The indentification and evaluation of measurement variability in the anthropometry of preschool children

Early-Life Nutrition and Subsequent International Migration: A Prospective Study in Rural Guatemala

BACKGROUND

It is generally accepted that migrants are favorably self-selected for labor market skills such as higher schooling and greater cognitive capacity, which are highly correlated with early-life nutrition. However, the influence of early-life nutrition on later-life migration is understudied.

OBJECTIVE

The objective of this study was to examine prospectively the association between height-for-age z scores (HAZ) at 24 mo and subsequent international migration in a cohort of 2392 participants born between 1962 and 1977 in 4 rural villages in eastern Guatemala.

METHODS

Information on nutritional status and covariates was collected between 1969 and 1977 and migration status was determined as of 2017 (at ages 40-57 y). We used proportional hazards and logistic regression models to assess whether HAZ was associated with international migration, adjusting for early-life and adult characteristics.

RESULTS

Between 1978 and 2017 there were 297 international migrants (12.4% of the original cohort) during 99,212 person-y of follow-up. In pooled models that were adjusted for early-life characteristics, a 1-SD increase in HAZ was associated with a 19% increase in the risk of international migration (HR: 1.19; 95% CI: 1.02, 1.38). Further adjustment for village characteristics did not alter the estimate substantively (HR: 1.18; 95% CI: 1.02, 1.37), while additional adjustment for schooling attainment attenuated the estimate somewhat (HR: 1.14; 95% CI: 0.98, 1.33). In all models, effect sizes were stronger for men than for women.

CONCLUSIONS

Our results indicate that early-life nutrition is positively associated with subsequent international migration.

Precision of Measurements Performed by a Cadre of Anthropometrists Trained for a Large Household Nutrition Survey in Ethiopia

BACKGROUND

Well-trained anthropometrists are essential for the delivery of high-quality anthropometric data used to evaluate public health nutrition interventions. Scant data are currently available on the precision of data collected by large teams of anthropometrists employed for nutrition surveys in low-income country settings.

OBJECTIVES

The purpose of this study was to assess the precision of child midupper arm circumference (MUAC) and length/height measurements taken by fieldworkers training for nutrition survey deployment.

METHODS

Following 3 d of training, an anthropometry standardization exercise was conducted in small teams of trainees at 7 sites in the Amhara region of Ethiopia. In groups of 2-4, trainee anthropometrists (n = 79) each measured 16 children aged 6-47 mo (n = 336) twice for MUAC and length/height. Both intraobserver and interobserver precision were analyzed using technical error of measurement (TEM), relative TEM, coefficient of reliability (R), and repeatability metrics. Bland-Altman limits of agreement were calculated for intraobserver measurements.

RESULTS

Intraobserver TEM was between 0.00 and 0.57 cm for MUAC (Bland-Altman 95% limits of agreement: -0.50 to 0.54 cm) and between 0.04 and 2.58 cm for length/height measurements (Bland-Altman 95% limits of agreement: -1.43 to 1.41 cm). Interobserver TEM was between 0.09 and 0.43 cm for MUAC and between 0.06 and 2.98 cm for length/height measurements. A high proportion of trainees achieved intraobserver R >0.95 (MUAC: 95%; length/height: 97%). Most teams also achieved interobserver R >0.95 (MUAC: 90%; length/height: 95%).

CONCLUSIONS

Large numbers of anthropometrists (>75) in low-income settings can attain satisfactory precision in anthropometry following training and standardization. These protocols permit researchers to assess trainees, identify individuals who have not achieved the desired level of precision, and retrain or adjust roles prior to survey deployment.

Program Impact Pathways and Contexts: A Commentary on Theoretical Issues and Research Applications to Support the EsIAN Component of Mexico's Conditional Cash Transfer Program

This commentary on the Integrated Strategy for Attention to Nutrition (EsIAN) journal supplement begins with a discussion about the challenges that implementation researchers confront with respect to analyzing complex impact pathways. We note that the research on the implementation of the EsIAN component of Mexico's conditional cash transfer program was based implicitly or explicitly on a program impact pathway approach, which used both quantitative and qualitative methods to examine bottlenecks in program implementation. We then identify 5 categories of contexts that affect the impact, implementation, and survival of intervention programs: 1) biological, 2) social-cultural, 3) delivery modalities and platforms, 4) bureaucratic, and 5) political. Each of these contexts presents theoretical and methodological challenges for investigators. In this commentary, we focus primarily on biological and social-cultural contexts, discussing the theoretical and methodological challenges the investigators faced and the research strategies they used to address them, which have produced a unique compilation of "learning by doing" studies. We also touch briefly on the political context in which the Prospera program research was conducted. We conclude with statements that highlight the exceptional value of the journal supplement, not only with respect to the analysis of the interventions the studies cover and the sustained examination of a long-term program but also as a major contribution to the literature in implementation science in nutrition.

