|Year : 2015 | Volume
| Issue : 3 | Page : 140-146
Central adiposity indicators for assessing risk of high blood pressure among Indian adolescents
Priti Apte, Shobha Rao
Department of Biometry and Nutrition Unit, Agharkar Research Institute, Pune, Maharashtra, India
|Date of Submission||16-Jan-2015|
|Date of Decision||07-Mar-2015|
|Date of Acceptance||02-Jun-2015|
|Date of Web Publication||6-Aug-2015|
Biometry and Nutrition Unit, Agharkar Research Institute, Pune - 411 004, Maharashtra
Source of Support: None, Conflict of Interest: None
Introduction: In adults, central adiposity is known to be an indicator of intra-abdominal fat and correlates directly with cardiovascular disease risk. However, it is unclear whether central adiposity predicts similar risks among adolescents. Objective: The objective was to study the clinical validity of central adiposity indicators for predicting the risk of high blood pressure (BP) among Indian adolescents. Subjects and Methods: Children from 5 th to 10 th standard covering age group of 9-15 years (boys = 490 and girls = 468) were included in the study. Anthropometric measurements such as weight, height, body fat %; the skin fold thickness at four sites and waist circumference were measured by trained investigators using standard procedures. BP was measured using sphygmomanometer by a qualified pediatrician. Results: Overall adiposity and central adiposity correlated significantly with systolic blood pressure (SBP) and diastolic blood pressure (DBP). Mean SBP and DBP was remarkably higher among overweight subjects. Similarly, the prevalence of high BP was higher among overweight subjects. Prevalence of high BP showed an increasing trend from lower to higher tertile of waist circumference and subscapular skinfold. Sub-scapular skin folds (for boys) and waist circumference (for girls) showed significant odds ratio even in the middle tertile indicating early prediction for high SBP. Conclusion: The data suggest that subscapular skinfolds and waist circumference was a better and early indicator for identifying the risk of high BP in boys and girls, respectively. The above study thus needs to be tested on a larger sample.
Keywords: Central adiposity, diastolic blood pressure, Indian adolescents, subscapular skinfolds, systolic blood pressure, waist circumference
|How to cite this article:|
Apte P, Rao S. Central adiposity indicators for assessing risk of high blood pressure among Indian adolescents. J Obes Metab Res 2015;2:140-6
| Introduction|| |
Obesity is a major public health problem in developed countries and in some parts of developing countries. It's a growing concern in countries like India, who are witnessing the nutritional transition.  Obesity in adults is known to be a major risk factor for coronary heart disease (CHD). Like obesity in adults, adolescent obesity too has important health consequences and is known to be a major antecedent of adult obesity.  Persistence of adolescent obesity into adulthood has been shown by several studies. ,, Guo et al. have reported that overweight during childhood especially beyond 8 years, are an important risk factor for overweight at the age of 35 years. 
Adiposity is known to be positively associated with blood pressure (BP) and other cardiovascular disease in children and adolescents. Recent studies showed that a greater deposition of central fat is correlated with less favorable patterns of BP and serum lipoprotein concentrations.  A pattern of excess fat in the central region (truncal fat) is known to be associated with increased cardiovascular risks, such as elevated BP.  Recently, fat distribution has been identified to be more important than total body fat assessment.  This is particularly true among Asians who have a higher trunk to peripheral fat ratio. 
In adults, simple anthropometric measures of central adiposity such as measurement of the subcutaneous layer of fat at sub-scapular, supra-illiac, and waist circumference are known to correlate with increased cardiovascular risk. Until recently, hypertension was considered a rare condition in adolescence. Various studies from different populations among adults have reported that obesity is a major risk factor for hypertension. However, studies examining this association among adolescents are scarce. It is unclear whether these indicators predict similar risks among adolescents. Hence, it was important to study health consequences of obesity among adolescents in India, especially when the prevalence of obesity is on the rise. The use of simple indicators such as waist circumference, subscapular skinfolds thickness, and supra-iliac skin fold thickness needs to be explored among adolescents. Therefore, we studied the clinical validity of these adiposity indicators for predicting the risk of high BP among Indian adolescents.
| Subjects and methods|| |
School going children from 5 th to the 10 th standard between the age-group of 9 and 15 years (boys = 490 and girls = 468), belonging to the middle class were included in the study. Absentees (7.6% boys and 8.6% girls) on the days of the survey were the only exclusions. Age assessment was done using birth date records from the school. The study was conducted after seeking the consent of the parents of children and taking approval of the Institutional Research Advisory Committee.
