban (84.6%) and rural (15.4%) areas of 23 provinces in Iran The percentage of subjects in the corresponding body mass index (BMI) categories of the Centers of Disease Control and Prevention (CDC), the International Obesity Task Force (IOTF) and the obtained national percentiles were assessed and compared.

RESULTS

There was no gender differences in BMI, but was higher in boys living in urban than in rural areas (18.4 +/- 3.88 vs. 17.86 +/- 3.66 kg/m(2) respectively, P < 0.05). The prevalence of underweight was 13.9% (8.1% of boys and 5.7% of girls) according to the CDC percentiles, and 5% (2.6% of boys and 2.4% of girls) according to the obtained percentiles. According to the CDC, IOTF and national cut-offs, the prevalence of overweight was 8.82%, 11.3% and 10.1% respectively; and the prevalence of obesity was 4.5%, 2.9% and 4.79% respectively. The prevalence of overweight was highest (10.98%) in the 12-year-old group and that of obesity (7.81%) in the 6-year-old group. The kappa correlation coefficient was 0.71 between the CDC and IOTF criteria, 0.64 between IOTF and national cut-offs, and 0.77 between CDC and national cut-offs.

CONCLUSIONS

The findings of this study warrant the necessity of paying special attention to monitoring of the time trends in child obesity based on uniform definitions, as well as to design programmes to prevent and control associated factors.

Microcirculation in obesity: an unexplored domain

Obesity is traditionally linked to diabetes and cardiovascular diseases. Very recent experimental, clinical and epidemiological, sometimes provocative, data challenge this automaticity by showing that not the amount but the distribution of fat is the important determinant. Moderate abdominal fat accumulation may thus be more harmful than even consequent overweight. In view of the worldwide burden of obesity, factors leading to it in children and young adults must urgently be identified. Since obesity is a very complex cardiometabolic situation, this will require to focus investigations on uncomplicated obese subjects and adequate animal models. The recent discovery of intergenerational transmissions of obesity risk factors and also the key role played by gestational and perinatal events (epigenetic factors) give rise to completely new concepts and research avenues. Considering the potential close relationship between microcirculation and tissue metabolism, demonstrations of structural and/or functional abnormalities in microvascular physiology very early in life of subjects at risk for obesity might provide a solid basis for further investigations of such links. Microcirculation(arterioles, capillaries and venules) is conceivably a key compartment determining over one or several decades the translation of genetic and epigenetic factors into fat accumulation. Available animal models should serve to answer this cardinal question.

Metabolic syndrome in youth: a cross-sectional school-based survey

AIM

To assess the prevalence of metabolic syndrome (MetS) among students attending vocational secondary school (VSE). VSE provides practice-oriented education in which young people learn a specific occupation. Previously we reported VSE to be the type of education with the highest prevalence of overweight and obesity.

METHODS

All data were collected in a cross-sectional school-based survey. Subjects were recruited from a community sample of 869 adolescents in 14 secondary schools. In this total sample all components of the metabolic syndrome were assessed in a subgroup of 506 students. MetS was defined analogous to National Cholesterol Education Program: Adult Treatment Panel III criteria, with modifications for students under 19 years of age.

RESULTS

In the subsample (n=506) 4.1% of the students had metabolic syndrome. There was a significant difference in the prevalence of metabolic syndrome among BMI categories (p<0.001). The prevalence of metabolic syndrome was higher in obese students (39.1%) than in overweight students (2.8%) and normal weight students (0.3%).

CONCLUSION

Being overweight or obese substantially increases the risk for metabolic syndrome, even in an adolescent school population.

General and visceral adiposity in black and white adolescents and their relation with reported physical activity and diet

BACKGROUND

Excess body fat accumulation may begin in youth and is linked with increased risk of cardiovascular disease. Examination of physical activity (PA) and diet behaviours predictive of adiposity may help target efforts to reduce chronic disease risk.

OBJECTIVE

We hypothesized that energy intake (EI) from fat, vigorous PA (VPA), and their interaction would predict body fat percentage (%BF) and visceral adipose tissue (VAT) in youth and that sedentary behaviours and intake of dairy, fruit, vegetable and whole grain foods would be related to adiposity.

DESIGN

A cross-sectional, observational study of reported PA and diet behaviours and objective adiposity measures.

SUBJECTS

Six-hundred sixty-one healthy black and white adolescents aged 14-18 years.

