Height may be difficult to measure for an elderly patient who is bedridden. Kwok and Whitelaw used armspan instead of height to approximate a patient's body mass index (BMI). The authors are from the Leicester Royal Infirmary in England.

Patient selection: adult >= 65 years of age



(1) armspan based on hemispan (halfspan) or full span in meters

(2) body weight in kilograms


arm span =

= 2 * (hemispan)


Measurement device: steel tape, measured to nearest 0.1 cm (1 mm)


Measurement of full arm span:

(1) from middle fingertip to middle fingertip

(2) passing in front of the clavicles

(3) both arms outstreched at 90 degrees to torso (arms roughly in line with both shoulders)


Measurement of hemi-span:

(1) chose an arm not affected by arthritis or deformities if possible

(2) from middle fingertip to the center of the sternal notch

(3) selected arm outstretched at 90 degrees to the torso (arm roughly in line with both shoulders)


body mass index based on armspan =

= (body weight in kilograms) / ((arm span in meters)^2)



• The armspan tends to be slightly less than the height.

• The mean difference between actual and approximate BMI was 1.8 kg per square meter).

• The BMI based on armspan would tend to overestimate the real BMI. If trending the effects of nutritional replacement over time this may not be significant.

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