Clinical Nutrition ESPEN 11 (2016) e70
Contents lists available at ScienceDirect
Clinical Nutrition ESPEN journal homepage: http://www.clinicalnutritionespen.com
Letter to the Editor
The new body mass index as a predictor of postoperative complications in elective colorectal cancer surgery
Keywords: BMI Body mass index Colorectal cancer surgery
of p obtained with different adult population samples are generally 1.1e2.5 and, as noted by Quetelet, would be 3 for hypothetical individuals of identical shape [3]. It is commonly stated that it was Quetelet who formulated the BMI [1,2], but, although he did note that adult weight tends to vary with the square of height, he proposed no such index. Improving on the BMI in particular clinical contexts by the use of different p values is not to be dismissed, but a more hopeful approach is likely to be the replacement of ‘height’ in the BMI or Benn Index with ‘sitting height’ [4]. Conflicts of interest
Dear Editor, A recent article [1] compared two versions of the body mass index (BMI) as predictors of postoperative complications in elective colorectal cancer surgery. The established BMI is calculated as (body weight, kg)/(height, m)2. As for the ‘new Body Mass Index’, the two statements of its formula contain misprints, but the blog [2] in which it was tentatively proposed show it to be 1.3 (body weight, kg)/(height, m)2.5. Thus the new version equals the conventional one multiplied by (1.69/height)0.5, which is 1.00 for a height of 1.69 m. This means that the two versions will be numerically similar for heights close to 1.69 m (between the means of 1.65 m for females and 1.77 m for males). The correlation between the two is not stated, but unpublished trials with various other data sets to hand indicate that the correlation coefficients would have exceeded 0.99. It is therefore unsurprising that the study demonstrated no significant difference between the two versions of BMI in regard to the prediction of postoperative complications in the 1614 patients. Indeed neither version revealed any significant influence of BMI on postoperative outcomes. What did correlate significantly with postoperative complications were higher age, male sex, higher ASA classification and the use of conventional (open), as opposed to laparoscopic, surgery. Use of the BMI has often been challenged [1,2], so that attempts to improve on it are welcome. Both versions of the BMI are special cases of the Benn Index, weight/heightp, in which the height exponent p is taken as 2, this being the round number that generally minimizes the correlation between the index and height [3]. Values
None. Financial support None.
References [1] van Vugt JLA, Cakir H, Kornmann VNN, Doodeman HJ, Stoot JHMB, Boerma D, et al. The new Body Mass Index as a predictor of postoperative complications in elective colorectal cancer surgery. Clin Nutr 2015;34:700e4. [2] Wilton P. Does my BMI look big in this?. 16 Jan 2013. Available from: http:// www.ox.ac.uk/news/science-blog/does-my-bmi-look-big. [3] Burton RF. Why is the body mass index calculated as mass/height2, not as mass/ height3? Ann Hum Biol 2007;34:656e63. [4] Burton RF. Sitting height as a better predictor of body mass than total height and (body mass)/(sitting height)3 as an index of build. Ann Hum Biol 2015;42:210e4.
Richard F. Burton* School of Life Sciences, College of Medical, Veterinary and Life Sciences, University of Glasgow, West Medical Building, Glasgow, G12 8QQ, UK *
Tel.: þ44 (0) 141 334 9738; fax: þ44 (0) 141 330 5481. E-mail address: [email protected].
http://dx.doi.org/10.1016/j.clnesp.2015.08.004 2405-4577/© 2015 European Society for Clinical Nutrition and Metabolism. Published by Elsevier Ltd. All rights reserved.
3 August 2015
Contents lists available at ScienceDirect
Clinical Nutrition ESPEN journal homepage: http://www.clinicalnutritionespen.com
Letter to the Editor
The new body mass index as a predictor of postoperative complications in elective colorectal cancer surgery
Keywords: BMI Body mass index Colorectal cancer surgery
of p obtained with different adult population samples are generally 1.1e2.5 and, as noted by Quetelet, would be 3 for hypothetical individuals of identical shape [3]. It is commonly stated that it was Quetelet who formulated the BMI [1,2], but, although he did note that adult weight tends to vary with the square of height, he proposed no such index. Improving on the BMI in particular clinical contexts by the use of different p values is not to be dismissed, but a more hopeful approach is likely to be the replacement of ‘height’ in the BMI or Benn Index with ‘sitting height’ [4]. Conflicts of interest
Dear Editor, A recent article [1] compared two versions of the body mass index (BMI) as predictors of postoperative complications in elective colorectal cancer surgery. The established BMI is calculated as (body weight, kg)/(height, m)2. As for the ‘new Body Mass Index’, the two statements of its formula contain misprints, but the blog [2] in which it was tentatively proposed show it to be 1.3 (body weight, kg)/(height, m)2.5. Thus the new version equals the conventional one multiplied by (1.69/height)0.5, which is 1.00 for a height of 1.69 m. This means that the two versions will be numerically similar for heights close to 1.69 m (between the means of 1.65 m for females and 1.77 m for males). The correlation between the two is not stated, but unpublished trials with various other data sets to hand indicate that the correlation coefficients would have exceeded 0.99. It is therefore unsurprising that the study demonstrated no significant difference between the two versions of BMI in regard to the prediction of postoperative complications in the 1614 patients. Indeed neither version revealed any significant influence of BMI on postoperative outcomes. What did correlate significantly with postoperative complications were higher age, male sex, higher ASA classification and the use of conventional (open), as opposed to laparoscopic, surgery. Use of the BMI has often been challenged [1,2], so that attempts to improve on it are welcome. Both versions of the BMI are special cases of the Benn Index, weight/heightp, in which the height exponent p is taken as 2, this being the round number that generally minimizes the correlation between the index and height [3]. Values
None. Financial support None.
References [1] van Vugt JLA, Cakir H, Kornmann VNN, Doodeman HJ, Stoot JHMB, Boerma D, et al. The new Body Mass Index as a predictor of postoperative complications in elective colorectal cancer surgery. Clin Nutr 2015;34:700e4. [2] Wilton P. Does my BMI look big in this?. 16 Jan 2013. Available from: http:// www.ox.ac.uk/news/science-blog/does-my-bmi-look-big. [3] Burton RF. Why is the body mass index calculated as mass/height2, not as mass/ height3? Ann Hum Biol 2007;34:656e63. [4] Burton RF. Sitting height as a better predictor of body mass than total height and (body mass)/(sitting height)3 as an index of build. Ann Hum Biol 2015;42:210e4.
Richard F. Burton* School of Life Sciences, College of Medical, Veterinary and Life Sciences, University of Glasgow, West Medical Building, Glasgow, G12 8QQ, UK *
Tel.: þ44 (0) 141 334 9738; fax: þ44 (0) 141 330 5481. E-mail address: [email protected].
http://dx.doi.org/10.1016/j.clnesp.2015.08.004 2405-4577/© 2015 European Society for Clinical Nutrition and Metabolism. Published by Elsevier Ltd. All rights reserved.
3 August 2015