MEASUREMENTS

Diet by 24-h recalls using Nutrition Data Systems for Research (Minneapolis, MN, USA), VPA by previous day physical activity recalls (PAR), and %BF with dual-energy X-ray absorptiometry. VAT by magnetic resonance imaging for 434 subjects.

RESULTS

Reported EI and VPA were positively correlated with each other and were negative predictors of %BF. Time spent watching television or movies and %EI from protein were positive predictors of %BF. Adjusted for EI, none of the independent variables predictive of %BF retained their significance. %BF and VAT were highly correlated (r=0.73, P<0.0001). EI was the sole and negative predictor of VAT.

CONCLUSIONS

Higher energy 'throughput', not energy restriction, characterize leaner youths. Youths should be advised to engage in VPA so that they can eat sufficient calories to obtain the nutrients required for optimal health while remaining lean.

Metabolic risk-factor clustering estimation in children: to draw a line across pediatric metabolic syndrome

BACKGROUND

The diagnostic criteria of the metabolic syndrome (MS) have been applied in studies of obese adults to estimate the metabolic risk-associated with obesity, even though no general consensus exists concerning its definition and clinical value. We reviewed the current literature on the MS, focusing on those studies that used the MS diagnostic criteria to analyze children, and we observed extreme heterogeneity for the sets of variables and cutoff values chosen.

OBJECTIVES

To discuss concerns regarding the use of the existing definition of the MS (as defined in adults) in children and adolescents, analyzing the scientific evidence needed to detect a clustering of cardiovascular risk-factors. Finally, we propose a new methodological approach for estimating metabolic risk-factor clustering in children and adolescents.

RESULTS

Major concerns were the lack of information on the background derived from a child's family and personal history; the lack of consensus on insulin levels, lipid parameters, markers of inflammation or steato-hepatitis; the lack of an additive relevant effect of the MS definition to obesity per se. We propose the adoption of 10 evidence-based items from which to quantify metabolic risk-factor clustering, collected in a multilevel Metabolic Individual Risk-factor And CLustering Estimation (MIRACLE) approach, and thus avoiding the use of the current MS term in children.

CONCLUSION

Pediatricians should consider a novel and specific approach to assessing children/adolescents and should not simply derive or adapt definitions from adults. Evaluation of insulin and lipid levels should be included only when specific references for the relation of age, gender, pubertal status and ethnic origin to health risk become available. This new approach could be useful for improving the overall quality of patient evaluation and for optimizing the use of the limited resources available facing to the obesity epidemic.

An approach to the characterization of serum low-molecular weight proteins/peptides in liver injury using SELDI–TOF MS and factor analysis

OBJECTIVES

The objective of this work was to investigate if the application of factor analysis to the SELDI-TOF MS data could contribute to the characterization of the serum low-molecular weight proteins/peptides in liver injury.

DESIGN AND METHODS

Distinguished SELDI-TOF mass spectral peaks of the liver injury group were identified by comparing with those of the control group. Factor analysis was introduced to classify these peaks into different groups, assignable to the possible underlying factors. Based on original mass spectral plot, loading and current medical knowledge, the common characteristics of the peaks in same group were revealed and the underlying factors were tentatively defined.

RESULTS

The SELDI profiles of liver injury group exhibit 43 discriminating peaks from the control group. Factor analysis extracted 4 common factors, which were the cholestasis, coagulation, attenuation and 9292 factors. And a plausible interpretation for some undetermined peaks was proposed.

CONCLUSION

The application of factor analysis to SELDI-TOF MS data extracted valuable information out of complex and high-dimensional mass spectra data.

Television viewing and its association with overweight in Colombian children: results from the 2005 National Nutrition Survey: a cross sectional study

BACKGROUND

There has been an ongoing discussion about the relationship between time spent watching television and childhood obesity. This debate has special relevance in the Latin American region were the globalization process has increased the availability of screen-based entertainment at home. The aim of this study is to examine the association between television viewing and weight status in Colombian children.

METHODS

This cross sectional investigation included children aged 5 to12 yrs from the National Nutrition Survey in Colombia (ENSIN 2005). Weight and height were measured in 11,137 children in order to calculate body mass index. Overweight was defined by international standards. Time spent viewing television was determined for these children through parental reports. Multiple logistic regression analyses were conducted for different subgroups and adjusted for potential confounders in order to study the association between television viewing and weight status in this population.

