QEPS- a new mathematical model describing individual human growth.

• Background: Longitudinal spontaneous human growth from fetal period to adult height often shows systematic nonparallel growth in SD-scores.Systematic modeling of nonparallel growth in SD-scores is lacking. Objective and hypotheses: To develop a new model describing the growth from fetal life to adult height. To model individual growth changes in SDscores, with a limited number of parameters and to quantify the occurrence of nonparallel growth. Method: Longitudinal height is modeled on the cohort from the Swedish growth reference (born 1974, n=3650). The growth values can be described as a sum of four growth functions: Quadratic(Q), Exponential(E), Pubertal(P)and Stopping(S). Key individual parameters of the model expressed in height in cm are translated in corresponding parameters expressed in height SD-scores, addressing different growth periods. The model is tested on 712 girls and 727 boys from a cohort born 1990. Systematic nonparallel growth in SD-scores is classified by non-overlapping 90% confidence intervals in SD-scores. Result: In the prepubertal period 13% (14%) of the girls(boys) had nonparallel growth in SD-scores before 2 years of age and 19% (20%) after 2 years. For the pubertal period we adjusted the SD-scores for the individual timing of puberty and still found 29% (25%) of the girls (boys) having pubertal nonparallel growth. Evaluating over the total growth period 62% (60%) of the girls (boys) had nonparallel growth. Conclusion: The proposed QEPS model can concisely describe a wide variety of growth curves in SD-scores of healthy individuals. More than half of the individuals appear to have systematic nonparallel growth in SD-scores.

Ämnesord

MEDICIN OCH HÄLSOVETENSKAP  -- Klinisk medicin -- Pediatrik (hsv//swe)

MEDICAL AND HEALTH SCIENCES  -- Clinical Medicine -- Pediatrics (hsv//eng)

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