Journal of Human Hypertension (2015) 29, 211–212 © 2015 Macmillan Publishers Limited All rights reserved 0950-9240/15 www.nature.com/jhh
COMMENTARY
Adiposity indicators and blood pressure in children: nothing beyond body mass index? A Chiolero
Journal of Human Hypertension (2015) 29, 211–212; doi:10.1038/ jhh.2014.96; published online 23 October 2014
Obesity is a major risk factor for elevated blood pressure in children.1–4 For instance, in a school-based study of 5207 children aged 10–12 years, the prevalence of hypertension, which is sustained elevated blood pressure over several visits, was 1.5%, 3.9% and 17.5% in normal weight, overweight and obese children, respectively.4 High body mass index (BMI) is commonly used to define overweight and obesity. However, because BMI is merely a proxy for adiposity, there is a longstanding debate about its performance to predict elevated blood pressure (or any other health conditions associated with adiposity) and whether other adiposity indicators, such as waist circumference, waist-to-hip ratio or hip circumference, should not be preferred.5,6 The study by Dong et al.7 in the current issue of the Journal of Human Hypertension offers a high quality and enlightening contribution to this debate.7 Indeed, the authors assessed the association between different adiposity indicators and elevated blood pressure in a huge population-based study of 99 366 participants aged 7–17 years from China. The adiposity indicators evaluated were weight, BMI, waist circumference, waist-to-height ratio, hip circumference, body adiposity index (a construct based on hip circumference and height), waist-to-hip ratio and skinfold thickness, all converted into z-scores. In this study, 7.4% of boys and 6.4% of girls had elevated blood pressure. The adiposity indicators were highly correlated to each other, apart from weight, waist-to-hip ratio and skinfold thickness z-scores. All indicators were associated with blood pressure. The ability to identify children with elevated blood pressure, assessed by the area under the receiver operating curve (AUC) statistic, was superior for BMI, body adiposity index and waist-to-height ratio z-scores compared with other indicators. BMI z-scores had a slightly higher AUC than other indicators. The authors concluded that BMI z-scores could be a better predictor of elevated blood pressure in children than other adiposity indicators. They also
concluded that abdominal adiposity indicators (for example, waist circumference or waist-to-hip ratio) has not added values over BMI to predict elevated blood pressure and called for further studies to verify their findings. On one hand, the findings by Dong et al.7 are consistent with other studies showing that adiposity indicators other than BMI are similar or weaker predictors of elevated blood pressure in children compare with BMI itself.5,6 On the other hand, their findings could seem at odds with other studies having shown a weaker ability of BMI to predict elevated blood pressure compared with other adiposity indicators, and in particular waist circumference which is commonly considered as a valid proxy for abdominal visceral fat.8–10 However, in these later studies, the differences in the discriminative power of BMI and other adiposity indicators were modest, that is, not clinically relevant. Key to understand the coherence between all these observations is the high correlations between most adiposity indicators.11,12 That was elegantly demonstrated in 380 children and adolescents aged 5–18 years, in whom total fat mass was assessed with dual-energy X-ray absorptiometry and all anthropometric measurements were made by trained technicians using standard techniques.12 The correlation structure between adiposity indicators shows the very high correlations between total fat mass, BMI and waist-circumference (Table 1). With such correlations, it is merely impossible for one indicator to perform largely better than others indicators in identify elevated blood pressure or any other health outcomes associated with adiposity.11,12 Interestingly, the abdominal visceral fat was also measured in these 380 children and adolescents using magnetic resonance imaging. The correlation between abdominal visceral fat and waist circumference was found to be lower than the correlation between total fat mass and waist circumference (Table 1). It suggests that, contrary to what is commonly accepted, waist circumference is not a specific proxy for abdominal visceral fat.12 Actually, as it was more highly correlated with total fat mass than with abdominal visceral fat, waist circumference could be considered merely as an indicator of total fat mass, like BMI.
Table 1.