RESULTS

Among the surveyed children, 41.5% viewed television less than two hours/day; 36.8% between two and 3.9 hours/day and 21.7% four or more hours/day. The prevalence of overweight (obesity inclusive) in this population was 11.1%. Children who were classified as excessive television viewers (between two and 3.9 hours/day or 4 or more hours/day) were more likely to be overweight (OR: 1.44 95% CI: 1.41-1.47 and OR: 1.32 95% CI: 1.30-1.34, respectively) than children who reported to watch television less than 2 hours/day. Stratified analyses by age, gender and urbanization levels showed similar results.

CONCLUSION

Television viewing was positively associated with the presence of overweight in Colombian children. A positive association between urbanization level and television viewing was detected. Considering that the majority of Colombian children lives in densely populated cities and appear to engage in excessive television viewing these findings are of public health relevance for the prevention of childhood obesity.

Low cardiorespiratory fitness is a strong predictor for clustering of cardiovascular disease risk factors in children independent of country, age and sex

BACKGROUND AND DESIGN

Few studies have investigated the association between maximal cardiorespiratory capacity (fitness) and the clustered cardiovascular disease (CVD) risk in children and youth from culturally diverse countries. This cross-sectional study examined the association between fitness and clustered CVD risk in children and adolescents from three European countries.

METHODS

Participants were 2845 randomly selected school children aged 9 or 15 years from Portugal (n=944), Denmark (n=849) and Estonia (n=1052). Cardiorespiratory fitness was determined during a maximal test on a cycle ergometer. CVD risk factors selected to assess the degree of clustering were the total cholesterol/high-density lipoprotein cholesterol ratio, plasma triglycerides, insulin resistance (homeostasis model assessment), sum of four skinfolds, and systolic blood pressure.

RESULTS

There was a strong association between cardiorespiratory fitness and the clustering of CVD risk factors. The odds ratios for clustering in each quartile of fitness, using the quartile with the highest fitness as reference, were 13.0 [95% confidence interval (CI) 8.8-19.1]; 4.8 (95% CI 3.2-7.1) and 2.5 (95% CI 1.6-3.8), respectively, after adjusting for country, age, sex, socio-economic status, pubertal stage, family history of CVD and diabetes. In stratified analyses by age group, sex and country, similar strong patterns were observed.

CONCLUSION

Low cardiorespiratory fitness is strongly associated with the clustering of CVD risk factors in children independent of country, age and sex.

Insulin resistance and clustering of cardiometabolic risk factors in urban teenagers in southern India

OBJECTIVE

We sought to study the occurrence of cardiometabolic risk variables, their clustering, and their association with insulin resistance among healthy adolescents in urban south India.

RESEARCH DESIGN AND METHODS

School children aged 12-19 years (n = 2,640; 1,323 boys and 1,317 girls) from diverse socioeconomic backgrounds were studied. Demographic, social, and medical details were obtained; anthropometry and blood pressure were measured. Fasting plasma glucose, insulin, and lipid profiles were measured. Clusters of risk variables were identified by factor analysis. Association of insulin resistance (homeostasis model assessment) with individual risk variables and their clusters were assessed.

RESULTS

One or more cardiometabolic abnormalities (i.e., low HDL cholesterol, elevated triglycerides, fasting plasma glucose, or blood pressure) was present in 67.7% of children (in 64.8% of normal weight and 85% of overweight children). Insulin resistance was associated with the above abnormalities except HDL cholesterol. It also showed significant positive association with BMI, waist circumference, body fat percentage, and total cholesterol (P < 0.0001). Factor analysis identified three distinct clusters, with minor differences in the sexes: 1) waist circumference and blood pressure; 2) dyslipidemia, waist circumference, and insulin; and 3) waist circumference, glucose, and plasma insulin, with minor differences in the sexes. Insulin was a component of the lipid and glucometabolic cluster. In girls, it was a component of all three clusters.

CONCLUSIONS

Cardiometabolic abnormalities are present in nearly 68% of young, healthy, Asian-Indian adolescents and even among those with normal weight. Insulin resistance is associated with individual cardiometabolic factors, and plasma insulin showed association with clustering of some variables.

