C H A P T E R 5 The aim of this study is to construct a prediction model for abnormal growth in childhood that can be used from birth to the age of four years. Methods Sample Data for this growth study were collected in the South of the Netherlands, in Maas-‐ tricht and near surroundings. Infants were measured from 1995 until 1999 in a longitudinal growth stud14. The study population consisted of 1234 full-‐term non-‐ hospitalized infants, whose parents were both of Caucasian origin and whose health and living circumstances such that neither in the past nor during the study, growth retardation should be expected. Infants were measured, during their regular visits at the Maastricht infant health-‐care centers. The parents were informed about the purpose of the study and their permission and cooperation were requested. The medical ethics committee approved the study. To acquire reliable longitudinal growth curves only those children were included with at least 9 measurements: 6 during the first year of life and three measure-‐ ments with at least 1 measurement a year during the following 3 years. Based on these criteria 372 (30.1%) children out of 1234 could be included in this study. Measurements Length was measured with the Harpenden infantometer in supine position. From the age of 2 years, standing height was measured with a portable stadiometer. Measurements were taken according to the international accepted methods de-‐ scribed before14. Weight was measured using an electronic scale accurate to 1 gram. All measurements were taken by one trained person (A.J.G.M.G.). Based on weight and height the Ponderal Index (PI) and BMI, besides the meas-‐ urements of weight and height, were used to construct a prediction model For each of the 372 children, weight in relation to height is expressed as the PI for infants up to 1 year of age and the BMI thereafter. The Ponderal Index is an ade-‐ quate measure for individuals with a deviating stature; therefore it is more appro-‐ priate for very young children15. The PI is defined as: PI = 100 × weightgr 78 ! 16 heightcm The BMI is defined as:
Proefschrift binnenwerk Manon Ernst_DEF.indd
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