ABSTRACT:

Objective:

To determine the predictive power of body mass index (BMI), waist circumference (WC), and waist-to-height ratio (WHtR), and their respective cut-off points for high blood pressure (BP) screening in Brazilian children and adolescents.

Method:

Cross-sectional study conducted with 1,139 students aged 6 to 17years. Body weight, height, WC, and BP were measured. High BP was classified as systolic or diastolic ≥ 95^th percentile. Receiver Operating Characteristic (ROC) curves were constructed, and the area under the curve, sensitivity, and specificity were calculated.

Results:

The prevalence of high BP was 27.0%. Anthropometric indices showed a significant association with high BP (accuracy ranging from 0.62 - 0.81), except for WHtR among male adolescents.Sensitivity was low, regardless of the anthropometric index, gender, and age group.

Conclusion:

BMI, WC, and WHtR were associated with high BP, but the cut-off points tested showed low sensitivity. Determining specific cut-off points for each population can enable the use of anthropometric indices in high BP screening.

Keywords:
Arterial pressure; Obesity; Body mass index; Waist circumference; Child

INTRODUCTION

High blood pressure (BP) is considered the main individual risk factor for disease burden and overall mortality. In 2013, estimates indicated that this condition was responsible for 10.4million deaths and more than 8% of disability-adjusted years of life lost¹1. Collaborators GBDRF, Forouzanfar MH, Alexander L, Anderson HR, Bachman VF, Biryukov S, etal. Global, regional, and national comparative risk assessment of 79 behavioural, environmental and occupational, and metabolic risks or clusters of risks in 188 countries, 1990-2013: a systematic analysis for the Global Burden of Disease Study 2013. Lancet 2015; 386(10010): 2287-323. https://doi.org/10.1016/S0140-6736(15)00128-2
https://doi.org/10.1016/S0140-6736(15)00... . Considering the significant prevalence rates of high BP among children and adolescents²2. Christofaro DGD, Andrade SM, Fernandes RA, Cabrera MAS, Ritti-Dias RM. Prevalência de pressão arterial elevada em crianças e adolescentes: revisão sistemática. Rev Bras Saúde Mater Infant 2011; 11(4): 361-7. http://dx.doi.org/10.1590/S1519-38292011000400002
http://dx.doi.org/10.1590/S1519-38292011... ^,33. Magliano ES, Guedes LG, Coutinho ES, Bloch KV. Prevalence of arterial hypertension among Brazilian adolescents: systematic review and meta-analysis. BMC Public Health 2013; 13: 833. https://doi.org/10.1186/1471-2458-13-833
https://doi.org/10.1186/1471-2458-13-833... and the increased risk of this condition persisting in adulthood⁴4. Bao W, Threefoot SA, Srinivasan SR, Berenson GS. Essential hypertension predicted by tracking of elevated blood pressure from childhood to adulthood: the Bogalusa Heart Study. Am J Hypertens 1995; 8(7): 657-65. https://doi.org/10.1016/0895-7061(95)00116-7
https://doi.org/10.1016/0895-7061(95)001... , efforts for early diagnosis and intervention are necessary.

After the age of three, young people should have their BP measured in every clinical assessment, at least annually, as part of their pediatric primary care⁵5. Sociedade Brasileira de Cardiologia, Sociedade Brasileira de Hipertensão, Sociedade Brasileira de Nefrologia. VI Diretrizes Brasileiras de Hipertensão. Arq Bras Cardiol 2010; 95(1 Supl.): 1-51.. However, in Brazil, BP monitoring in pediatric age groups is still inadequate and does not cover a large proportion of young people, especially those belonging to the less favored social classes⁶6. da Silva MA, Rivera IR, de Souza MG, Carvalho AC. Blood pressure measurement in children and adolescents: guidelines of high blood pressure recommendations and current clinical practice. Arq Bras Cardiol 2007; 88(4): 491-5.. Thereasons for the under-evaluation of BP are little studied, but could be related to the short duration of pediatric appointments, lack of equipment, especially appropriate cuffs for the arm circumference of young people, and the difficulty in interpreting BP values due to their complex classification criterion - based on percentile distribution according to age, gender, and height⁷7. Lima EIC, Rivera IR. Frequência da medida da pressão arterial em crianças em postos de saúde de Maceió [Trabalho de conclusão de curso]. Maceió (AL): Escola de Ciências Médicas da Universidade de Ciências da Saúde do Estado de Alagoas; 2005.^,88. Mourato FA, Lima Filho JL, Mattos SS. Comparison of different screening methods for blood pressure disorders in children and adolescents. J Pediatr (Rio J) 2015; 91(3): 278-83. http://dx.doi.org/10.1016/j.jped.2014.08.008
http://dx.doi.org/10.1016/j.jped.2014.08... .

After recognizing the under-evaluation of BP and the strong association between obesity and high BP in childhood and adolescence⁹9. Kelishadi R, Ardalan G, Gheiratmand R, Adeli K, Delavari A, Majdzadeh R, etal. Paediatric metabolic syndrome and associated anthropometric indices: the CASPIAN Study. Acta Paediatr 2006; 95(12): 1625-34. https://doi.org/10.1080/08035250600750072
https://doi.org/10.1080/0803525060075007... ^,1010. Christofaro DG, Ritti-Dias RM, Fernandes RA, Polito MD, Andrade SM, Cardoso JR, etal. High blood pressure detection in adolescents by clustering overall and abdominal adiposity markers. Arq Bras Cardiol 2011; 96(6): 465-70.^,1111. Burgos MS, Burgos LT, Camargo MD, Franke SI, Prá D, Silva AM, Borges TS,etal. Relationship between anthropometric measures and cardiovascular risk factors in children and adolescents. Arq Bras Cardiol 2013; 101(4): 288-96. https://doi.org/10.5935/abc.20130169
https://doi.org/10.5935/abc.20130169... , the use of anthropometric indices such as body mass index (BMI), waist circumference (WC), and waist-to-height ratio (WHtR) can represent a simple, non-invasive, and low-cost strategy in the screening of young people with increased risk of high BP. The school routine could include the anthropometric assessment, and young people at risk of developing high BP could be referred to family health units for a more detailed clinical evaluation.