Age-adjusted partial correlation between total fat mass (measured by dual-energy X-ray absorptiometry), abdominal visceral fat (measured by magnetic resonance imaging), body mass index and waist circumference in 380 children and adolescents aged 5–18 years
Total fat mass Abdominal visceral fat Body mass index Waist circumference
Total fat mass
Abdominal visceral fat
Body mass index
Waist circumference
1 0.83 0.96 0.95
1 0.84 0.81
1 0.96
1
Adapted from Katzmarzyk et al.12
Institute of Social and Preventive Medicine (IUMSP), Lausanne University Hospital, Lausanne, Switzerland. Correspondence: Dr A Chiolero, Institute of Social and Preventive Medicine (IUMSP), Lausanne University Hospital (CHUV), Biopôle 2, 1010 Lausanne, Switzerland. E-mail: [email protected]
Commentary
212 One other argument in favor of BMI is the relative ease to obtain accurate estimation in children. It is indeed more difficult to measure waist or hip circumference than weight and height to compute BMI. The reliability of weight and height measurements has been shown to be higher than the reliability of waist circumference and hip circumference measurements.13,14 Further, pediatricians measure weight and height at each visit in growing children but they are not trained to measure (nor to use) waist or hip circumferences in their daily activities. All these arguments confirm that Dong et al. are probably right to prefer BMI over other adiposity indicators to predict elevated blood pressure in children. CONFLICT OF INTEREST The author declares no conflict of interest.
REFERENCES 1 Díaz ME. Hypertension and obesity. J Hum Hypertens 2002; 16(Suppl 1): S18–S22. 2 Chiolero A, Madeleine G, Gabriel A, Burnier M, Paccaud F, Bovet P. Prevalence of elevated blood pressure and association with overweight in children of a rapidly developing country. J Hum Hypertens 2007; 21: 120–127. 3 McCrindle BW. Assessment and management of hypertension in children and adolescents. Nat Rev Cardiol 2010; 7: 155–163. 4 Chiolero A, Cachat F, Burnier M, Paccaud F, Bovet P. Prevalence of hypertension in schoolchildren based on repeated measurements and association with overweight. J Hypertens 2007; 25: 2209–2217.
Journal of Human Hypertension (2015) 211 – 212
5 Reilly JJ, Kelly J, Wilson DC. Accuracy of simple clinical and epidemiological definitions of childhood obesity: systematic review and evidence appraisal. Obes Rev 2010; 11: 645–655. 6 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: 17–20. 7 Dong B, Wang Z, Wang H-J, Ma J. Associations between adiposity indicators and elevated blood pressure among Chinese children and adolescents. J Hum Hypertens 2015; 29: 236–240. 8 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 2000; 24: 1453–1458. 9 Maffeis C, Pietrobelli A, Grezzani A, Provera S, Tatò L. Waist circumference and cardiovascular risk factors in prepubertal children. Obes Res 2001; 9: 179–187. 10 Genovesi S, Antolini L, Giussani M, Pieruzzi F, Galbiati S, Valsecchi MG et al. Usefulness of waist circumference for the identification of childhood hypertension. J Hypertens 2008; 26: 1563–1570. 11 Bouchard C. BMI, fat mass, abdominal adiposity and visceral fat: where is the 'beef'?. Int J Obes 2007; 31: 1552–1553. 12 Katzmarzyk PT, Bouchard C. Where is the beef? Waist circumference is more highly correlated with BMI and total body fat than with abdominal visceral fat in children. Int J Obes 2014; 38: 753–754. 13 Ulijaszek SJ, Kerr DA. Anthropometric measurement error and the assessment of nutritional status. Br J Nutr 1999; 82: 165–177. 14 Chiolero A. Re: "Comparisons of the strength of associations with future type 2 diabetes risk among anthropometric obesity indicators, including waist-to-height ratio: a meta-analysis". Am J Epidemiol 2013; 177: 862.
