SEASONAL VARIATION OF AVERAGE GROWTH IN WEIGHT OF ELEMENTARY SCHOOL CHILDREN

The rates of av. growth in wt. are highest in the fall months, intermediate in winter, and lowest in spring. The average during the summer is about equal to the rates during February and March. The same cyclic changes occur in both sexes and for each age group from the 6th through the 14th yr. These findings agree, with few exceptions, with the previous work on the subject. During the 6th and 7th yrs., there is no consistent sex difference in the growth rate. During the 8th and 9th yrs., boys apparently grow slightly faster. In the spring of the 10th yr., the rates for girls become greater and remain so until the fall of the 14th yr., when the rates for boys become greater and remain so through the 15th yr. Analysis of the changes with age of growth rates for individual months shows: (a) Maximum growth rates for girls in the 11th and 12th yrs.; (b) for boys in the 14th and 15th yrs. (c) No evidence of a "pre-adolescent slump" or "lag" of av. growth in wt. Suggestive evidence is brought out of a seasonal sex difference in the appearance of the "adolescent acceleration" which in girls is apparently more pronounced in the spring and summer, and in boys in the fall and early winter. Comparison of the monthly growth rates of a selected group of children who were not absent from school during an entire year with the remainder of the group who were absent one or more days because of sickness shows that the typical seasonal variation in growth is not the result of including in the data records of seriously ill children who fail to gain or who lose weight. Comparison of the seasonal curve of monthly growth rates with the seasonal curve of incidence of sickness indicates that there is no concomitant variation between the two.