Anthropometric measurements were recorded in duplicate by trained investigators using standard procedures. Nevertheless, an interobserver variability study was done before starting the study. Among the investigators, the variation was negligible for the measurements, which were taken with the help of digital equipment's viz-a-viz weighing scale and body composition analyzer. Weight was recorded (up to 20 g) using electronic weighing balance (Suysan, India); height was measured by a stadiometer (up to 0.1 cm). Body mass index (BMI) was calculated as a ratio of weight (kg) to the square of height (m 2 ). Body fat percent was measured using Omran (HBF 300, Japan) equipment that works on the principle of bioelectrical impedance analysis. Subcutaneous fat is known as a storehouse of the energy reserve of the body. The thickness of fat at various sites is found to be correlated with body fat measurement as determined by the autopsy, densitometry, and radiography. Skin fold thickness may be measured on different sites like sub-scapular, supra iliac that represents central adiposity or at extremities, that is, triceps and biceps that represents peripheral obesity. Therefore, skinfold thicknesses were measured on the left side of the body in duplicate at four sites, that is, triceps, biceps, suprailiac, and subscapular to the nearest of 0.2 mm with a Harpenden's skin fold caliper (CMS Instruments, London, UK). Waist circumference was measured using a nonstretchable measuring tape with an accuracy of 0.1 cm.
A pediatrician who accompanied the team measured the BP using mercury sphygmomanometer. The subject was asked to rest for 10 min prior to the BP measurement. Measurements were taken in duplicates in seated position. The subject was advised to remain still, calm, and quiet during the measurement.
Definition for overweight and high blood pressure
Body mass index
Body mass index, a conventional indicator, was used to assess the prevalence of overweight.  The cut-offs given by International Obesity Task Force (IOTF), which are linked to the widely accepted adult cut-off points of BMI >25 kg/m 2 were used.
Body fat percent
Although, BMI is widely used as a surrogate measure of adiposity, it is a measure of excess weight relative to height rather than excess body fat. Therefore, we computed the prevalence of overweight using body fat cuts-offs also. Cut off (body fat ≥25% for boys and ≥30% for girls) defined by Williams et al. were used. 
Skin-fold at triceps
For triceps indicator, the 85 th percentile age-sex values given by Must et al. were used. 
Assessment of high systolic or high diastolic blood pressure
We defined high systolic blood pressure (HSBP) and high diastolic blood pressure (HDBP) independently when measured systolic blood pressure (SBP) or diastolic blood pressure (DBP) was above or equal to 95 th percentile of SBP or DBP for age, sex, and height percentile. 
| Results|| |
Adolescence represents a period of rapid physical growth and development causing a significant increase in height, weight, as well as changes, in body composition. Therefore, age-wise means of anthropometric parameters were studied [Figure 1]. Weight and BMI showed an increasing trend with age in both sexes. In case of body fat percent and triceps, an increasing trend with age among girls was seen, but no such trend was observed among boys. Mean body fat and triceps skin-fold thickness for girls were higher than that for boys in most age groups, and the difference widened beyond 12 years of age. Indicators of central obesity such as waist circumference and subscapular skinfold were also examined and are plotted in [Figure 2]. Waist circumference and subscapular skin-fold showed an increasing trend with age in both the sexes. Mean subscapular skin-fold was significantly higher among girls than boys across all ages.
