Vinod Anand | 09 Aug 2013

GROWTH AND ITS SPEED AMONGST CHILDREN (Vinod Anand) ENVIRONMENTAL INFLUENCES There is good reason to believe that nutrition is a factor not only in the rate of growth but also in the speed of growth and the ultimate stature achieved. Children known to be on poor diets can be stimulated to grow at a more rapid rate by improvements in their diets. Where the optimum is reached in relation to diet is not so clear. Can children on adequate diets (adequate to the best of our present-day knowledge) be stimulated to grow more by supplements of protein, minerals, vitamins, or anything else? Opinion is divided on this matter. There is also this question, by no means answerable at present: Is more necessarily better? It is also obvious that physical health has an effect on growth. Children with serious organic disease such as congenital heart disease, nephritis, or some of the inborn errors of metabolism do not grow as do normal children. The decreased incidence of serious acute disease in children since the introduction of antibiotics and improved immunization procedures may play a role in the larger size of today’s children. Emotional factors also affect growth. Infants deprived of maternal care fail to gain weight adequately even on excellent diets. But here, as in so many places in human development, the resultant growth depends not only upon the amount and kind of emotional deprivation but also upon the inherent traits of the child reacting to the deprivation. An interesting trend in growth over the last hundred years is thought probably to be related to nutrition. The data on heights and weights of school children indicate that the whole process of growth has been undergoing a speeding-up process. Children born in the 1930s are appreciably larger at age 5 (and probably before) than children born at the beginning of the century. The amount of this secular change is quite considerable. American, British and Swedish data all give similar trends. The average gain between 1880 and 1950 is about one and half cm and half kg per decade at ages 5 to 7 and about two cm and half kg per decade during puberty. The fully grown adult has increased in height about 1 cm per decade for the past century. Hathaway compared the figures obtained by various American investigators from 1902 to 1952. The data from Hathaway’s compilations are averages based on cross-sectional studies. Data from Bayley’s longitudinal study of California children showed a similar increase in size of the children over their parents. The range of heights and weights at all ages has been unaffected over the years. There have been, and still are, big children and adults and little ones But big and little alike are all a little bigger than they used to be. How long has the secular trend been in operation? There is very little Reliable data before 1880; however, Robert, in 1876 made a significant comment in discussing the physical requirements of factory children: A factory child of the present day at the age of 7 years weighs as much as one of 8 did in 1833— each age has gained one year in 40 years”; and Clements comments on the small size of the armor worn in the Middle Ages. In this connection it should be pointed out that uniformly a high socioeconomic level is reflected in greater weight gains. Every study made the world over has shown that those children from the more privileged groups gain more 3 and gain it sooner than the less privileged in any society. . The effect of socioeconomic levels has been demonstrated in many studies (Meredith, 1941). Chinese girls of upper class in Hong Kong grow larger and mature earlier than girls of similar genetic background but of a less favored economic level (Lee, Chang, and Chan, 1963). That economic level makes a difference is a clearly established fact. Why it should be so is not so clear. Probably, like the secular trend, nutrition is a factor, but so too may be other factors, like regularity of sleep and meals, more outdoor exercise, better medical care—factors that go along with a higher level of education and greater ease of life in the more prosperous groups in any society. Does climate have an effect on growth? Mills has made a case for the gradual change in the world temperature to be at least partly responsible for the secular trend. He suggests that difficulty in heat loss may retard human growth as it does in experimental animals. However, current studies on children in the tropics and in temperate and cold regions do not seem to bear out this hypothesis. Race and climate are difficult factors to disentangle from nutrition and socioeconomic level. West African children (Mackay, 1952) are a good deal retarded in relation to American children, but Whites and Negroes in New York City in similar economic circumstances showed no appreciable differences (Michelson, 1944), indicating that race was not a significant factor here. But how about climate? Using age of menarche as a criterion, Ellis gives 14.3 years as the mean age at menarche in Nigerian school girls of upper socioeconomic level and Levine 14.4 years as that of Eskimo girls. Wilson and Sutherland found the expected class difference in school girls in Colombo, Ceylon, to range from 12.8 years for the menarche in the upper group to 14.4 years in the lower, about the same class differential as found in the temperate zone. Japanese children (Ito, 1942) born and reared in California were taller and heavier than children of similar parentage who remained in Japan. The California-reared Japanese children were also more advanced in skeletal development than the children who remained in Japan. This difference is usually attributed to better food and generally better living conditions, although the possible effect of climate cannot be ignored. The effect of climate, if any, on growth is difficult to distinguish from the other variables affecting the children measured; however, it is clear that season has a definite influence on growth. In the Northern Hemisphere, October, November, and December are the months of greatest weight gain, and it may be five or six times as much as during the months of April, May, and June, when weight gain is at a minimum. About two-thirds of the annual gain in weight is made in the fall (the 6 months from September to February) and only one-third in the remaining 6 months of the year. Height gains are maximum in April, May, and June and minimal in September, October, and November. The reason for the seasonal variation is quite unknown. It appears in well-nourished children as well as in poorly nourished ones. Suggestions have been made that hormone secretions are involved or that environmental temperatures or length of day are factors. The age at which the changes of puberty take place is basically a genetically determined phenomenon; nevertheless, malnutrition can delay the events of puberty. In the secular trend the age of puberty is most pronounced. Maturation occurs earlier now than it did a century ago. Kiil found the average age of menarche of Norwegian girls in 1850 to be 17.0 years and in 1950 13.5 years. In the United States the average age of rnenarche has dropped from 14.2 years in 1900 to l2.9yearsin 1950 (Mills, 1950). The effect of the economic depression as measured in Hagerstown, Maryland, was not sufficient to affect the growth of children measured. Nevertheless there was a demonstrable retardation of the age at which both boys and girls matured. Similar data were obtained both in France and in Belgium during World War II. It would appear that the human body has to grow a certain amount before puberty can take place. If growth takes place rapidly, puberty comes early; if growth is slow, puberty must wait until the body has reached the requisite size, or more likely, maturity level. The speed with which the human body can grow is doubtless genetically determined, but the actual speed is the resultant of the genetic potential and the opportunity afforded by the environment. CONCLUSIONS The following conclusions on the nature of human growth seem reasonably substantiated: 1. All children possess the potential for a pattern of growth characteristically human; every child (barring those with gross defects) passes through the same stages as every other child. These stages are related to most of the measurable aspects of growth, such as physical measurements, development of organs, and maturation of function and behavior. 2. The differences among normal children, within the range of the human pattern, are large. These differences are reflected not only in the magnitude of the measurements but in the tempo of growth itself. 3. Correlations exist between various aspects of growth. A child who deviates from the mean with respect to one type of growth is apt to deviate proportionately in other aspects. While correlations between the various aspects of growth are frequent, they are by no means universal; in some children progression is less uniform than in others. 4. Genetic and endocrine factors are responsible for the basic patterns of growth and maturation. These patterns tend to persist through the life span, contributing to the uniformity of individual growth. 5. Genetic patterns can be modified by environmental factors, such as disease, nutrition, emotions. The effect of quantitatively similar environmental factors varies, depending both on the time in the life cycle when specific deprivations occur and, probably, on the genetic makeup of the individual on whom they are acting. PAGE  PAGE 3