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Biomedical subjects

A Prader

Publications and source records attributed to A Prader.

224 records · Page 13Linked to original sources
PubMedDate not supplied

The dynamics of linear growth in distance, velocity and acceleration.

Growth of body, leg, trunk and arm length from birth to adulthood is studied in the subjects of the First Zürich Longitudinal Growth Study, using a recently developed technique, the 'structural average curve'. In this way truly longitudinal average curves are obtained for velocity, acceleration and distances, and various phases of growth are analysed not only graphically, but also by descriptive parameters in terms of timing, intensity and duration. These phases consist of the pubertal spurt (PS), the mid-growth spurt (MS) and growth in infancy. The overall pattern is the same in all variables studied: velocity drops sharply after birth, followed by a kink between 7 and 12 months, and a more gradual decrease until the MS, which peaks around 7 years. In girls the PS immediately follows the MS, while in boys a 'latency period' of approximately constant growth velocity precedes the PS, which occurs almost 2 years later, and is more intense than in girls. There are no appreciable sex differences in the MS, but the PS is later and more intense for boys, even when accounting for the smaller adult size of girls. When comparing linear variables the PS turns out to be earlier for the legs than for the trunk, whereas the trunk has an earlier MS. The trunk starts high in relative distance and in velocity after birth, whereas the legs have a high velocity throughout childhood. In adolescence the trunk again shows more intense growth. Surprisingly, the growth of the arms in many ways resembles more that of the trunk and not that of the legs.

Adolescent↗
PubMedDate not supplied

The dynamics of growth of width in distance, velocity and acceleration.

In this paper the dynamics and intensity of the growth of bihumeral and biiliac width and of humerus and femur bicondylar diameter are studied and compared, and sex differences are established. The analysis is based on a newly introduced statistical tool, the structural average curve for distance, velocity and acceleration. It accounts for individual developmental tempo and allows pooling data for a sample of subjects. In all four variables studied, a sharp decline in velocity after birth is followed by a more gradual decline in infancy and childhood. A mid-growth spurt (MS) at about age 7 can be found in all variables, of about equal timing and intensity for the two sexes. The pubertal spurt (PS) is earlier for girls, and less intense except for biiliac width. The study shows a characteristic pattern across variables of width regarding the intensity of growth in different periods. The accentuated MS and PS for bihumeral width, contrasting with relatively early and small PS for the bicondylar width of femur, are remarkable.

Adolescent↗
PubMedDate not supplied

The dynamics of growth of weight, circumferences and skinfolds in distance, velocity and acceleration.

Based on structural average curves of distance, velocity and acceleration, an analysis of the longitudinally assessed growth of weight, arm and calf circumferences and skinfolds (biceps, triceps, suprailiac, subscapular) was undertaken. The data come from the first Zürich longitudinal growth study and represent a normal sample. In addition to a graphic analysis, timing, intensity and duration of the mid-growth spurt (MS) and of the pubertal spurt (PS) are quantified via descriptive parameters of growth. Mechanisms are different and more complex for these variables, in particular for skinfolds, compared to previously studied somatic variables, such as height. Skinfolds showed a rapid decline to a negative velocity minimum in the first year, recovering to a pre-PS fat spurt, earlier and more pronounced for central (suprailiac, subscapular) than for peripheral skinfolds (biceps, triceps). At age of peak height velocity a drop occurred, stronger for boys, followed by a post-PS spurt. A further analysis demonstrates that these ups and downs in skinfold velocity are mainly due to subjects with thick skinfolds. Weight and circumferences show a distinct MS, with sex-independent characteristics and a strong, sex-dependent PS. Weight and even more arm circumference are delayed compared to height in puberty.

Adolescent↗
PubMedDate not supplied

Measures of body mass and of obesity from infancy to adulthood and their appropriate transformation.