© 2015 Macmillan Publishers Limited
Copyright of Journal of Human Hypertension is the property of Nature Publishing Group and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use.
COMMENTARY
Adiposity indicators and blood pressure in children: nothing beyond body mass index? A Chiolero
Journal of Human Hypertension (2015) 29, 211–212; doi:10.1038/ jhh.2014.96; published online 23 October 2014
Obesity is a major risk factor for elevated blood pressure in children.1–4 For instance, in a school-based study of 5207 children aged 10–12 years, the prevalence of hypertension, which is sustained elevated blood pressure over several visits, was 1.5%, 3.9% and 17.5% in normal weight, overweight and obese children, respectively.4 High body mass index (BMI) is commonly used to define overweight and obesity. However, because BMI is merely a proxy for adiposity, there is a longstanding debate about its performance to predict elevated blood pressure (or any other health conditions associated with adiposity) and whether other adiposity indicators, such as waist circumference, waist-to-hip ratio or hip circumference, should not be preferred.5,6 The study by Dong et al.7 in the current issue of the Journal of Human Hypertension offers a high quality and enlightening contribution to this debate.7 Indeed, the authors assessed the association between different adiposity indicators and elevated blood pressure in a huge population-based study of 99 366 participants aged 7–17 years from China. The adiposity indicators evaluated were weight, BMI, waist circumference, waist-to-height ratio, hip circumference, body adiposity index (a construct based on hip circumference and height), waist-to-hip ratio and skinfold thickness, all converted into z-scores. In this study, 7.4% of boys and 6.4% of girls had elevated blood pressure. The adiposity indicators were highly correlated to each other, apart from weight, waist-to-hip ratio and skinfold thickness z-scores. All indicators were associated with blood pressure. The ability to identify children with elevated blood pressure, assessed by the area under the receiver operating curve (AUC) statistic, was superior for BMI, body adiposity index and waist-to-height ratio z-scores compared with other indicators. BMI z-scores had a slightly higher AUC than other indicators. The authors concluded that BMI z-scores could be a better predictor of elevated blood pressure in children than other adiposity indicators. They also
concluded that abdominal adiposity indicators (for example, waist circumference or waist-to-hip ratio) has not added values over BMI to predict elevated blood pressure and called for further studies to verify their findings. On one hand, the findings by Dong et al.7 are consistent with other studies showing that adiposity indicators other than BMI are similar or weaker predictors of elevated blood pressure in children compare with BMI itself.5,6 On the other hand, their findings could seem at odds with other studies having shown a weaker ability of BMI to predict elevated blood pressure compared with other adiposity indicators, and in particular waist circumference which is commonly considered as a valid proxy for abdominal visceral fat.8–10 However, in these later studies, the differences in the discriminative power of BMI and other adiposity indicators were modest, that is, not clinically relevant. Key to understand the coherence between all these observations is the high correlations between most adiposity indicators.11,12 That was elegantly demonstrated in 380 children and adolescents aged 5–18 years, in whom total fat mass was assessed with dual-energy X-ray absorptiometry and all anthropometric measurements were made by trained technicians using standard techniques.12 The correlation structure between adiposity indicators shows the very high correlations between total fat mass, BMI and waist-circumference (Table 1). With such correlations, it is merely impossible for one indicator to perform largely better than others indicators in identify elevated blood pressure or any other health outcomes associated with adiposity.11,12 Interestingly, the abdominal visceral fat was also measured in these 380 children and adolescents using magnetic resonance imaging. The correlation between abdominal visceral fat and waist circumference was found to be lower than the correlation between total fat mass and waist circumference (Table 1). It suggests that, contrary to what is commonly accepted, waist circumference is not a specific proxy for abdominal visceral fat.12 Actually, as it was more highly correlated with total fat mass than with abdominal visceral fat, waist circumference could be considered merely as an indicator of total fat mass, like BMI.
Table 1.
