Analysis of Linear Growth Using a Mathematical Model

Abstract

According to the "ICP-growth model" (ICP = Infancy, Childhood and Puberty components), linear growth during the first three years of life can be represented mathematically by a combination of a sharply decelerating Infancy component and a slowly decelerating Childhood component. Growth as measured by supine length is analysed for 191 longitudinally followed healthy infants using this model. The main aim is to devise ICP-based methods for biological and clinical applications. The onset of the Childhood component, which occurs some time between 6 and 12 months of age and is typically abrupt, can be detected on an individual basis. Its starting point probably defines the as yet unknown age at which growth hormone begins to exert a significant influence. The analyses have also revealed some new facets of linear growth. Most infants are found to have a non-linear decelerating Infancy component, free from seasonal influence. Age at onset of the Childhood component is earlier for girls than for boys and is positively related to the magnitude of the Infancy component. During the second year of life the variation in growth rate of the cohort increases. This fluctuation is found to be seasonal and greater for those with late onset of the Childhood component. During the third year of life the growth pattern is stabilized.

Seasonality of growth in Shanghai infants (n=4128) born in 11 consecutive years

“…It is worth noting that the seasonal in¯uence on linear growth seems to appear as early as in the ®rst few months of life. This contrasted with Swedish studies that reported seasonal variation in length gain during the second year of life, but not during the ®rst 6 months (Karlberg et al, 1987).…”

Individual growth curve models for assessing evidence‐based referral criteria in growth monitoring

“…The starting point of the childhood component represents the age of onset. Most healthy infants show an abrupt increase in growth rate [3]. Finding the exact age at onset of the childhood phase can only be determined when the interval between measurements is small.…”

“…In this paper, we used the JB model, but we also considered the ÿrst two components of the infancy-childhood-puberty (ICP) growth curve model. The ICP growth curve decomposes linear growth mathematically into three additive and partly superimposed components-infancy, childhood and puberty [3]. The starting point of the childhood component represents the age of onset.…”

“…Some parameters correspond to interpretable quantities such as growth at birth, growth velocity, growth acceleration or deceleration. A number of growth curve models have been suggested in the literature and have been shown to be representative at di erent periods of life [2,3]. We considered several of such models, and used the well-known Jenss-Bayley (JB) growth curve for our data.…”

Growth Disorders

“…Karlberg et al have proposed a mathematical model of the phases of human growth -the infancy -childhoodpuberty or ICP model [7,8]. The infancy component begins from midgestation lasting till 2-3 postnatal years.…”