Several studies have investigated the power of BMI, WC, and WHtR in predicting high BP in young people, but it is still not clear which of these anthropometric indices would be more suitable for high BP screening⁹9. Kelishadi R, Ardalan G, Gheiratmand R, Adeli K, Delavari A, Majdzadeh R, etal. Paediatric metabolic syndrome and associated anthropometric indices: the CASPIAN Study. Acta Paediatr 2006; 95(12): 1625-34. https://doi.org/10.1080/08035250600750072
https://doi.org/10.1080/0803525060075007... ^,1010. Christofaro DG, Ritti-Dias RM, Fernandes RA, Polito MD, Andrade SM, Cardoso JR, etal. High blood pressure detection in adolescents by clustering overall and abdominal adiposity markers. Arq Bras Cardiol 2011; 96(6): 465-70.^,1212. Rosa ML, Mesquita ET, da Rocha ER, Fonseca VM. Body mass index and waist circumference as markers of arterial hypertension in adolescents. Arq Bras Cardiol 2007; 88(5): 573-8.^,1313. Chiolero A, Paradis G, Maximova K, Burnier M, Bovet P. No use for waist-for-height ratio in addition to body mass index to identify children with elevated blood pressure. Blood Press 2013; 22(1): 17-20. https://doi.org/10.3109/08037051.2012.701376
https://doi.org/10.3109/08037051.2012.70... ^,1414. Papalia T, Greco R, Lofaro D, Mollica A, Roberti R, Bonofiglio R. Anthropometric measures can better predict high blood pressure in adolescents. J Nephrol 2013; 26(5): 899-905. https://doi.org/10.5301/jn.5000235
https://doi.org/10.5301/jn.5000235... ^,1515. Moraes MM, Veiga GV. Acurácia da gordura corporal e do perímetro da cintura para predizer alterações metabólicas de risco cardiovascular em adolescentes. Arq Bras Endocrinol Metabol 2014; 58(4): 341-51. http://dx.doi.org/10.1590/0004-2730000002865
http://dx.doi.org/10.1590/0004-273000000... . In addition, the definition of the BMI, WC, and WHtR classification criterion with better sensitivity and specificity in detecting high BP among young Brazilians remains open, as previous investigations tested few cut-off points of these indices¹⁰10. Christofaro DG, Ritti-Dias RM, Fernandes RA, Polito MD, Andrade SM, Cardoso JR, etal. High blood pressure detection in adolescents by clustering overall and abdominal adiposity markers. Arq Bras Cardiol 2011; 96(6): 465-70.^,1212. Rosa ML, Mesquita ET, da Rocha ER, Fonseca VM. Body mass index and waist circumference as markers of arterial hypertension in adolescents. Arq Bras Cardiol 2007; 88(5): 573-8.^,1515. Moraes MM, Veiga GV. Acurácia da gordura corporal e do perímetro da cintura para predizer alterações metabólicas de risco cardiovascular em adolescentes. Arq Bras Endocrinol Metabol 2014; 58(4): 341-51. http://dx.doi.org/10.1590/0004-2730000002865
http://dx.doi.org/10.1590/0004-273000000... . These gaps are even more evident in children given that a large part of national studies included only adolescents in their sample¹⁰10. Christofaro DG, Ritti-Dias RM, Fernandes RA, Polito MD, Andrade SM, Cardoso JR, etal. High blood pressure detection in adolescents by clustering overall and abdominal adiposity markers. Arq Bras Cardiol 2011; 96(6): 465-70.^,1212. Rosa ML, Mesquita ET, da Rocha ER, Fonseca VM. Body mass index and waist circumference as markers of arterial hypertension in adolescents. Arq Bras Cardiol 2007; 88(5): 573-8.^,1515. Moraes MM, Veiga GV. Acurácia da gordura corporal e do perímetro da cintura para predizer alterações metabólicas de risco cardiovascular em adolescentes. Arq Bras Endocrinol Metabol 2014; 58(4): 341-51. http://dx.doi.org/10.1590/0004-2730000002865
http://dx.doi.org/10.1590/0004-273000000... . Thus, the objective of this study was to:

METHOD

The present study is part of a school-based epidemiological survey developed in Amargosa, Bahia, Northeast region of Brazil, considered a small city, with an estimated population of 34,845 inhabitants in 2012 and human development index (HDI) of 0.625. The study population consisted of public and private school students of both genders, aged 6 to 17 years, attending from 1st to 9th grade of elementary school and from 1st to 3rd grade of high school.

We used an estimated prevalence of 50% (for various outcomes), a confidence level of 95%, and a maximum allowable error of three percentage points to calculate the sample size. The sample size estimated was 971 children and adolescents. We added 20% (n = 194) for possible cases of incomplete data or refusals to participate in data collection. After the loss of 2.2%, the sample analyzed (n = 1,139) had 90% power (β = 10%) and confidence level of 95% (α = 5%) to detect areas under the Receiver Operating Characteristic (ROC) curve equal to or greater than 0.58 as significant.