Objectives, Research Design, and Implementation of the Incap Longitudinal Study

The INCAP longitudinal study (1969–1977) was carried out in four Guatemalan villages to assess the effects of intra-uterine and preschool malnutrition on growth and mental development. To achieve this, food supplements were provided to pregnant women and young children. Two villages were given a high-protein, high-energy drink and two a no-protein, low-energy drink. Both supplements contained vitamins and minerals. The key features of the final study design implemented in 1969 are noted, together with its strengths and weaknesses. The selection of the study villages is described in detail, and the nature of the randomized nutritional intervention and that of the medical care programme offered to all the villages are presented. The methods of data collection and quality-control procedures are also detailed. The information should be of interest to those wishing to use and understand the INCAP/Cornell data set.

Home-based anthropometric, blood pressure and pulse measurements in young children by trained data collectors in the National Children's Study

OBJECTIVE

The current study assessed whether home-based data collection by trained data collectors can produce high-quality physical measurement data in young children.

DESIGN

The study assessed the quality of intra-examiner measurements of blood pressure, pulse rate and anthropometric dimensions using intra-examiner reliability and intra-examiner technical error of measurement (TEM).

SETTING

Non-clinical, primarily private homes of National Children's Study participants in twenty-two study locations across the USA.

SUBJECTS

Children in four age groups: 5-7 months (n 91), 11-16 months (n 393), 23-28 months (n 1410) and 35-40 months (n 800).

RESULTS

Absolute TEM ranged in value from 0·09 to 16·21, varying widely by age group and measure, as expected. Relative TEM spanned from 0·27 to 13·71 across age groups and physical measures. Reliabilities for anthropometric measurements by age group and measure ranged from 0·46 to >0·99 with most exceeding 0·90, suggesting that the large majority of anthropometric measures can be collected in a home-based setting on young children by trained data collectors. Reliabilities for blood pressure and pulse rate measurements by age group ranged from 0·21 to 0·74, implying these are less reliably measured with young children when taken in the data collection context described here.

CONCLUSIONS

Reliability estimates >0·95 for weight, length, height, and thigh, waist and head circumference, and >0·90 for triceps and subscapular skinfolds, indicate that these measures can be collected in the field by trained data collectors without compromising data quality. These estimates can be used for interim evaluations of data collector training and measurement protocols.

Measurement and Standardization Protocols for Anthropometry Used in the Construction of a New International Growth Reference

The objective of the Motor Development Study was to describe the acquisition of selected gross motor milestones among affluent children growing up in different cultural settings. This study was conducted in Ghana, India, Norway, Oman, and the United States as part of the longitudinal component of the World Health Organization (WHO) Multicentre Growth Reference Study (MGRS). Infants were followed from the age of four months until they could walk independently. Six milestones that are fundamental to acquiring self-sufficient erect locomotion and are simple to evaluate were assessed: sitting without support, hands-and-knees crawling, standing with assistance, walking with assistance, standing alone, and walking alone. The information was collected by both the children's caregivers and trained MGRS fieldworkers. The caregivers assessed and recorded the dates when the milestones were achieved for the first time according to established criteria. Using standardized procedures, the fieldworkers independently assessed the motor performance of the children and checked parental recording at home visits. To ensure standardized data collection, the sites conducted regular standardization sessions. Data collection and data quality control took place simultaneously. Data verification and cleaning were performed until all queries had been satisfactorily resolved.

Adult consequences of growth failure in early childhood

BACKGROUND

Growth failure is associated with adverse consequences, but studies need to control adequately for confounding.

OBJECTIVE

We related height-for-age z scores (HAZs) and stunting at age 24 mo to adult human capital, marriage, fertility, health, and economic outcomes.

DESIGN

In 2002-2004, we collected data from 1338 Guatemalan adults (aged 25-42 y) who were studied as children in 1969-1977. We used instrumental variable regression to correct for estimation bias and adjusted for potentially confounding factors.