|Figure 1. Mean values of weight, body mass index, body fat, and triceps by age groups for boys and girls|
Click here to view
|Figure 2. Mean waist circumference and subscapular skinfold thickness among adolescent boys and girls|
Click here to view
Assessment of overweight was done using three different indicators. First, BMI a conventional indicator was considered.  Second, body fat percent, which measures the overall adiposity, was used. Finally, the skin fold thickness at triceps was used for measurement of subcutaneous fat. Prevalence of overweight using different indicators for three stages of adolescence, separately for boys and girls is given in [Table 1]. Prevalence of overweight assessed by either indicator was higher among boys than that in girls. The prevalence of overweight among boys and girls was 14.3% and 13.8%, respectively using BMI (IOTF) cut-offs. The prevalence of HSBP and HDBP using 95 th percentile age-sex specific cut-offs given in the fourth report on the diagnosis, evaluation, and treatment of high BP in children and adolescents was 13.1% and 19.6%, respectively, among boys and 16.5% and 25.3%, respectively, among girls [Table 1].
|Table 1: Prevalence (%) of OW and high BP among adolescent using various indicators |
Click here to view
Simple correlation between SBP and DBP with indicators of adiposity (BMI, body fat, and triceps) [Table 2] revealed that all measures of adiposity were positively and significantly associated with SBP, as well as DBP in both the sexes. However, the magnitude of the correlation between adiposity indicators and BP differed considerably and was higher for SBP than that for DBP. BMI showed highest correlation with SBP (r = 0.394 for boys and r = 0.283 for girls) and DBP (r = 0.283 for boys and r = 0.271 for girls). In view of the positive association between adiposity and BP levels, we compared the BP levels and prevalence of HSBP and HDBP among overweight and nonoverweight subjects [Table 3]. Mean SBP and DBP levels were significantly (P < 0.01) higher among overweight subjects as compared to nonoverweight subjects. Mean SBP and DBP were higher by at least 5 mmHg and 3 mmHg, respectively among overweight subjects (using any indicator) in both the sexes. Prevalence of HSBP and HDBP was also significantly higher among overweight subjects as compared to their counterparts.
|Table 2: Correlation coefficient values of SBP/DBP with adiposity indicators |
Click here to view
|Table 3: Prevalence of HSBP/HDBP and mean SBP/DBP among OW and their age-sex matched controls |
Click here to view
Since age related increase was seen in all adiposity indicator age adjustment tertiles of these indicators were computed, and mean values of observed SBP and DBP were compared for age-adjusted tertiles [Table 4]. Mean levels of SBP and DBP increased significantly from lower to higher tertile of all three indicators of adiposity. Similarly, the prevalence of HSBP and HDBP also showed an increasing trend from lower to higher tertile of all these indicators in both the sexes [Figure 3]. Consequently, the odds ratio (OR) for risk of HSBP and HDBP [Table 5] showed that the risk was significantly higher among subjects in the highest tertile of these indicators.
|Figure 3. Prevalence of high systolic blood pressure/high diastolic blood pressure among adolescents by tertiles of adiposity indicators|
Click here to view
|Table 4: Mean (±SD) SBP and DBP by age adjusted tertiles of adiposity indicators |
Click here to view
|Table 5: OR's (95th % CI) for HSBP and HDBP by age adjusted tertiles of indicators of adiposity |
Click here to view
Finally, we studied the association of central obesity indicators with BP. For this, simple correlation between indicators of central adiposity, that is, waist circumference and subscapular skin folds with SBP and DBP were computed separately for boys and girls. Both indicators showed significant correlations with SBP and DBP. Overall the magnitude of the correlation was higher for waist circumference than that for subscapular skin fold in both sexes. Further, especially among boys, both the indicators showed a higher correlation with SBP than that with DBP. Mean levels of SBP and DBP were significantly (P < 0.01) higher among subjects in the higher tertile of waist circumference and subscapular skin fold. Prevalence of HSBP and HDBP also showed an increasing trend from lower to higher tertile of these two indicators, in both the sexes [Table 4].
