Pubertal growth in height, sitting height and leg length in achondroplasia.

Background: Children with achondroplasia (ACH) appear to lack a pubertal growth spurt in height.Aim To explore the growth spurt in height and its segments sitting height and leg length, in a large sample of ACH cases using growth curve modelling.Subjects and methods: Height and sitting height were measured longitudinally in ACH children, and the data were analysed using the SITAR (SuperImposition by Translation and Rotation) growth model, which estimates a mean growth curve and random effects for individuals defining differences in size, pubertal timing and intensity.Results: Out of 402 ACH children, 85 boys and 75 girls aged 7-20 years had respectively 529 and 454 measurements of height and sitting height, with leg length calculated by difference. SITAR analysis identified peaks in mean height velocity at 13.3 and 11.3 years in boys and girls, with peak velocities of 4.3 and 4.4 cm/year. Mean peak velocity for sitting height was 3.0 cm/year, but leg length showed no peak. The SITAR models explained 92% to 99% of the cross-sectional variance.Conclusion: ACH children do experience a growth spurt in puberty, but only half that of control children. The spurt is due entirely to sitting height, with no leg length spurt.

Extended international (IOTF) body mass index cut-offs for thinness, overweight and obesity.

BACKGROUND: The international (International Obesity Task Force; IOTF) body mass index (BMI) cut-offs are widely used to assess the prevalence of child overweight, obesity and thinness. Based on data from six countries fitted by the LMS method, they link BMI values at 18 years (16, 17, 18.5, 25 and 30 kg m(-2)) to child centiles, which are averaged across the countries. Unlike other BMI references, e.g. the World Health Organization (WHO) standard, these cut-offs cannot be expressed as centiles (e.g. 85th). METHODS: To address this, we averaged the previously unpublished L, M and S curves for the six countries, and used them to derive new cut-offs defined in terms of the centiles at 18 years corresponding to each BMI value. These new cut-offs were compared with the originals, and with the WHO standard and reference, by measuring their prevalence rates based on US and Chinese data. RESULTS: The new cut-offs were virtually identical to the originals, giving prevalence rates differing by < 0.2% on average. The discrepancies were smaller for overweight and obesity than for thinness. The international and WHO prevalences were systematically different before/after age 5. CONCLUSIONS: Defining the international cut-offs in terms of the underlying LMS curves has several benefits. New cut-offs are easy to derive (e.g. BMI 35 for morbid obesity), and they can be expressed as BMI centiles (e.g. boys obesity = 98.9th centile), allowing them to be compared with other BMI references. For WHO, median BMI is relatively low in early life and high at older ages, probably due to its method of construction.

Early and late growth and blood pressure in adolescence.

OBJECTIVE: To assess the effect of growth during infancy and childhood on blood pressure in adolescence. DESIGN: Birth cohort study. SETTING: Pelotas, southern Brazil. PARTICIPANTS: 749 adolescents with complete information on birth weight and gestational age, as well as on anthropometric data at all three follow up visits (mean age 20 months, 42 months, and 15 years). MAIN OUTCOME MEASUREMENTS: Systolic and diastolic blood pressure at adolescence. RESULTS: After controlling for possible confounding variables, birth weight was negatively associated with systolic blood pressure, one unit increase in standard deviation score of birth weight for gestational age was associated with a decrease of 1.23 mm Hg (95% confidence intervals -2.03 to -0.43) in systolic blood pressure. Weight for age z score at the age of 15 years showed a strong positive association with systolic blood pressure, one unit increase in standard deviation score of birth weight for gestational age was associated with an increase of 4.4 mm Hg (95% confidence intervals 3.50 to 5.3). Diastolic blood pressure was not associated with birth weight. For adequate for gestational age infants, the positive association between weight in adolescence and blood pressure became stronger when previous weights were added to the model. CONCLUSION: This study showed that early--as well as--late catch up growth is associated with increased systolic blood pressure in adolescence, whereas only late catch up is related with diastolic blood pressure. These findings suggest that catch up growth, irrespective of age, is associated with increased blood pressure in adolescence.

Neonatal factors predicting childhood height in preterm infants: evidence for a persisting effect of early metabolic bone disease?