RESULTS

A 1-SD increase in HAZ was associated with more schooling (0.78 grades) and higher test scores for reading and nonverbal cognitive skills (0.28 and 0.25 SDs, respectively), characteristics of marriage partners (1.39 y older, 1.02 grade more schooling, and 1.01 cm taller) and, for women, a higher age at first birth (0.77 y) and fewer number of pregnancies and children (0.63 and 0.43, respectively). A 1-SD increase in HAZ was associated with increased household per capita expenditure (21%) and a lower probability of living in poverty (10 percentage points). Conversely, being stunted at 2 y was associated with less schooling, a lower test performance, a lower household per capita expenditure, and an increased probability of living in poverty. For women, stunting was associated with a lower age at first birth and higher number of pregnancies and children. There was little relation between either HAZ or stunting and adult health.

CONCLUSION

Growth failure in early life has profound adverse consequences over the life course on human, social, and economic capital.

Early childhood diarrhea and cardiometabolic risk factors in adulthood: the Institute of Nutrition of Central America and Panama Nutritional Supplementation Longitudinal Study

BACKGROUND

Nutritional deficits in early life have been associated with a higher prevalence of the metabolic syndrome (MetS) in adulthood. Early childhood diarrhea contributes to undernutrition and may potentially increase the risk for adult noncommunicable diseases. Our objective was to examine associations between early childhood diarrhea burden and later development of MetS.

METHODS

We studied individuals who participated in the Institute of Nutrition of Central America and Panama Nutritional Supplementation Longitudinal Study (1969-1977) and were followed up in 2002-2004. We used logistic regression to determine associations of diarrhea burden at ages 0 to 6, 6 to 12, and 12 to 24 months with odds of MetS and elevations in its components as adults.

RESULTS

Among 389 adults age 25 to 42 years at follow-up, the prevalence of MetS was 29%. Adjusting for several confounders including adult body mass index (BMI), each absolute 1% increase in diarrhea burden at age 0 to 6 months (but not at other time periods) was associated with increased odds of MetS (odds ratio [OR], 1.03; 95% confidence interval [CI], 1.01-1.06). This was attributable primarily to associations with elevated blood pressure (OR, 1.03; 95% CI, 1.00-1.06) and waist circumference (OR, 1.03; 95% CI, 1.00-1.06).

CONCLUSIONS

Childhood diarrhea burden at 0 to 6 months is associated with MetS in adulthood after controlling for childhood growth parameters and adult BMI.

Growth references for 0-19 year-old Norwegian children for length/height, weight, body mass index and head circumference

BACKGROUND

Previous growth references for Norwegian children were based on measurements from the 1970s and 1980s. New reference data, collected through the Bergen Growth Study and the Medical Birth Registry of Norway, are presented as LMS values.

MATERIALS AND METHODS

A cross-sectional sample of children aged 0-19 years in stratified randomized design measured in 2003-2006 as a part of the Bergen Growth Study (n = 7291) and birth data of children born in 1999-2003 from the Medical Birth Registry of Norway (n = 12 576) was used to estimate the new references by the means of the LMS method. Measurement reliability was assessed by test-rest studies.

RESULTS

New references were constructed for length/height, weight, body mass index (BMI) and head circumference. Length/height and weight for children aged 0-4 years were similar to previous Norwegian references, but mean height increased up to a maximum of 3.4 cm in boys and 2.5 cm in girls during the pubertal years. Mean height was similar to (or slightly higher) in comparison with other recent European references. Reliability of the measurements compared well with published estimates.

CONCLUSION

Because of the observed secular trends in growth, it is advised to use the new references, which have been endorsed by the Norwegian Department of Health.

Physical growth and development of the malnourished child: contributions from 50 years of research at INCAP

This paper reviews the main findings and policy implications of 50 years (1949-1999) of research conducted by INCAP on growth and development. Topical areas reviewed include a) maternal size and birthweight and the causes of intrauterine growth retardation (IUGR), b) patterns and causes of postnatal growth retardation, c) the relative importance of genetics and the environment in explaining differences in growth among populations, d) the implications of being small, for both children and adults, e) bone growth and maturation and dental development, f) menarche, and g) methodological contributions such as anthropometric reference data, quality control of data collection, development of risk indicators and use of anthropometry in nutrition surveillance systems. Key contributions to knowledge by INCAP include a) characterization of growth failure and maturational delays as mainly occurring during the intrauterine period and the first 3 years of life b) clarification of the role of small maternal size and of inadequate dietary intakes during pregnancy as major causes of intrauterine growth failure, c) evidence that diarrheal diseases and poor dietary intakes are the principal causes of growth failure in early childhood, d) demonstration that environmental factors related to poverty, and not genetic or racial ancestry, account for most of the differences in growth between populations, e) evidence that growth failure predicts functional impairment in the child as well as in the adult andf) demonstration that nutrition interventions are effective in preventing growth failure and its consequences, if targeted to needy women and young children. INCAP's work has contributed knowledge that has informed and improved policies and programs aimed at overcoming maternal and child undernutrition and promoting optimal growth and development.