The sample selection process had two stages, with “school” being the primary sampling unit and “student,” the secondary. The first stage used a cluster sample of schools proportionally stratified by type of school (“urban public,” “rural public,” and “private”). Fiveurban public, five rural public, and one private school were selected, with the estimated sample size for each stratum being proportional to the study population. The second stage selected the students by simple drawing, considering the number of individuals required in each school to compose a sample equivalent to its size. Data were collected from August 2011 to May 2012. All evaluations occurred at school during the morning period. The Research Ethics Committee of Maria Milza College approved the protocol of the present study (process No. 126/2011). The study included only students who voluntarily agreed to participate and whose parents or legal guardian signed the Informed Consent Form authorizing their involvement.

The previously calibrated digital automatic monitor Omron, model HEM-742 INT (Omron Healthcare, Illinois, United States), measured BP levels. Cuffs with an appropriate size to the arm circumference of the children and adolescents assessed were used both to calibrate the monitor and to measure BP levels. The measurement was taken in the right arm at heart level after the student rested for five minutes. High BP was classified as systolic or diastolic ≥ 95^th percentile, and adjusted for gender, age, and height¹⁶16. National High Blood Pressure Education Program Working Group on High Blood Pressure in Children and Adolescents. The fourth report on the diagnosis, evaluation, and treatment of high blood pressure in children and adolescents. Pediatrics 2004; 114(2 Supl. 4th Report): 555-76..

A Plenna (Plenna, São Paulo, Brazil) digital scale, with capacity for 150 kg and resolution of 100 g measured body weight. The scale underwent a calibration test based on the standard weight comparison method with indications of the calibrated instrument, according to the electronic scale procedure, approved following Inmetro Directive No. 236/94¹⁷17. Brasil. Ministério da Indústria, do Comércio e do Turismo.Instituto Nacional de Metrologia, Normalização e Qualidade Industrial. Portaria nº 236. Brasil: Instituto Nacional de Metrologia, Normalização e Qualidade Industrial; 1994.. Height was measured using a Seca portable stadiometer, model Bodymeter 208 (Seca Ltd., Birmingham, United Kingdom), fixed to the wall, graduated from 0 to 220cm, with an accuracy of 0.1cm. Both variables were measured following standardized procedures and techniques¹⁸18. Gordon CC, Chumlea WCC, Roche AF. Stature, recumbent length, and weight. In: Lohman TG, Roche AF, Martorell R, eds. Anthropometric standardization reference manual. Champaign: Human Kinetics; 1988. p. 3-8. and used to calculate BMI [BMI = body weight (kg)/height²2. Christofaro DGD, Andrade SM, Fernandes RA, Cabrera MAS, Ritti-Dias RM. Prevalência de pressão arterial elevada em crianças e adolescentes: revisão sistemática. Rev Bras Saúde Mater Infant 2011; 11(4): 361-7. http://dx.doi.org/10.1590/S1519-38292011000400002
http://dx.doi.org/10.1590/S1519-38292011... (m)]. BMI was classified according to four criteria: International Obesity Task Force (IOTF)¹⁹19. Cole TJ, Bellizzi MC, Flegal KM, Dietz WH. Establishing a standard definition for child overweight and obesity worldwide: international survey. BMJ 2000; 320(7244): 1240-3., World Health Organization (WHO)²⁰20. de Onis M, Onyango AW, Borghi E, Siyam A, Nishida C, Siekmann J. Development of a WHO growth reference for school-aged children and adolescents. Bull World Health Organ 2007; 85(9): 660-7., Centers for Disease Control and Prevention (CDC)²¹21. Kuczmarski RJ, Ogden CL, Guo SS, Grummer-Strawn LM, Flegal KM, Mei Z, etal. 2000 CDC Growth Charts for the United States: methods and development. Vital Health Stat 11 2002; (246): 1-190., and Conde and Monteiro²²22. Conde WL, Monteiro CA. Body mass index cutoff points for evaluation of nutritional status in Brazilian children and adolescents. J Pediatr (Rio J) 2006; 82(4): 266-72. https://doi.org/doi:10.2223/JPED.1502
https://doi.org/doi:10.2223/JPED.1502... . We distributed the students into the groups “normal weight” or “excess weight” (overweight and obesity). WC was measured with an inelastic anthropometric tape (Cescorf, Brazil) with a resolution of 0.1cm, based on procedures described by WHO²³23. World Health Organization. Measuring obesity: classification and distribution of anthropometric data. Copenhagen: World Health Organization; 1988. (Nutr UD, EUR/ICP/NUT 125)., and classified as normal or high according to criteria proposed by Taylor etal.²⁴24. Taylor RW, Jones IE, Williams SM, Goulding A. Evaluation of waist circumference, waist-to-hip ratio, and the conicity index as screening tools for high trunk fat mass, as measured by dual-energy X-ray absorptiometry, in children aged 3-19 y. Am J Clin Nutr 2000; 72(2): 490-5. https://doi.org/10.1093/ajcn/72.2.490
https://doi.org/10.1093/ajcn/72.2.490... , Katzmarzyk etal.²⁵25. Katzmarzyk PT, Srinivasan SR, Chen W, Malina RM, Bouchard C, Berenson GS. Body mass index, waist circumference, and clustering of cardiovascular disease risk factors in a biracial sample of children and adolescents. Pediatrics 2004; 114(2): e198-205., Fernández etal.²⁶26. Fernández JR, Redden DT, Pietrobelli A, Allison DB. Waist circumference percentiles in nationally representative samples of African-American, European-American, and Mexican-American children and adolescents. J Pediatr 2004; 145(4): 439-44. https://doi.org/10.1016/j.jpeds.2004.06.044
https://doi.org/10.1016/j.jpeds.2004.06.... , and CDC²⁷27. Fryar CD, Gu Q, Ogden CL. Anthropometric reference data for children and adults: United States, 2007-2010. Vital Health Stat 11 2012; (252): 1-48.. Due to the lack of consensus over which percentile to use to define abdominal obesity in young people, we adopted both the 75 (75^th) percentile and the 90 (90^th) percentile of the criteria by Fernández etal.²⁶26. Fernández JR, Redden DT, Pietrobelli A, Allison DB. Waist circumference percentiles in nationally representative samples of African-American, European-American, and Mexican-American children and adolescents. J Pediatr 2004; 145(4): 439-44. https://doi.org/10.1016/j.jpeds.2004.06.044
https://doi.org/10.1016/j.jpeds.2004.06.... and CDC²⁷27. Fryar CD, Gu Q, Ogden CL. Anthropometric reference data for children and adults: United States, 2007-2010. Vital Health Stat 11 2012; (252): 1-48., respectively, to classify high WC in the studied sample. We calculated WHtR using height and WC measures. High WHtR was defined according to a cut-off point designed for adults (≥ 0.5)²⁸28. Ashwell M, Hsieh SD. Six reasons why the waist-to-height ratio is a rapid and effective global indicator for health risks of obesity and how its use could simplify the international public health message on obesity. Int J Food Sci Nutr 2005; 56(5): 303-7. https://doi.org/10.1080/09637480500195066
https://doi.org/10.1080/0963748050019506... and the specific cut-off points for children and adolescents suggested by Kelishadi etal.⁹9. Kelishadi R, Ardalan G, Gheiratmand R, Adeli K, Delavari A, Majdzadeh R, etal. Paediatric metabolic syndrome and associated anthropometric indices: the CASPIAN Study. Acta Paediatr 2006; 95(12): 1625-34. https://doi.org/10.1080/08035250600750072
https://doi.org/10.1080/0803525060075007... and Zhou etal.²⁹29. Zhou D, Yang M, Yuan ZP, Zhang DD, Liang L, Wang CL, etal. Waist-to-Height Ratio: a simple, effective and practical screening tool for childhood obesity and metabolic syndrome. Prev Med 2014; 67: 35-40. https://doi.org/10.1016/j.ypmed.2014.06.025
https://doi.org/10.1016/j.ypmed.2014.06.... .

