Body mass index of the elderly and young adult derived from height and knee height

Abstract

Body mass index (BMI) is the widely accepted indicator to determine chronic energy deficiency (CED), and to a lesser extent underweight and overweight. BMI formula WT(kg)/ HT(m2) required the measurement of height (standing height). The question was raised about the appropriateness of height measurement in scoliotic people especially the elderly. Armspan was suggested as a surrogate for height. In the elderly the degenerative changes may occur around the shoulder joints and thus armspan measurement is also questionable. Knee height has been advanced as an another surrogate for height. In this study 43 elderly (age 62-89 years) and 129 young adult (age 22-23 years) were examined to determine the relationship between BMI and BMK (BMI deriving from knee height). It seemed that BMI and BMK correlate very well in both elderly and young adult, male and female with correlation coefficient for the regression were : r = 0.93 (elderly male), r = 0.86 (elderly female), r = 0.90 (young adult male) and r = 0.97 (young adult female). Knee height is a useful measurement to BMK in scoliotic, frail or other diseased elderly.