Corpulence index

The Corpulence Index (CI) or Ponderal Index (PI) is a measure of leanness (corpulence) of a person^[1] calculated as a relationship between mass and height.^[2] It was first proposed in 1921 as the "Corpulence measure" by Swiss physician Fritz Rohrer^[3] and hence is also known as Rohrer's Index.^[4] It is similar to the body mass index, but the mass is normalized with the third power of body height rather than the second power.^[5]

${\displaystyle \mathrm {CI} ={\frac {\mathrm {mass} }{\mathrm {height} ^{3}}}}$

with ${\displaystyle \mathrm {mass} }$ in kilograms and ${\displaystyle \mathrm {height} }$ in metres, giving a measure with the same dimensions as density. The corpulence index yields valid results even for very short and very tall persons,^[6] which is a problem with BMI — for example, an ideal height-adjusted body weight for a person 150 cm tall will render BMI of 20.7 and CI of 13.6, while for a person 200 cm tall the BMI will be 24.84, very close to the "overweight" threshold of 25, while CI will be 12.4.^[7]

Because of this property, it is most commonly used in pediatrics.^[8][9] (For a baby, one can take crown-heel length for the height.^[10]) The normal values for infants are about twice as high as for adults, which is the result of their relatively short legs.^{[citation needed]} It does not need to be adjusted for age after adolescence.^[5] It has also been shown to have a lower false positive rate in athletes.^[11]

The corpulence index is variously defined (the first definition should be preferred due to the use of SI-units kg and m) as follows:

Formula	Units for mass (body weight)	Units for height (or length)	Values considered normal or typical
			for a 12-month-old infant	beyond infancy
${\displaystyle {\text{CI}}={\frac {\mathrm {mass} }{\mathrm {height} ^{3}}}}$[9]	kilograms	metres	24[8]	12[5]
${\displaystyle {\text{CI}}=1000{\frac {\mathrm {mass} }{\mathrm {height} ^{3}}}}$[8]	grams	centimetres	(same values as above)
${\displaystyle {\text{CI}}={\frac {\mathrm {height} }{\sqrt[{3}]{\mathrm {mass} }}}}$[1][12]	pounds	inches	12.49 to 13.92

Significance[]

• It plays a role in assessing whether the intrauterine growth restriction of a child is symmetrical or asymmetrical.^[13]
• CI has been shown to have higher sensitivity, specificity, as well as both positive and negative predictive values than body mass index.^[5]

See also[]

• Body adiposity index
• Body mass index
• Waist-to-height ratio

References[]

External links[]

• Online Ponderal Index Calculator, which uses the first definition.
• Ponderal Index Calculator, which uses metric values. (German site)
• Android App for Corpulence Index
• Apple app for Corpulence Index