The descriptive data analysis used mean, median, standard deviation, percentiles, and frequency. The Mann-Whitney test verified the differences between genders (male versus female) and age groups (children = 6 - 9 years versus adolescents = 10 - 17 years) for systolic and diastolic BP, BMI, WC, and WHtR (p < 0.05). The predictive power of BMI, WC, and WHtR for high BP was estimated with ROC curves for each gender in two age groups (children = 6 - 9 years and adolescents = 10 - 17 years). We adopted a confidence interval (CI) of 95%, considering significant areas under the ROC curve whose CI lower limits were ≥ 0.50. The difference in accuracy between anthropometric indices associated with high BP was calculated according to Hanley and McNeil³⁰30. Hanley JA, McNeil BJ. A method of comparing the areas under receiver operating characteristic curves derived from the same cases. Radiology 1983; 148(3): 839-43. https://doi.org/10.1148/radiology.148.3.6878708
https://doi.org/10.1148/radiology.148.3.... . We estimated the sensitivity and specificity of different BMI, WC, and WHtR classification criteria using high BP as an outcome. The software SPSS (version 20.0) and MedCalc (version 9.1.0.1) analyzed the data.

RESULTS

The mean age of the sample was 11.51 years (standard deviation = 3.33). The prevalence of high BP was 27.0% (95%CI 24.5 - 29.6) [male = 24.8% (95%CI 21.2 - 28.6); female = 28.8% (95%CI 25.4 - 32.4); children = 9.4% (95%CI 6.8 - 12.8); adolescents = 35.2% (95%CI 31.9 - 38.6)]. Table 1 shows the differences for BP and anthropometric indices according to gender and age group. Female individuals and adolescents had significantly higher medians for systolic and diastolic BP, BMI, and WC (p < 0.05). WHtR presented higher medians among females and children (p < 0.05).

Anthropometric indices showed a significant association with high BP, except for WHtR among male adolescents (Table 2). For male children, BMI and WC accuracy was significantly greater than WHtR (p = 0.001 and p = 0.002, respectively) (Table 2). Forfemales, the three anthropometric indices investigated had similar accuracy (p>0.05) in both children and adolescents (Table 2).

Obesity prevalence presented a substantial variation with the use of different classification criteria, particularly for WC and WHtR (Table 3). In general, the BMI cut-off points proposed by WHO²⁰20. de Onis M, Onyango AW, Borghi E, Siyam A, Nishida C, Siekmann J. Development of a WHO growth reference for school-aged children and adolescents. Bull World Health Organ 2007; 85(9): 660-7. and Conde and Monteiro²²22. Conde WL, Monteiro CA. Body mass index cutoff points for evaluation of nutritional status in Brazilian children and adolescents. J Pediatr (Rio J) 2006; 82(4): 266-72. https://doi.org/doi:10.2223/JPED.1502
https://doi.org/doi:10.2223/JPED.1502... showed a better balance between sensitivity and specificity in identifying young people with and without high BP. However, regardless of the criterion used to classify BMI, sensitivity was low, especially among adolescents (Table 3). The WC and WHtR cut-off points suggested by Katzmarzyk etal.²⁵25. Katzmarzyk PT, Srinivasan SR, Chen W, Malina RM, Bouchard C, Berenson GS. Body mass index, waist circumference, and clustering of cardiovascular disease risk factors in a biracial sample of children and adolescents. Pediatrics 2004; 114(2): e198-205. and Kelishadi etal.⁹9. Kelishadi R, Ardalan G, Gheiratmand R, Adeli K, Delavari A, Majdzadeh R, etal. Paediatric metabolic syndrome and associated anthropometric indices: the CASPIAN Study. Acta Paediatr 2006; 95(12): 1625-34. https://doi.org/10.1080/08035250600750072
https://doi.org/10.1080/0803525060075007... , respectively, showed a better balance between sensitivity and specificity in identifying young people with and without high BP, except for WHtR among male adolescents, whose cut-off points were not tested (Table 3).

