Twice-daily measurements of stature and body weight in two children and one adult.

Stature and body weight of two children, 12.5 and 9.3 years, and their mother were measured twice daily for 488 days, immediately after rising and just before bed. The time of the measurements was also recorded and diurnal changes during daytime and nighttime were estimated. Stature began to decrease instantaneously after rising. Therefore, morning measurements were made immediately after rising. Stature decreased during the day, and the mean daytime loss was 1.78 cm in the older child, 1.61 cm in the younger child, and 1.43 cm in the adult. Stature increased during sleep hours at night, and the mean nighttime gain was 1.79 cm, 1.63 cm, and 1.43 cm in each subject, respectively. Stature also increased after naps and a bath. Body weight decreased during sleep hours at night, and the mean nighttime loss was 0.46 kg, and 0.38 kg, and 0.36 kg in each subject, respectively. Diurnal changes were largest in the older child, while the ratios of changes (ΔST/ST, ΔWT/WT) were largest in the younger child whose growth rate was the greatest. In the children, the nighttime gain of stature was not as highly correlated with hours of sleep as in the adult. Diurnal change varies depending upon sleep hours and stage of growth. Rapid growth in stature of 1 cm in only three weeks was observed once in the younger child. During this period, diurnal change was smaller than the mean value over 488 days. In the older child, the growth rate decreased in both stature and weight about three months after menarche. © 1993 Wiley-Liss, Inc.