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L Molinari

Publications and source records attributed to L Molinari.

87 records · Page 5Linked to original sources
PubMedDate not supplied

Velocity and acceleration of height growth using kernel estimation.

A method is introduced for estimating acceleration, velocity and distance of longitudinal growth curves and it is illustrated by analysing human height growth. This approach, called kernel estimation, belongs to the class of smoothing methods and does not assume an a priori fixed functional model, and not even that one and the same model is applicable for all children. The examples presented show that acceleration curves might allow a better quantification of the mid-growth spurt (MS) and a more differentiated analysis of the pubertal spurt (PS). Accelerations are prone to follow random variations present in the data, and parameters defined in terms of acceleration are, therefore, validated by a comparison with parameters defined in terms of velocity. Our non-parametric-curve-fitting approach is also compared with parametric fitting via a model suggested by Preece and Baines (1978).

Body Height↗
PubMedDate not supplied

An analysis of the mid-growth and adolescent spurts of height based on acceleration.

Height growth between four weeks and 20 years of 45 boys and 45 girls from the Zürich Longitudinal Growth Study (1955-1976) was analysed using kernel estimates. Timings of the mid-growth spurt (MS) and of the pubertal spurt (PS) were determined in an automatic way from the individual acceleration curves, together with height, percentage of height, velocity and acceleration at these ages. The small mid-growth spurt is a consistent phenomenon, peaking at 6.4 years (M,F) in acceleration and at 7.7 years (M) and 7.5 years (F) in velocity. There are no significant sex differences in its intensity. In girls, the PS follows in close succession to the MS; in boys there is a substantial period in between. In addition to the age of peak height velocity, ages of onset, maximal acceleration and end of the PS are defined. Sex differences in timing and size of the pubertal peak previously established were again verified. New results relate to the asymmetry of the PS, which is more pronounced in girls, and to sex differences in intensity and duration of the first rising phase of the PS. After this phase, boys and girls do not differ in timing but only in the intensity of deceleration.

Adolescent↗
PubMedDate not supplied

Human height growth: correlational and multivariate structure of velocity and acceleration.

In this paper the correlations between parameters quantifying the mid-growth spurt (MS) and the pubertal spurt (PS) of height are explored. These parameters are defined in individual acceleration, velocity, and distance curves, which are obtained via kernel estimates as previously introduced. The MS proves to be a phenomenon largely independent of the PS. Intensity, timing, and duration of the PS are also independent mechanisms of growth and neither of them influences adult height in an appreciable way. Adult height depends mostly on pre-adolescent velocity. Short-, medium- and long-term regulatory mechanisms for explaining height growth are considered. For short-term mechanisms, acceleration plays a crucial role.

Adolescent↗
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↗
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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↗
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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↗
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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↗
PubMedDate not supplied

An analysis of variance of the pubertal and midgrowth spurts for length and width.

Using data from the first Zurich Longitudinal Growth Study characteristics of the growth of six variables--bihumeral width, biiliac width, standing height, sitting height, leg height and arm length--are studied. The main interest is in differences between boys and girls, and across variables and in particular in whether there are sex differences that are specific for some variables. For each child and variable, individual velocity and acceleration curves are estimated using a kernal smoother. From these curves, parameters characterizing the midgrowth spurt (MS) and the pubertal spurt (PS) are estimated: timings, durations and intensities. The level of childhood velocity is used for characterizing early growth. These parameters are analysed using a repeated measures analysis of variance (ANOVA) to assess the statistical significance of differences between boys and girls and across variables. This necessitates some kind of standardization and two types of standardization are used here. The MS shows negligible or small differences between boys and girls, and the same is true for velocity in childhood. Differences across variables during the MS are much more pronounced: with respect to intensity, bihumeral width has an MS about six times more intense than height. The PS is later for boys (as is well known), and there are significant differences across variables: bihumeral width and sitting height are late while legs are early. With the exception of biiliac width, the duration of the PS (which has been subdivided into three phases-early, middle and late) is slightly longer for boys for all variables: boys have a longer starting phase, the middle phase is about equal in length for both boys and girls, and girls have a slightly longer late phase. Leg height and height experience a PS of short duration while bihumeral and biiliac width experience a long one and these differences are highly statistically significant. For all variables, with the exception of biiliac width, boys have a more intense PS (in terms of maximal acceleration), even having adjusted for their larger adult size. Differences in intensity are also marked across variables, bihumeral width and sitting height having the highest intensity and legs the lowest. Differences between sexes and across variables are much smaller for the stopping intensity, characterized by maximal deceleration.

Adolescent↗
PubMedDate not supplied

MR imaging of brain maturation in normal and developmentally handicapped children.

White matter myelination was assessed in the frontal, temporal, and occipital lobes and in the internal capsule in 91 neurodevelopmentally handicapped infants on T2-weighted images (spin echo 3,000/120 ms) and compared with myelination scores from 53 normal control subjects. Clinical diagnosis was birth asphyxia (34), seizures with delays of various causes (33), congenital infections (15), and intracerebral hemorrhages (9). Myelination in the total group of patients was generally delayed. However, we found distinct differences in myelin deposition between groups. Myelination of handicapped children with seizures or with intrauterine infections was retarded most severely at all ages. Children with intracerebral hemorrhages were almost never significantly different from normals in any part of the brain, whereas children with birth asphyxia had myelination scores in between. We conclude that magnetic resonance staging of developmental processes, such as myelination, in the infants' brain helps to recognize delays at an early age.

Asphyxia Neonatorum↗