Further to identify the risk of high BP, OR for HSBP, and HDBP were computed using lower tertile of these indicators as reference category [Table 5]. Among boys, waist circumference did not show significant OR's for HSBP but tertiles for Sub-scapular skin folds do reflect increasing risk of HSBP. In contrast, among girls it is waist circumference that showed significant OR's, but subscapular skin fold failed to show significant risk. In fact, both subscapular skin folds (for boys) and waist circumference (for girls) showed significant OR's even in the middle tertile indicating early prediction for HSBP. This data suggest that among boys subscapular skin folds was a better indicator for identifying the risk of high BP, while, among girls, waist circumference was a better indicator for predicting the risk of high BP. The middle tertile of subscapular skin folds corresponds to 6.13 mm for boys and 8.59 mm for girls while the middle tertile of waist circumference corresponds to 58.42 cm for boys and 57.60 cm for girls. Thus, these results suggest that both waist circumference, as well as sub-scapular skin folds, can identify the risk of high BP among adolescents. However, subscapular skin folds was a better indicator for identifying the risk of high BP among boys while among girls waist circumference was a better indicator and needs to be tested on a large scale study.
| Discussion|| |
Mean body fat (percent) and triceps skinfolds for girls were higher than that for boys. This is due to greater built of muscle and bone mass in boys and higher body fat in girls during adolescence.  Prevalence of overweight assessed by either indicator was higher among boys than in girls. The prevalence of overweight among boys and girls was 14.3% and 13.8%, respectively using BMI (IOTF) cut-offs and was in confirmation with other studies from India. , The prevalence of HSBP and HDBP was 13.1% and 19.6%, respectively, among boys and 16.5% and 25.3%, respectively, among girls. Among boys, the prevalence of HSBP, as well as HDBP, showed a decreasing trend (though not statistically significant) as age advanced, however, no such trend was observed among girls. This could probably be again related to the greater gains in muscle and bone experienced by boys. Prevalence of HSBP and HDBP among overweight subjects was 20.0% and 28.6%, respectively, for boys, 30.3% and 43.9%, respectively, for girls. The exact mechanism how adiposity leads to increased risk of high BP is controversial, however three main physiological mechanisms, that is, disturbances in autonomic function, insulin resistance, and abnormalities in vascular structure and function are suspected to be the causes. 
Waist circumference and subscapular skinfold showed a higher correlation with SBP than that with DBP. A cross-sectional analysis of children aged 8-17 years from France reported similar results, where the correlation between SBP and waist circumference was higher than the correlation between DBP and waist circumference. Botton et al. reported that it was SBP, which is associated with both total fat and its distribution, whereas DBP is associated only with total body fat percent. Mean levels of SBP and DBP were significantly (P < 0.01) higher among subjects in the higher tertile of waist circumference and subscapular skin fold.  Shear et al. studied young adults (5 years 24 years) from Bogalusa, Louisiana, where mean SBP change of 6.9 mmHg from the lowest to highest quartile of the subscapular skin fold.  Prevalence of HSBP and HDBP also showed an increasing trend from lower to higher tertile of these two indicators, in both the sexes. Hirschler et al. studied association between waist circumference and BP among 84 students aged 6-13 years, where approximately 51% of the children with higher waist circumference had at least one risk factor for CHD, such as elevated BP, hyperlipidemia, or insulin resistance compared to 28% in the group with lower waist circumference. 
Among boys, sub-scapular skin folds was a better indicator for identifying the risk of high BP while, among girls, waist circumference was a better indicator for predicting the risk of high BP. He et al. reported similar sex difference when the association between BP and measures of central adiposity was studied among 920 healthy subjects aged between 5 and 18 years from African-American, Asian, and Caucasian. He et al. reported that trunk fat measured by subscapular skin folds was significantly and positively associated with BP only among boys.  On the other hand, Folsom et al. reported that among adults a significant and independent association between fat distribution (assessed by waist/hip ratio) and BP was seen in women. 
| Conclusion|| |
Fat distribution appears to have more significant influence on cardiovascular risk factors in adolescents than overall adiposity. We found that central adiposity was a better predictor of HSBP as well as HDBP. However, the association between central adiposity is stronger with HSBP among adolescents. Further, among girls waist circumference is a better indicator while among boys subscapular skinfold thickness is a better indicator for assessing the risk of high BP. Thus, routine measurement of waist circumference and subscapular skinfold thickness can be important useful for screening adolescents at risk of high BP.
Financial support and sponsorship
Conflict of interest
There are no conflict of interest.
| References|| |
Popkin BM. The nutrition transition and obesity in the developing world. J Nutr 2001;131:871S-3.
Popkin BM, Udry JR. Adolescent obesity increases significantly in second and third generation U.S. immigrants: The National Longitudinal Study of Adolescent Health. J Nutr 1998;128:701-6.