DISCUSSION

The anthropometric indices investigated showed a significant association with high BP, except for WHtR among male adolescents. Nevertheless, testing the cut-off points available in the literature revealed that sensitivity was low, no matter the anthropometric index, gender, and age group used. To increase the chances of early diagnosis and treatment, the applicability of anthropometric indices in the screening of children and adolescents with high BP should prioritize methods with high sensitivity values, consequently, minimizing the number of false-negative results³¹31. Menezes AMB, Santos IS. Curso de epidemiologia básica para pneumologistas. 4ª parte - Epidemiologia clínica. J Pneumologia 1999; 25(6): 321-6. http://dx.doi.org/10.1590/S0102-35861999000600005
http://dx.doi.org/10.1590/S0102-35861999... .

The prevalence of high BP found in the present study was superior to that described for the Brazilian³3. Magliano ES, Guedes LG, Coutinho ES, Bloch KV. Prevalence of arterial hypertension among Brazilian adolescents: systematic review and meta-analysis. BMC Public Health 2013; 13: 833. https://doi.org/10.1186/1471-2458-13-833
https://doi.org/10.1186/1471-2458-13-833... and North-American³²32. May AL, Kuklina EV, Yoon PW. Prevalence of cardiovascular disease risk factors among US adolescents, 1999-2008. Pediatrics 2012; 129(6): 1035-41. https://doi.org/10.1542/peds.2011-1082
https://doi.org/10.1542/peds.2011-1082... pediatric populations. Data from the Bogalusa Heart Study published in 1995 already showed that high BP levels in childhood persist over time and tend to progress to hypertension in adult life⁴4. Bao W, Threefoot SA, Srinivasan SR, Berenson GS. Essential hypertension predicted by tracking of elevated blood pressure from childhood to adulthood: the Bogalusa Heart Study. Am J Hypertens 1995; 8(7): 657-65. https://doi.org/10.1016/0895-7061(95)00116-7
https://doi.org/10.1016/0895-7061(95)001... . Among the young people investigated, 93.3% reported excessive consumption of cold cuts, salted meat, and offal (data not shown). According to information previously published on the sample under study, approximately two-thirds of young people were insufficiently active, increasing by 32% their chances of having high BP; also, those with elevated values for obesity indices were more likely to have high BP³³33. Quadros TM, Gordia AP, Silva LR, Silva DA, Mota J. Inquérito epidemiológico em escolares: determinantes e prevalência de fatores de risco cardiovascular. Cad Saúde Pública 2016; 32(2): e00181514. http://dx.doi.org/10.1590/0102-311X00181514
http://dx.doi.org/10.1590/0102-311X00181... . Another aspect to consider is the fact that the population in the Northeast region still presents worrying indicators of education, occupation, income, housing, sanitation, and access to public health services³⁴34. Instituto Brasileiro de Geografia e Estatística. Síntese de indicadores sociais: uma análise das condições de vida da população brasileira [Internet]. Rio de Janeiro: Instituto Brasileiro de Geografia e Estatística; 2013 [acessado em 24 fev. 2015]. Disponível em: http://biblioteca.ibge.gov.br/visualizacao/livros/liv66777.pdf
http://biblioteca.ibge.gov.br/visualizac... . These factors are determinant of cardiovascular outcomes³⁵35. Soares GP, Brum JD, Oliveira GM, Klein CH, Souza e Silva NA. Evolution of socioeconomic indicators and cardiovascular mortality in three Brazilian states. Arq Bras Cardiol 2013; 100(2): 147-56. and can explain, at least in part, the significant prevalence of high BP in the sample investigated.

Among the anthropometric indices assessed, BMI showed the highest accuracy values to predict high BP, despite being only significantly greater than WHtR among male children. Our findings corroborate previous studies that indicate BMI as a better predictor of high BP compared to other anthropometric indices of cardiovascular risk³⁶36. Chiolero A. Adiposity indicators and blood pressure in children: nothing beyond body mass index? J Hum Hypertens 2015; 29(4): 211-2. http://dx.doi.org/10.1038/jhh.2014.96
http://dx.doi.org/10.1038/jhh.2014.96... ^,3737. Dong B, Wang Z, Wang HJ, Ma J. Associations between adiposity indicators and elevated blood pressure among Chinese children and adolescents. J Hum Hypertens 2015; 29(4): 236-40. https://doi.org/10.1038/jhh.2014.95
https://doi.org/10.1038/jhh.2014.95... . Evidence suggests that obese young people have more chances (between 1.5 and 5 times greater) of developing high BP than non-obese ones¹⁰10. Christofaro DG, Ritti-Dias RM, Fernandes RA, Polito MD, Andrade SM, Cardoso JR, etal. High blood pressure detection in adolescents by clustering overall and abdominal adiposity markers. Arq Bras Cardiol 2011; 96(6): 465-70.^,1212. Rosa ML, Mesquita ET, da Rocha ER, Fonseca VM. Body mass index and waist circumference as markers of arterial hypertension in adolescents. Arq Bras Cardiol 2007; 88(5): 573-8.^,1313. Chiolero A, Paradis G, Maximova K, Burnier M, Bovet P. No use for waist-for-height ratio in addition to body mass index to identify children with elevated blood pressure. Blood Press 2013; 22(1): 17-20. https://doi.org/10.3109/08037051.2012.701376
https://doi.org/10.3109/08037051.2012.70... . Also, in a longitudinal study conducted with 7,203 Chinese children (aged six to eight years), BMI significantly affected the incidence of hypertension³⁸38. Wang J, Zhu Y, Jing J, Chen Y, Mai J, Wong SH, etal. Relationship of BMI to the incidence of hypertension: a 4 years' cohort study among children in Guangzhou, 2007-2011. BMC Public Health 2015; 15: 782. https://dx.doi.org/10.1186%2Fs12889-015-1997-6
https://dx.doi.org/10.1186%2Fs12889-015-... . In addition to its wide use by the scientific community and clinical practice, body weight and height, and consequently BMI, are usually measured in pediatric appointments, Basic Family Health Units, and schools, which can facilitate the high BP screening in childhood and adolescence³⁶36. Chiolero A. Adiposity indicators and blood pressure in children: nothing beyond body mass index? J Hum Hypertens 2015; 29(4): 211-2. http://dx.doi.org/10.1038/jhh.2014.96
http://dx.doi.org/10.1038/jhh.2014.96... .