In this paper we investigate first the choice of an appropriate index of body mass. The traditional indices weight/height (W/H), W/H2 and W/H3 are compared, as well as an approach due to Cole (1986) making the index W/Hp age-dependent, i.e. by allowing the power p to depend on age. While there may be no perfect index reflecting over- and underweight--irrespective of height and width--the Quetelet index W/H2 turned out to be a reasonable index from childhood to adulthood. Second, we study the development of the body mass index W/H2 longitudinally from birth onwards, based on structural average distance, velocity and acceleration curves. As a third topic, transformations for obtaining an approximate normal distribution for W/H2, weight and skinfolds are compared. The usual log-transformation turned out to be unsatisfactory. While for height and arm skinfolds a transformation -1/square root of x performs rather well across age and sex, a transformation -1/x is more appropriate for trunk skinfolds and W/H2.

Age Factors↗
PubMedDate not supplied

Development and outcome of indices of obesity in normal children.

Based on the Zürich longitudinal growth study, differences are analyzed between those children who later became light adults (later light) and those who later became heavy (later heavy) adults. This is of interest to discover how and when overweight develops, and which variables are most affected (weight, body mass index, circumferences and skinfolds are studied). A further question is whether maturation proceeds differently in these children. The principal idea is to split the sample with respect to adult body mass index into three parts, and to analyse the two extreme groups. It is shown that structural average curves for these subgroups lead to a substantial insight into the processes going on in different variables. Whereas maturation is not much different, subjects later heavy gain substantially more in fat and body mass index from about 4 to 5 years onwards. The natural pattern of ups and downs becomes exaggerated in subjects who are to become heavy at adult age. In those phases where it is natural to build up body mass index there is not much of a difference. In phases where later lean subjects hardly increase their body mass index, later heavy subjects continue to build it up substantially.

Adolescent↗
PubMedDate not supplied

A longitudinal study of lean and fat areas at the arm.

Using biceps and triceps skinfolds and upper arm circumference, areas of fat and lean tissue at the arm can be approximately determined based on a cylindrical assumption. Based on the first Zürich growth study a longitudinal analysis of estimated fat and lean areas is undertaken. Area may often be a more meaningful parameter than width in development, due to the increasing width of the limbs stretching the layer of fat. When comparing these quantities with the body mass index, correlations in boys were higher for lean area than for fat area, and about equally high for both measures in girls (around 0.8 beyond age 10). The primary goal of this investigation was to quantify the development of lean and fat arm areas from birth to adulthood, and to assess sex differences in this respect. The comparison with results obtained earlier from radiographic data is of particular interest, since such data can rarely be obtained any more, and overall this comparison can be considered encouraging. Lean area develops slowly until the onset of puberty, girls showing a slightly smaller value than boys. The pubertal spurt is very impressive in boys and moderate in girls, timed to age of peak height velocity in both sexes. Fat area changes only minimally in boys older than 16 months, and increases steadily in girls until age 16. The respective velocity curve shows a systematic up and down until age 5, when a gradual increase to a prepubertal fat spurt starts. It is interrupted by a trough in velocity--much more accentuated in boys--at puberty, and followed by a postpubertal fat spurt. When studying subgroups of subjects with a relatively high or relatively low adult body mass index, the heavy group differed relatively more in terms of fat area than lean area. Girls heavy as adults increase their fat area consistently more from about 5 years onwards. Boys later heavy show a qualitatively different pattern in puberty, with accentuated pre- and postpubertal fat spurts, but also a strong trough to a negative velocity in between.

Adipose Tissue↗
PubMedDate not supplied

Prediction of adult skinfolds and body mass from infancy through adolescence.

In this paper age-to-age correlations for the body mass index and for skinfolds are evaluated for a sample of normal children studied from birth to adulthood. While correlations over larger age spans are modest, they become appreciable from childhood to adolescence and from adolescence to adulthood. Correlations are consistently higher for boys compared to girls, and only for the former does the body mass index correlate better than skinfolds. Significant correlations between weight increase in the first year and the adult body mass index were found, as well as between the age of 'adiposity rebound' and the adult body mass index. However, the small size of the correlations forbids any predictive applications. As it turns out, the individual prediction of the adult size of the body mass index or of skinfolds is a thorny problem, whatever variables and methods are chosen. The precision of such a prediction is very low up to late childhood and becomes somewhat better in adolescence. From a positive side, this leaves much room for overweight children to improve their state. On the other hand, the relative risk for becoming a heavy adult is much increased for those who are already heavy as children and adolescents. This underlines the dangers of early overweight from an epidemiological viewpoint.

Adolescent↗