Free
Correspondence  |   February 2018
Taller People Should Have as Their Normal a Higher Body Mass Index
Author Notes
  • Albert Einstein Medical Center, Philadelphia, Pennsylvania. Rothj@einstein.edu
  • This letter was sent to the author of the original article referenced above, who declined to respond. —Evan D. Kharasch, M.D., Ph.D., Editor-in-Chief.
    This letter was sent to the author of the original article referenced above, who declined to respond. —Evan D. Kharasch, M.D., Ph.D., Editor-in-Chief.×
  • (Accepted for publication November 2, 2017.)
    (Accepted for publication November 2, 2017.)×
Article Information
Correspondence
Correspondence   |   February 2018
Taller People Should Have as Their Normal a Higher Body Mass Index
Anesthesiology 2 2018, Vol.128, 424. doi:10.1097/ALN.0000000000001998
Anesthesiology 2 2018, Vol.128, 424. doi:10.1097/ALN.0000000000001998
To the Editor:
In their letter, Moreault et al. suggest using a constant body mass index (BMI) to compute ideal body weight.1  Although I agree that this would simplify a commonly used calculation, and the magnitude of any error is small and likely not clinically consequential in this context, this letter provides an opportunity to point out a little appreciated concept: namely, that the normal BMI for a taller patient should be larger.
BMI is calculated as weight (a measure proportional to length [L] cubed, via density) divided by height (length) squared. If as one grows in height, much of the body also grows in width and depth, then the mathematics dictate BMI increases as the height increases (i.e., L3/L2 increases as L increases for L greater than one). This relationship is very apparent if one inspects the pediatric charts of BMI versus age with the understanding that height increases with age. In adults, the increase in BMI with height relationship can be demonstrated by calculating the BMI as a function of height from any of the ideal body weight formulas (e.g., Acute Respiratory Distress Syndrome Network, also known as ARDSnet).2  The Corpulence Index (Ponderal Index, Rohrer’s Index) is computed as weight divided by height cubed, and seems to fluctuate less with height than BMI, but in medical journals, it is not commonly used for adults.3 
This concept may be more significant when stratifying patients into obesity-related categories. For those on the border, this may inappropriately place a taller patient into the more obese category than dictated by physiology.
Competing Interests
The author is six feet six inches tall.
Jonathan V. Roth, M.D., Albert Einstein Medical Center, Philadelphia, Pennsylvania. Rothj@einstein.edu
References
Moreault, O, Lacasse, Y, Bussières, JS . Calculating ideal body weight: Keep it simple. Anesthesiology 2017; 127:203–4 [Article] [PubMed]
Acute Respiratory Distress Syndrome Network: Ventilation with lower tidal volumes as compared with traditional tidal volumes for acute lung injury and the acute respiratory distress syndrome. N Engl J Med 2000; 342:1301–8 [Article] [PubMed]
Rohrer, F . The index of body fullness as a measure of nutritional status [article in German]. Münchner Med Wschr 1921; 68: 580–2