Comparatively, the BMI cut-off points proposed by WHO²⁰20. de Onis M, Onyango AW, Borghi E, Siyam A, Nishida C, Siekmann J. Development of a WHO growth reference for school-aged children and adolescents. Bull World Health Organ 2007; 85(9): 660-7. and Conde and Monteiro²²22. Conde WL, Monteiro CA. Body mass index cutoff points for evaluation of nutritional status in Brazilian children and adolescents. J Pediatr (Rio J) 2006; 82(4): 266-72. https://doi.org/doi:10.2223/JPED.1502
https://doi.org/doi:10.2223/JPED.1502... showed a better balance between sensitivity and specificity in identifying young people with and without high BP. However, regardless of the criterion used to classify BMI, sensitivity was low. Moraes etal.¹⁵15. Moraes MM, Veiga GV. Acurácia da gordura corporal e do perímetro da cintura para predizer alterações metabólicas de risco cardiovascular em adolescentes. Arq Bras Endocrinol Metabol 2014; 58(4): 341-51. http://dx.doi.org/10.1590/0004-2730000002865
http://dx.doi.org/10.1590/0004-273000000... tested the BMI cut-off points proposed by IOTF¹⁹19. Cole TJ, Bellizzi MC, Flegal KM, Dietz WH. Establishing a standard definition for child overweight and obesity worldwide: international survey. BMJ 2000; 320(7244): 1240-3., CDC²¹21. Kuczmarski RJ, Ogden CL, Guo SS, Grummer-Strawn LM, Flegal KM, Mei Z, etal. 2000 CDC Growth Charts for the United States: methods and development. Vital Health Stat 11 2002; (246): 1-190., and Conde and Monteiro²²22. Conde WL, Monteiro CA. Body mass index cutoff points for evaluation of nutritional status in Brazilian children and adolescents. J Pediatr (Rio J) 2006; 82(4): 266-72. https://doi.org/doi:10.2223/JPED.1502
https://doi.org/doi:10.2223/JPED.1502... to predict high BP in 817 young people aged 6 to 13 years. As in the present study, sensitivity showed low values (31 to 44%), no matter the criterion used, with the Brazilian one being the most sensitive.

WC has been considered one of the main predictors of abdominal fat²⁴24. Taylor RW, Jones IE, Williams SM, Goulding A. Evaluation of waist circumference, waist-to-hip ratio, and the conicity index as screening tools for high trunk fat mass, as measured by dual-energy X-ray absorptiometry, in children aged 3-19 y. Am J Clin Nutr 2000; 72(2): 490-5. https://doi.org/10.1093/ajcn/72.2.490
https://doi.org/10.1093/ajcn/72.2.490... and has a positive correlation with BP in Brazilian children and adolescents¹¹11. Burgos MS, Burgos LT, Camargo MD, Franke SI, Prá D, Silva AM, Borges TS,etal. Relationship between anthropometric measures and cardiovascular risk factors in children and adolescents. Arq Bras Cardiol 2013; 101(4): 288-96. https://doi.org/10.5935/abc.20130169
https://doi.org/10.5935/abc.20130169... . Our study revealed a moderate association between WC and high BP - area under the ROC curve (AUC) ranging from 0.63 to 0.78. However, after testing the cut-off points existing in the literature, we found a wide variation in obesity prevalence and, usually, low sensitivity. As observed in the present investigation, previous studies that compared the ability of WC cut-off points developed with samples of young North-Americans also showed low sensitivity in screening cardiovascular risk factors among the Brazilian pediatric population¹⁰10. Christofaro DG, Ritti-Dias RM, Fernandes RA, Polito MD, Andrade SM, Cardoso JR, etal. High blood pressure detection in adolescents by clustering overall and abdominal adiposity markers. Arq Bras Cardiol 2011; 96(6): 465-70.^,1212. Rosa ML, Mesquita ET, da Rocha ER, Fonseca VM. Body mass index and waist circumference as markers of arterial hypertension in adolescents. Arq Bras Cardiol 2007; 88(5): 573-8.^,3939. Bergmann GG, Gaya A, Halpern R, Bergmann ML, Rech RR, Constanzi CB, etal. Waist circumference as screening instrument for cardiovascular disease risk factors in schoolchildren. J Pediatr (Rio J) 2010; 86(5): 411-6. http://dx.doi.org/10.2223/JPED.2026
http://dx.doi.org/10.2223/JPED.2026... . Inour study, the cut-off points suggested by Katzmarzyk etal.²⁵25. Katzmarzyk PT, Srinivasan SR, Chen W, Malina RM, Bouchard C, Berenson GS. Body mass index, waist circumference, and clustering of cardiovascular disease risk factors in a biracial sample of children and adolescents. Pediatrics 2004; 114(2): e198-205., although less than satisfactory, showed a better balance between sensitivity and specificity in identifying young people with and without high BP in both genders and age groups. Also, the cut-off points based on percentile distribution (CDC²⁷27. Fryar CD, Gu Q, Ogden CL. Anthropometric reference data for children and adults: United States, 2007-2010. Vital Health Stat 11 2012; (252): 1-48. and Fernández etal.²⁶26. Fernández JR, Redden DT, Pietrobelli A, Allison DB. Waist circumference percentiles in nationally representative samples of African-American, European-American, and Mexican-American children and adolescents. J Pediatr 2004; 145(4): 439-44. https://doi.org/10.1016/j.jpeds.2004.06.044
https://doi.org/10.1016/j.jpeds.2004.06.... ) had the worse ability in identifying young people with high BP, which was more evident when testing the 90 percentile. The scarcity of studies with national samples that compared referenced cut-off points for cardiovascular risk factors (for instance, Katzmarzyk etal.²⁵25. Katzmarzyk PT, Srinivasan SR, Chen W, Malina RM, Bouchard C, Berenson GS. Body mass index, waist circumference, and clustering of cardiovascular disease risk factors in a biracial sample of children and adolescents. Pediatrics 2004; 114(2): e198-205.) with referenced cut-off points for percentile distribution (for example, CDC²⁷27. Fryar CD, Gu Q, Ogden CL. Anthropometric reference data for children and adults: United States, 2007-2010. Vital Health Stat 11 2012; (252): 1-48. and Fernández etal.²⁶26. Fernández JR, Redden DT, Pietrobelli A, Allison DB. Waist circumference percentiles in nationally representative samples of African-American, European-American, and Mexican-American children and adolescents. J Pediatr 2004; 145(4): 439-44. https://doi.org/10.1016/j.jpeds.2004.06.044
https://doi.org/10.1016/j.jpeds.2004.06.... ) complicates assessments and prevents the definition of a more accurate classification criterion to detect high BP in young Brazilians.