Rolland-Cachera MF, Deheeger M, Guilloud-Bataille M, Avons P, Patois E, Sempé M. Tracking the development of adiposity from one month of age to adulthood. Ann Hum Biol 1987;14:219-29.
Siervogel RM, Roche AF, Guo SM, Mukherjee D, Chumlea WC. Patterns of change in weight/stature2 from 2 to 18 years: Findings from long-term serial data for children in the Fels longitudinal growth study. Int J Obes 1991;15:479-85.
Serdula MK, Ivery D, Coates RJ, Freedman DS, Williamson DF, Byers T. Do obese children become obese adults? A review of the literature. Prev Med 1993;22:167-77.
Guo SS, Roche AF, Chumlea WC, Gardner JD, Siervogel RM. The predictive value of childhood body mass index values for overweight at age 35 y. Am J Clin Nutr 1994;59:810-9.
Shear CL, Freedman DS, Burke GL, Harsha DW, Berenson GS. Body fat patterning and blood pressure in children and young adults. The Bogalusa Heart Study. Hypertension 1987;9:236-44.
He Q, Horlick M, Fedun B, Wang J, Pierson RN Jr, Heshka S, et al. Trunk fat and blood pressure in children through puberty. Circulation 2002;105:1093-8.
Sardinha LB, Teixeira PJ, Guedes DP, Going SB, Lohman TG. Subcutaneous central fat is associated with cardiovascular risk factors in men independently of total fatness and fitness. Metabolism 2000;49:1379-85.
Misra A. Revisions of cutoffs of body mass index to define overweight and obesity are needed for the Asian-ethnic groups. Int J Obes Relat Metab Disord 2003;27:1294-6.
Cole TJ, Bellizzi MC, Flegal KM, Dietz WH. Establishing a standard definition for child overweight and obesity worldwide: International survey. BMJ 2000;320:1240-3.
Williams DP, Going SB, Lohman TG, Harsha DW, Srinivasan SR, Webber LS, et al. Body fatness and risk for elevated blood pressure, total cholesterol, and serum lipoprotein ratios in children and adolescents. Am J Public Health 1992;82:358-63.
Must A, Dallal GE, Dietz WH. Reference data for obesity: 85 th
and 95 th
percentiles of body mass index (wt/ht2) and triceps skinfold thickness. Am J Clin Nutr 1991;53:839-46.
National High Blood Pressure Education Program. Update on the Task Force Report of High Blood Pressure in Children and Adolescents. (September 1996): Washington, DC: US Government Printing Office; National Institute of Health Publication No. 96-3790; 1987. p. 1-24.
Ramachandran A, Snehalatha C, Vinitha R, Thayyil M, Kumar CK, Sheeba L, et al. Prevalence of overweight in urban Indian adolescent school children. Diabetes Res Clin Pract 2002;57:185-90.
Rao S, Apte P. Social class-related gradient in the association of skeletal growth with blood pressure among adolescent boys in India. Public Health Nutr 2009;12:2256-62.
Sorof J, Daniels S. Obesity hypertension in children: A problem of epidemic proportions. Hypertension 2002;40:441-7.
Botton J, Heude B, Kettaneh A, Borys JM, Lommez A, Bresson JL, et al. Cardiovascular risk factor levels and their relationships with overweight and fat distribution in children: The Fleurbaix Laventie Ville Santé II study. Metabolism 2007;56:614-22.
Hirschler V, Aranda C, Calcagno Mde L, Maccalini G, Jadzinsky M. Can waist circumference identify children with the metabolic syndrome? Arch Pediatr Adolesc Med 2005;159:740-4.
He Q, Ding ZY, Fong DY, Karlberg J. Blood pressure is associated with body mass index in both normal and obese children. Hypertension 2000;36:165-70.
Folsom AR, Li Y, Rao X, Cen R, Zhang K, Liu X, et al. Body mass, fat distribution and cardiovascular risk factors in a lean population of south China. J Clin Epidemiol 1994;47:173-81.
[Figure 1], [Figure 2]
[Figure 3], [Table 1], [Table 2], [Table 3], [Table 4], [Table 5]