Insulin Resistance and Clustering of Cardiometabolic Risk Factors in Urban Teenagers in Southern India AMBADY RAMACHANDRAN, DSC 1 CHAMUKUTTAN SNEHALATHA, DSC 1 ANNASAMI YAMUNA, PHD 1 NARAYANASAMY MURUGESAN, PHD 1 K.M. VENKAT NARAYAN, MD 2 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 circum- ference 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. Diabetes Care 30:1828–1833, 2007 I nsulin resistance is associated with obesity, type 2 diabetes, cardiovascular disease, and subclinical cardiometa- bolic risk markers, such as dyslipidemia, hypertension, and central adiposity (1,2). In fact, many have hypothesized that in- sulin resistance may be the common pathophysiological factor tying together a “syndrome” of cardiometabolic distur- bance, affecting adiposity, glucose intol- erance, dyslipidemia, and altered blood pressure control (2– 4). On the other hand, the concept that such a syndrome exists has recently been challenged (5). The association between insulin resis- tance and cardiometabolic risk factors is often confounded once the disease sets in. The ideal population for examining these associations in depth would be one that is: 1) at high risk of insulin resistance, 2) young and has not yet acquired clinical disease, and 3) undergoing rapid environ- mental and lifestyle change. Asian Indians are at high risk of type 2 diabetes and cardiovascular disease and have an insulin-resistant phenotype, characterized by low muscle mass, upper- body adiposity, and high percentage of body fat (6,7). While insulin resistance runs in families and may have a genetic basis (8), it is often lifestyle factors that trigger the cardiometabolic disease pro- cesses (9). With India undergoing rapid industrialization and urbanization, the consequent changes in the form of seden- tary lifestyle are rampant (10,11). In this study, among young and healthy adolescents (aged 12–19 years) from urban southern India, we examined the following: 1) the occurrence of cardio- metabolic risk variables; 2) the distribution of insulin resistance and its association with the individual cardiometabolic risk vari- ables, which included blood pressure, se- rum triglycerides, fasting plasma glucose, and HDL cholesterol; and 3) how cardio- metabolic risk factors cluster and how much of such clustering may be associ- ated with insulin resistance. In the con- text of the rising prevalence of overweight and diabetes in India (11,12), especially at a younger age, these data will also serve toward policy formulation for preventive strategies. RESEARCH DESIGN AND METHODS — A school-based, cross- sectional survey was done among 2,640 children (1,323 boys and 1,317 girls) aged 12–19 years studying in 8th to 12th standards in 16 schools in Chennai, India. The schools were selected from different regions in the city and covered govern- ment and private schools attended by children across all socioeconomic groups. Adolescents aged 19 years (n = 16) were grouped with those aged 18 years. All subjects from each class were selected, and the response rate was 92%. Signed informed consent was given by parents. The ethics committee of the institution approved the protocol. Details of demography, medical his- tory, parental income, and family history ●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●● From the 1 Diabetes Research Centre, M.V. Hospital for Diabetes, World Health Organization Collaborating Centre for Research, Education, and Training in Diabetes, Royapuram, Chennai, India; and the 2 Hubert Department of Global Health, Rollins School of Public Health, Emory University, Atlanta, Georgia. Address correspondence and reprint requests to Dr. A. Ramachandran, MD, PhD, India Diabetes Research Foundation, 28 Marshalls Rd., Egmore, Chennai 600008, India. E-mail: ramachandran@vsnl.com. Received for publication 13 October 2006 and accepted in revised form 19 March 2007. Published ahead of print at http://care.diabetesjournals.org on 6 April 2007. DOI: 10.2337/dc06-2097. Abbreviations: HOMA-IR, homeostasis model assessment of insulin resistance. A table elsewhere in this issue shows conventional and Syste `me International (SI) units and conversion factors for many substances. © 2007 by the American Diabetes Association. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact. Cardiovascular and Metabolic Risk O R I G I N A L A R T I C L E 1828 DIABETES CARE, VOLUME 30, NUMBER 7, JULY 2007