Out of the three anthropometric indices tested, WHtR showed the worst performance in identifying young people with high BP. In addition to the lack of association with male adolescents, its accuracy was statistically lower than BMI and WC among male children. The ability of WHtR in screening cardiovascular risk factors in young adults is controversial. While some authors suggest that WHtR is the best index of cardiometabolic risk factors for the pediatric population¹⁴14. Papalia T, Greco R, Lofaro D, Mollica A, Roberti R, Bonofiglio R. Anthropometric measures can better predict high blood pressure in adolescents. J Nephrol 2013; 26(5): 899-905. https://doi.org/10.5301/jn.5000235
https://doi.org/10.5301/jn.5000235... ^,4040. Savva SC, Tornaritis M, Savva ME, Kourides Y, Panagi A, Silikiotou N, et al. Waist circumference and waist-to-height ratio are better predictors of cardiovascular disease risk factors in children than body mass index. Int J Obes Relat Metab Disord 2000; 24(11): 1453-8., others advocate that height does not provide any additional advantage to WC, as well as, not improving the accuracy of BMI when added to this index¹³13. Chiolero A, Paradis G, Maximova K, Burnier M, Bovet P. No use for waist-for-height ratio in addition to body mass index to identify children with elevated blood pressure. Blood Press 2013; 22(1): 17-20. https://doi.org/10.3109/08037051.2012.701376
https://doi.org/10.3109/08037051.2012.70... ^,3737. Dong B, Wang Z, Wang HJ, Ma J. Associations between adiposity indicators and elevated blood pressure among Chinese children and adolescents. J Hum Hypertens 2015; 29(4): 236-40. https://doi.org/10.1038/jhh.2014.95
https://doi.org/10.1038/jhh.2014.95... . Our findings demonstrated that the cut-off points for this index suggested by Kelishadi etal.⁹9. Kelishadi R, Ardalan G, Gheiratmand R, Adeli K, Delavari A, Majdzadeh R, etal. Paediatric metabolic syndrome and associated anthropometric indices: the CASPIAN Study. Acta Paediatr 2006; 95(12): 1625-34. https://doi.org/10.1080/08035250600750072
https://doi.org/10.1080/0803525060075007... presented a better balance between sensitivity and specificity in identifying young people with and without high BP in both genders and age groups. The 0.5 cut-off point developed for adults²⁸28. Ashwell M, Hsieh SD. Six reasons why the waist-to-height ratio is a rapid and effective global indicator for health risks of obesity and how its use could simplify the international public health message on obesity. Int J Food Sci Nutr 2005; 56(5): 303-7. https://doi.org/10.1080/09637480500195066
https://doi.org/10.1080/0963748050019506... - and commonly used to classify WHtR in young people¹³13. Chiolero A, Paradis G, Maximova K, Burnier M, Bovet P. No use for waist-for-height ratio in addition to body mass index to identify children with elevated blood pressure. Blood Press 2013; 22(1): 17-20. https://doi.org/10.3109/08037051.2012.701376
https://doi.org/10.3109/08037051.2012.70... ^,1414. Papalia T, Greco R, Lofaro D, Mollica A, Roberti R, Bonofiglio R. Anthropometric measures can better predict high blood pressure in adolescents. J Nephrol 2013; 26(5): 899-905. https://doi.org/10.5301/jn.5000235
https://doi.org/10.5301/jn.5000235... - showed the worst ability in detecting high BP. Motswagole etal.⁴¹41. Motswagole BS, Kruger HS, Faber M, van Rooyen JM, de Ridder JH. The sensitivity of waist-to-height ratio in identifying children with high blood pressure. Cardiovasc J Afr 2011; 22(4): 208-11. https://doi.org/10.5830/CVJA-2010-062
https://doi.org/10.5830/CVJA-2010-062... reported lower sensitivity values for the WHtR 0.5 cut-off point compared to the 0.41 cut-off point for high BP screening in young people and suggested that adopting a value < 0.5 could improve the use of WHtR as a marker of high BP in the pediatric population.