OBJECTIVES: Preterm infants are known to remain small during childhood. We previously found that evidence of neonatal metabolic bone disease was associated with reduced length at 18 months. We aimed to further investigate factors predicting childhood height and to test the hypothesis that evidence of early metabolic bone disease is associated with reduced later height. STUDY DESIGN: A cohort of preterm infants was measured prospectively at 18 months (n = 765), 7. 5 to 8 years (n = 772), and 9 to 12 years of age (n = 503). RESULTS: Preterm infants remained short for their age and sex at all follow-ups. Later height was most strongly predicted by parental height and, at 9 to 12 years, by pubertal status. Neonatal factors associated with later height were birth weight SD score, maternal hypertension/toxemia, and a high peak plasma alkaline phosphatase during the neonatal period. After adjustment for these factors plus interim heights, height at 9 to 12 years was greatest in those who were tallest at 7.5 to 8 years, those who had shown the greatest increase in height percentile between 18 months and 7.5 to 8 years and, as expected, those who were pubertal, whereas children with a peak neonatal plasma alkaline phosphatase >1200 IU were significantly shorter. CONCLUSIONS: Childhood height in preterm infants is strongly influenced by genetic factors. However, biochemical evidence of metabolic bone disease during the neonatal period may have a long-term stunting effect persisting up to 12 years later, providing support for current practices that aim to prevent this condition.

Establishing a standard definition for child overweight and obesity worldwide: international survey.

OBJECTIVE: To develop an internationally acceptable definition of child overweight and obesity, specifying the measurement, the reference population, and the age and sex specific cut off points. DESIGN: International survey of six large nationally representative cross sectional growth studies. SETTING: Brazil, Great Britain, Hong Kong, the Netherlands, Singapore, and the United States. SUBJECTS: 97 876 males and 94 851 females from birth to 25 years of age. MAIN OUTCOME MEASURE: Body mass index (weight/height(2)). RESULTS: For each of the surveys, centile curves were drawn that at age 18 years passed through the widely used cut off points of 25 and 30 kg/m(2) for adult overweight and obesity. The resulting curves were averaged to provide age and sex specific cut off points from 2-18 years. CONCLUSIONS: The proposed cut off points, which are less arbitrary and more internationally based than current alternatives, should help to provide internationally comparable prevalence rates of overweight and obesity in children.

PIP: This study aimed to develop an internationally acceptable definition of child overweight and obesity, specifying the measurement, reference population, and age and sex specific cut off points. Data on body mass index (weight/height) were obtained from 6 large nationally representative cross sectional surveys on growth from Brazil, Great Britain, Hong Kong, the Netherlands, Singapore, and the US. The study included 97,876 males and 94,851 females from birth to 25 years of age. For each of the surveys, centile curves were drawn that at age 18 years passed through the widely used cut-off points of 25 and 30 kg/sq. m for adult weight and obesity. The resulting curves were averaged to provide age- and sex-specific cut-off points from 2 to 18 years. The proposed cut off points, which are less arbitrary and more internationally based than current alternatives, should help to provide internationally comparable prevalence rates of overweight and obesity in children.

A method for assessing age-standardized weight-for-height in children seen cross-sectionally.

Weight-for-height standards in children are usually constructed on the basis that the expected weight for a given height does not depend on age, an assumption which is unjustified. The present paper investigates regression standards of age-standardized weight for age-standardized height, the standardization being achieved by expressing weight and height as fractions of the 50th centile for age from a suitable growth standard. The precise choice of standard is not critical. Data on 4631 children from five different countries, exhibiting a wide spectrum of growth status, show that throughout childhood until puberty, the following ratio is appropriate as a simple and convenient index of weight-for-height: age-standardized weight/(age-standardized height)2. During puberty a larger power than 2 is required, so the index as specified is inappropriate. Approximate values for the distribution centiles of the index are suggested. The index may be used to assess degree of malnutrition or obesity, for individuals or groups seen on a single occasion. A slide-rule is described which calculates the index directly, given the child's sex, age, height and weight.

A method of assessing age standardized weight for height in children seen cross sectionally

Weight-for-height standards in children are usually constructed on the basis that the expected weight for a given height does not depend on age, an assumption which is unjustified. The present paper investigates regression standards of age-standardized weight for age-standardized height, the standardization being achieved by expressing weight and height as fractions of the 50th centile for age from a suitable growth standard. The precise choice of standard is not critical. Data on 4631 children from five different countries, exhibiting a wide spectrum of growth status, show that throughout childhood until puberty, the following ratio is appropriate as a simple and convenient index of weight-for-height: age-standardized weight/(age-standardized height). During puberty a larger power than 2 is required, so the index as specified is inappropriate. Approximate values for the distribution centile of the index are suggested. The index may be used to assess degree of malnutrition or obesity, for the individuals or groups seen on a single occasion. A slide-rule is described which calculates the index directly, given the child's sex, age, height and weight. (Summary)