Composition of Change in Phase Angle with Age in Japanese Children

Phase angle (PhA) is a value derived from the resistance (R) in intra- and extracellular fluid and the reactance (Xc) in the cell membrane, measured by bioelectrical impedance analysis (BIA). It has also been referred to as a nutritional index that shows the level of cellular activation, becoming a focus of attention in recent years. However, very little is known about the changes in phase angle with age, particularly the changes that occur during the school-age years. In this study, we investigated whether phase angle has a maximum peak velocity (MPV) similar to that of physique, and if a pubertal peak exists whether it is meaningful as a biological parameter in the same way as height growth. The results showed that the age at MPV of phase angle may be proposed as a critical point in the acquisition of health with stronger physical growth and development during the school-age years. Assuming that MPV of phase angle is a critical point in physical growth and development, its involvement in disease needs to be closely observed with this critical point as a juncture since this is also a time period when the thymus of the immune system shows a pubertal peak. At the same time, beyond the pubertal peak of physique, this may be considered a period during which more adult-like physical enhancement and level of health is maintained.