The use of merely statistical critical values for anthropometric indices in the context of screening for risk factors in children and adolescents seems to produce a high number of false-negative results and, consequently, tends to underestimate the prevalence of the disease⁴²42. Quadros TM, Gordia AP, Silva RC, Silva LR. Predictive capacity of anthropometric indicators for dyslipidemia screening in children and adolescents. J Pediatr (Rio J) 2015; 91(5): 455-63. https://doi.org/10.1016/j.jped.2014.11.006
https://doi.org/10.1016/j.jped.2014.11.0... . With respect to the screening for BP changes in the pediatric population, the greater concern is defining cut-off points for anthropometric indices that allow the identification of a larger number of young people with high BP, given that adopting fewer sensitive criteria contributes to delaying the early implementation of measures targeted at the control of BP levels. In addition, cut-off points from high-income countries do not seem to be the most suitable to use in middle- and low-income ones⁴²42. Quadros TM, Gordia AP, Silva RC, Silva LR. Predictive capacity of anthropometric indicators for dyslipidemia screening in children and adolescents. J Pediatr (Rio J) 2015; 91(5): 455-63. https://doi.org/10.1016/j.jped.2014.11.006
https://doi.org/10.1016/j.jped.2014.11.0... . Previousstudies that tested cut-off points developed based on their samples showed high values for both sensitivity and specificity¹⁵15. Moraes MM, Veiga GV. Acurácia da gordura corporal e do perímetro da cintura para predizer alterações metabólicas de risco cardiovascular em adolescentes. Arq Bras Endocrinol Metabol 2014; 58(4): 341-51. http://dx.doi.org/10.1590/0004-2730000002865
http://dx.doi.org/10.1590/0004-273000000... ^,3939. Bergmann GG, Gaya A, Halpern R, Bergmann ML, Rech RR, Constanzi CB, etal. Waist circumference as screening instrument for cardiovascular disease risk factors in schoolchildren. J Pediatr (Rio J) 2010; 86(5): 411-6. http://dx.doi.org/10.2223/JPED.2026
http://dx.doi.org/10.2223/JPED.2026... ^,4242. Quadros TM, Gordia AP, Silva RC, Silva LR. Predictive capacity of anthropometric indicators for dyslipidemia screening in children and adolescents. J Pediatr (Rio J) 2015; 91(5): 455-63. https://doi.org/10.1016/j.jped.2014.11.006
https://doi.org/10.1016/j.jped.2014.11.0... . Thus, we can reasonably affirm that the success of screening for cardiovascular risk factors in children and adolescents using anthropometric indices might be related to the development and use of specific cut-off points for each population.

Themain strength of this study was assessing the ability of different BMI, WC, and WHtR cut-off points in screening high BP in a school-based probabilistic sample consisting of Brazilian children and adolescents of both genders. However, our study has limitations such as measuring BP on a single occasion, which might have overestimated its high prevalence. At least three visits on different days are recommended to diagnose hypertension, since BP values can fluctuate, especially among children and adolescents due to their excitability for activities that are not part of their routine, such as BP measurement. For this reason, the present study focused on abnormal BP values, using the term “high BP” instead of hypertension. Also, taking measurements in two or more different occasions is operationally complicated in population studies³3. Magliano ES, Guedes LG, Coutinho ES, Bloch KV. Prevalence of arterial hypertension among Brazilian adolescents: systematic review and meta-analysis. BMC Public Health 2013; 13: 833. https://doi.org/10.1186/1471-2458-13-833
https://doi.org/10.1186/1471-2458-13-833... . Another limitation was using a cross-sectional design in our study, which did not allow us to establish a causal relationship between anthropometric indices and BP. Regarding the external validity of the study, we underline that, as shown in a previous study³³33. Quadros TM, Gordia AP, Silva LR, Silva DA, Mota J. Inquérito epidemiológico em escolares: determinantes e prevalência de fatores de risco cardiovascular. Cad Saúde Pública 2016; 32(2): e00181514. http://dx.doi.org/10.1590/0102-311X00181514
http://dx.doi.org/10.1590/0102-311X00181... , the present research was conducted with a sample of children and adolescents from the Northeast region of Brazil, with predominance of monthly household income below the minimum wage, maternal schooling inferior to eight years of study, and social classes C, D, and E. The specific socioeconomic and demographic profile of the young people studied does not allow the extrapolation of our findings to populations from other countries or even other regions of Brazil with distinct characteristics to those investigated here.

CONCLUSION

Despite the association between anthropometric indices and the outcome analyzed, the cut-off points found in the literature were unsatisfactory for high BP screening in the sample investigated. Developing an epidemiological survey with national representation to determine specific cut-off points could enable the use of anthropometric indices in high BP screening in Brazilian children and adolescents. Despite the number of cut-off points available in the literature at the moment, public policies that stimulate and enable the use of BMI and WC as part of monitoring the growth and development of the pediatric population in schools and family health units should be encouraged. We emphasize that the routine clinical evaluation of children and adolescents should include measuring their BP, regardless of their current weight.

ACKNOWLEDGMENTS

To the Municipal Secretariats of Education and Health of Amargosa, BA, Brazil, for the support for the study.

References

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