Age-adjusted partial correlation between total fat mass (measured by dual-energy X-ray absorptiometry), abdominal visceral fat (measured by magnetic resonance imaging), body mass index and waist circumference in 380 children and adolescents aged 5–18 years
Total fat mass Abdominal visceral fat Body mass index Waist circumference
Total fat mass
Abdominal visceral fat
Body mass index
Waist circumference
1 0.83 0.96 0.95
1 0.84 0.81
1 0.96
1
Adapted from Katzmarzyk et al.12
Institute of Social and Preventive Medicine (IUMSP), Lausanne University Hospital, Lausanne, Switzerland. Correspondence: Dr A Chiolero, Institute of Social and Preventive Medicine (IUMSP), Lausanne University Hospital (CHUV), Biopôle 2, 1010 Lausanne, Switzerland. E-mail: [email protected]
Commentary
212 One other argument in favor of BMI is the relative ease to obtain accurate estimation in children. It is indeed more difficult to measure waist or hip circumference than weight and height to compute BMI. The reliability of weight and height measurements has been shown to be higher than the reliability of waist circumference and hip circumference measurements.13,14 Further, pediatricians measure weight and height at each visit in growing children but they are not trained to measure (nor to use) waist or hip circumferences in their daily activities. All these arguments confirm that Dong et al. are probably right to prefer BMI over other adiposity indicators to predict elevated blood pressure in children. CONFLICT OF INTEREST The author declares no conflict of interest.
REFERENCES 1 Díaz ME. Hypertension and obesity. J Hum Hypertens 2002; 16(Suppl 1): S18–S22. 2 Chiolero A, Madeleine G, Gabriel A, Burnier M, Paccaud F, Bovet P. Prevalence of elevated blood pressure and association with overweight in children of a rapidly developing country. J Hum Hypertens 2007; 21: 120–127. 3 McCrindle BW. Assessment and management of hypertension in children and adolescents. Nat Rev Cardiol 2010; 7: 155–163. 4 Chiolero A, Cachat F, Burnier M, Paccaud F, Bovet P. Prevalence of hypertension in schoolchildren based on repeated measurements and association with overweight. J Hypertens 2007; 25: 2209–2217.
Journal of Human Hypertension (2015) 211 – 212
5 Reilly JJ, Kelly J, Wilson DC. Accuracy of simple clinical and epidemiological definitions of childhood obesity: systematic review and evidence appraisal. Obes Rev 2010; 11: 645–655. 6 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: 17–20. 7 Dong B, Wang Z, Wang H-J, Ma J. Associations between adiposity indicators and elevated blood pressure among Chinese children and adolescents. J Hum Hypertens 2015; 29: 236–240. 8 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 2000; 24: 1453–1458. 9 Maffeis C, Pietrobelli A, Grezzani A, Provera S, Tatò L. Waist circumference and cardiovascular risk factors in prepubertal children. Obes Res 2001; 9: 179–187. 10 Genovesi S, Antolini L, Giussani M, Pieruzzi F, Galbiati S, Valsecchi MG et al. Usefulness of waist circumference for the identification of childhood hypertension. J Hypertens 2008; 26: 1563–1570. 11 Bouchard C. BMI, fat mass, abdominal adiposity and visceral fat: where is the 'beef'?. Int J Obes 2007; 31: 1552–1553. 12 Katzmarzyk PT, Bouchard C. Where is the beef? Waist circumference is more highly correlated with BMI and total body fat than with abdominal visceral fat in children. Int J Obes 2014; 38: 753–754. 13 Ulijaszek SJ, Kerr DA. Anthropometric measurement error and the assessment of nutritional status. Br J Nutr 1999; 82: 165–177. 14 Chiolero A. Re: "Comparisons of the strength of associations with future type 2 diabetes risk among anthropometric obesity indicators, including waist-to-height ratio: a meta-analysis". Am J Epidemiol 2013; 177: 862.
© 2015 Macmillan Publishers Limited
Copyright of Journal of Human Hypertension is the property of Nature Publishing Group and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use.