Is there a single underlying factor for the metabolic syndrome in adolescents? A confirmatory factor analysis

OBJECTIVE

The lack of a universally applicable model for the metabolic syndrome in the pediatric population makes it difficult to define this syndrome and compare its prevalence across studies and diverse populations. We sought to assess whether a single underlying factor could represent the metabolic syndrome in adolescents.

RESEARCH DESIGN AND METHODS

Using data from the National Health and Nutrition Examination Survey (1999-2002), we conducted a confirmatory factor analysis to assess the validity of waist circumference, triglycerides, fasting insulin, and systolic blood pressure (SBP) as potential phenotypic traits for the metabolic syndrome in adolescents aged 12-17 years (n = 1,262). A multiple-group approach was used to test the invariance in factor loadings across sex and race/ethnicity.

RESULTS

The estimates of factor loadings for the total sample were 0.76, 0.46, 0.81, and 0.42 for waist circumference, triglycerides, fasting insulin, and SBP, respectively. The goodness-of-fit indexes were adequate for the total sample (comparative fit index, 0.99; standardized root mean square residual, 0.02), Caucasian boys (1.0; 0.01), African-American boys (0.99; 0.03), Mexican-American boys (1.0; 0.01), Mexican-American girls (1.0; 0.01), and Caucasian girls (0.95; 0.04) and acceptable for African-American girls (0.94; 0.05). There were no significant differences in factor loadings of the four measured variables between boys and girls and among the three racial or ethnic subgroups.

CONCLUSIONS

The metabolic syndrome as a single underlying factor for the four simple phenotypic traits may be plausible in adolescents. The proposed model appears to be generalizable across sex and race/ethnicity.

Platelet and White Blood Cell Counts Are Elevated in Patients With the Metabolic Syndrome

Platelet and white blood cell counts are higher among some insulin-resistant patients and may contribute to atherothromboembolic complications. Metabolic syndrome patients are insulin resistant, often hypertensive, and at high cardiovascular disease risk, yet the relationship of platelets to the metabolic syndrome is unknown. Platelet and white blood cell counts were obtained from 135 volunteers who had measurements of blood pressure, fasting triglycerides, high-density lipoprotein cholesterol, and glucose. A body mass index >30 kg/m2 served as a surrogate for increased waist circumference. Subjects were subdivided into three groups by the number of metabolic syndrome criteria, i.e., no metabolic syndrome risk factor (MS-0; n = 40), one or two metabolic syndrome risk factors (MS1-2; n = 61), and three to five metabolic syndrome risk factors (MS3-5; n = 34). Platelet counts were increased significantly from 226+/-8 to 257+/-8 and 276+/-10 (x10(3)/mm3) in the MS-0, MS1-2, and MS3-5 groups, respectively (p < 0.01), after adjustment for age, gender, ethnicity, total cholesterol, and low-density lipoprotein cholesterol. White blood cell counts were also increased across the three groups (5.4+/-0.2, 6.2+/-0.2, and 6.6+/-0.3 [x10(3)/mm3]; p < 0.01) after multivariate adjustment. Compared with patients with zero to two metabolic syndrome risk factors, metabolic syndrome patients have higher platelet and white blood counts, which may serve as markers of a prothrombotic and proinflammatory state and contributors to atherothromboembolic risk.

Biomarkers of obesity and subsequent cardiovascular events

Obesity is a major risk factor for cardiovascular diseases, but the mechanisms for increased cardiovascular risk in obesity are still unclear. Inflammation and increased oxidative stress are two potential mechanisms proposed to play a major role in the morbidity associated with obesity. Studies that investigate these mechanisms rely on biomarkers, but validated biomarkers for obesity-related cardiovascular outcomes are lacking. By finding optimal biomarkers, diagnostic criteria for cardiovascular diseases can be refined in the obese beyond "traditional" risk factors to identify early pathologic processes. The objective of this review is to identify potential early biomarkers resulting from obesity and associated with cardiovascular disease. Studies were initially identified through the search engine PubMed by using the keywords "obesity" and "biomarker." Subsequently, combinations of the keywords "obesity," "biomarker," "cardiovascular risk," "adipose tissue," "adipokine," "adipocytokine," and "oxidative stress" were used. The SOURCE database and Online Mendelian Inheritance in Man (OMIM) were used to obtain more information on the biomarkers. Results of the searches yielded a large number of potential biomarkers that occur in obesity and which either correlate with traditional cardiovascular risk factors or predict subsequent cardiovascular events. Several biomarkers are promising regarding their biologic properties, but they require further validation in humans.

Instability in the diagnosis of metabolic syndrome in adolescents

BACKGROUND

Factor analyses suggest that the structure underlying metabolic syndrome is similar in adolescents and adults. However, adolescence is a period of intense physiological change, and therefore stability of the underlying metabolic structure and clinical categorization based on metabolic risk is uncertain.

METHODS AND RESULTS

We analyzed data from 1098 participants in the Princeton School District Study, a school-based study begun in 2001-2002, who were followed up for 3 years. We performed factor analyses of 8 metabolic risks at baseline and follow-up to assess stability of factor patterns and clinical categorization of metabolic syndrome. Metabolic syndrome was defined using the current American Heart Association/National Heart, Lung, and Blood Institute definition for adults (AHA), a modified AHA definition used in prior pediatric metabolic syndrome studies (pediatric AHA), and the International Diabetes Federation (IDF) guidelines. We found that factor structures were essentially identical at both time points. However, clinical categorization was not stable. Approximately half of adolescents with baseline metabolic syndrome lost the diagnosis at follow-up regardless of the definitions used: pediatric AHA=56% (95% confidence interval [CI], 42% to 69%), AHA=49% (95% CI, 32% to 66%), IDF=53% (95% CI, 38% to 68%). In addition to loss of the diagnosis, new cases were identified. Cumulative incidence rates were as follows: pediatric AHA=3.8% (95% CI, 2.8% to 5.2%); AHA=4.4% (95% CI, 3.3% to 5.9%); IDF=5.2% (95% CI, 4.0% to 6.8%).

CONCLUSIONS

During adolescence, metabolic risk factor clustering is consistent. However, marked instability exists in the categorical diagnosis of metabolic syndrome. This instability, which includes both gain and loss of the diagnosis, suggests that the syndrome has reduced clinical utility in adolescence and that metabolic syndrome-specific pharmacotherapy for youth may be premature.

Update on the metabolic syndrome in children

PURPOSE OF REVIEW

Provides an update on the metabolic syndrome in childhood.

RECENT FINDINGS

The metabolic syndrome is increasingly recognized among children. It is nearly exclusively encountered in overweight and obese individuals and is associated with atherosclerosis. Development and clustering of cardiovascular risk factors is influenced by many characteristics including heritable traits, prenatal and infantile influences, diet, physical activity, and socioeconomic status.

SUMMARY

Epidemiological data have become mature in this area. Efforts to design and implement systems to prevent and treat the metabolic syndrome are required.

Foetal nutritional status and cardiovascular risk profile among children

OBJECTIVE

To estimate the impact of foetal nutritional status on cardiovascular risk among children with the Foetal Nutritional Status Index (FNSI), calculated by dividing the child's birth weight (BW, kg) by the mother's height (m2).

DESIGN

Cross-sectional survey analysis.

SETTING

A sample of children from the US Third National Health and Nutrition Examination Survey.

SUBJECTS

A total of 3109 children who were 5-11 years of age and had data on BW and mother's height. Non-fasting blood samples were included.

RESULTS

Overall, the FNSI was positively associated with BW and negatively associated with mother's height (P<0.0001). Within sex-specific quintiles of FNSI (third quintile as reference) adjusted for potential confounding variables, cardiovascular risk factors tended to be 'higher' in the lower quintiles for males while the opposite was true for females. Multivariate logistic regression analyses indicated that the odds for males in quintile 1 was 2.4 for having a low level of high-density lipoprotein cholesterol (P<0.01) and 2.1 for having a cluster of cardiovascular risk factors (P=0.01); for females, the odds of having a cluster of cardiovascular risk factors was approximately two times higher for those in the first and fifth quintiles, who also had a significantly higher prevalence of central obesity.

CONCLUSIONS

The FNSI may be a potential proxy indicator of foetal nutritional status and it may be used to test specific hypotheses of whether foetal nutrition restriction or overnutrition programmes future cardiovascular risk.

Factor analysis of risk variables associated with metabolic syndrome in Asian Indian adolescents

The purpose of the present cross-sectional study was to identify components of risk variables associated with metabolic syndrome in Asian Indian adolescents. The sample included 400 adolescents (boys = 200; mean age, 15.0 +/- 4.5 years; girls = 200; mean age, 14.4 +/- 3.8 years) from Calcutta, India. The following variables were considered: body mass index, waist circumference, sum of four skinfolds, subscapular/triceps ratio, total cholesterol, triglycerides, blood glucose, and systolic, diastolic, and mean arterial pressure. Principal component factor analysis revealed four uncorrelated factors for adolescent boys that cumulatively explained 76.3% of the observed variance of metabolic syndrome. Four factors with overlap between factors 1 and 2 were observed for adolescent girls that cumulatively explained 74.3% of the total variation of metabolic syndrome. The four factors identified were central body fat distribution (factor 1), centralized subcutaneous fat (factor 2), lipids-blood glucose (factor 3), and blood pressure (factor 4). Furthermore, the first two factors, i.e., central body fat distribution and centralized subcutaneous fat, cumulatively explained more than 46% (46.5% for boys; 46.4% for girls) of the observed variation of metabolic syndrome. Since more than one factor was identified for metabolic syndrome, more than one physiological mechanism could account for the clustering of risk variables of metabolic syndrome in Asian Indian adolescents. Factor analysis of Asian Indian adults also revealed four uncorrelated factors, similar to the present factors, therefore warranting intervention as early as adolescence.

OBESITY IN CHILDHOOD AND CARDIOVASCULAR RISK

1. Childhood obesity is increasing worldwide and is associated with an increase in cardiovascular risk factors in childhood. 2. In children, obesity is associated with hypertension, impaired vascular function, dyslipidaemia, atheroma, the metabolic syndrome, type 2 diabetes, systemic inflammation and oxidative stress. Greater risk is associated with clustering of risk factors. 3. Obesity tracks from childhood to adult life and predicts adverse levels of risk and an increase in cardiovascular end-points. 4. Adults who were obese as children have higher rates of obesity and its sequelae: greater intima-media thickness, left ventricular hypertrophy and atherosclerosis. There is greater all-cause and cardiovascular mortality, as well as a greater risk of stroke, in long-term follow-up of obese children. 5. Genetic and environmental factors contribute to familial aggregation of obesity, with parental obesity as a strong predictor of obesity in children. However, clustering of adverse health-related behaviours is seen in such families. 6. Adverse behaviours (smoking, poor dietary choices, less physical activity and greater alcohol intake) also cluster in individuals, suggesting the need for multimodal interventions. 7. Recognition of families at risk offers opportunities for prevention of obesity in children and decreasing risk in parents.

Perinatal and childhood origins of cardiovascular disease

BACKGROUND

Features of the metabolic syndrome comprise a major risk for cardiovascular disease and will increase in prevalence with rising childhood obesity. We sought to identify early life influences on development of obesity, hypertension and dyslipidemia in children.

METHODS AND RESULTS

Cluster analysis was used on a subset of a longitudinal Australian birth cohort who had blood samples at age 8 (n=406). A quarter of these 8-year-olds fell into a cluster with higher body mass index, blood pressure (BP), more adverse lipid profile and a trend to higher serum glucose resembling adult metabolic syndrome. There was a U-shaped relationship between percentage of expected birth weight (PEBW) and likelihood of being in the high-risk cluster. The high-risk cluster had elevated BP and weight as early as 1 and 3 years old. Increased likelihood of the high-risk cluster group occurred with greatest weight gain from 1 to 8 years old (odds ratio (OR)=1.4, 95% confidence interval (CI)=1.3-1.5/kg) and if mothers smoked during pregnancy (OR=1.82, CI=1.05-3.2). Risk was lower if children were breast fed for >/=4 months (OR=0.6, 95% CI=0.37-0.97). Newborns in the upper two quintiles for PEBW born to mothers who smoked throughout pregnancy were at greatest risk (OR=14.0, 95% CI=3.8-51.1) compared to the nadir PEBW quintile of non-smokers.

CONCLUSION

A U-shaped relationship between birth weight and several components of the metabolic syndrome was confirmed in a contemporary, well-nourished Western population of full-term newborns, but post-natal weight gain was the dominant factor associated with the high-risk cluster. There was a prominence of higher as well as lowest birth weights in those at risk. Future health programs should focus on both pre- and post-natal factors (reducing excess childhood weight gain and smoking during pregnancy), and possibly the greatest benefits may arise from targeting the heaviest, as well as lightest newborns, especially with a history of maternal smoking during pregnancy.