Is overweight a risk factor for wheezing in pre-school children? A study in 14 Brazilian communities

OBJECTIVE

To evaluate the association between overweight and wheezing in pre-school children in 14 small Brazilian communities.

METHODS

Cross-sectional epidemiological study, conducted between 2001 and 2002. A sample of 3453 children under 5 years of age was taken from nine communities in the state of Bahia and five in the state of São Paulo. Data on housing, family and children were obtained by applying structured questionnaires in loco. Weight and height for each child were also measured. The association between wheezing and overweight was assessed by unconditional logistic multivariate regression models.

RESULTS

Overweight children had a greater frequency of wheezing and an odds ratio of 2.57 (95% confidence interval 1.51-4.37) was estimated after controlling for several potential confounding variables. The magnitude of the risk was not affected by several different model specifications.

CONCLUSION

Excess weight is associated with increased risk for wheezing in this population of children below 5 years of age.

Reliability of anthropometric measurements in the WHO Multicentre Growth Reference Study

AIM

To describe how reliability assessment data in the WHO Multicentre Growth Reference Study (MGRS) were collected and analysed, and to present the results thereof.

METHODS

There were two sources of anthropometric data (length, head and arm circumferences, triceps and subscapular skinfolds, and height) for these analyses. Data for constructing the WHO Child Growth Standards, collected in duplicate by observer pairs, were used to calculate inter-observer technical error of measurement (TEM) and the coefficient of reliability. The second source was the anthropometry standardization sessions conducted throughout the data collection period with the aim of identifying and correcting measurement problems. An anthropometry expert visited each site annually to participate in standardization sessions and provide remedial training as required. Inter- and intra-observer TEM, and average bias relative to the expert, were calculated for the standardization data.

RESULTS

TEM estimates for teams compared well with the anthropometry expert. Overall, average bias was within acceptable limits of deviation from the expert, with head circumference having both lowest bias and lowest TEM. Teams tended to underestimate length, height and arm circumference, and to overestimate skinfold measurements. This was likely due to difficulties associated with keeping children fully stretched out and still for length/height measurements and in manipulating soft tissues for the other measurements. Intra- and inter-observer TEMs were comparable, and newborns, infants and older children were measured with equal reliability. The coefficient of reliability was above 95% for all measurements except skinfolds whose R coefficient was 75-93%.

CONCLUSION

Reliability of the MGRS teams compared well with the study's anthropometry expert and published reliability statistics.

Relative importance of birth size and postnatal growth for women's educational achievement

BACKGROUND

Child undernutrition, commonly measured by growth failure, is associated with functional disadvantages later in life.

AIMS

To assess relationships between child growth and women's educational achievement (EA).

STUDY DESIGN AND SUBJECTS

Women from four ladino Guatemalan villages were measured as children (1969-1977) and again at ages 20-29 years (1996-1999). The anthropometric measurements analyzed were weight, length, and head circumference (HC) at birth and 2 years and height at adulthood. Sample sizes were 120 at birth, 133 at 2 years, and 145 at adulthood; 108 cases had data at all three points.

OUTCOME MEASURES

Women's EA was computed based on five educational tests and was categorized into quintiles. Analysis was based on a proportional odds model. Generalized estimating equations were used to account for sibling clustering. Multiple Stage Least Squares analyses were used to assess the relative importance of birth size and of early (birth to age 2 years) and late postnatal growth (2 years to adulthood).

RESULTS

Size at 2 years (HC and length) but no indicator at birth was positively associated with women's EA. Schooling was a strong, positive predictor of women's EA (odds ratio (OR)=13.7, 95% confidence interval (CI) [6.1, 30.6]). Early postnatal growth but not birth size or late postnatal growth was associated with women's EA (OR with 1 standard deviation (S.D.) increment in length=1.5, 95% CI [1.05, 2.2]).

CONCLUSIONS

Growth in length and HC from birth to 2 years of age, but not birth size or growth after 2 years, is an important predictor of women's EA.

Associations between prenatal and postnatal growth and adult body size and composition

BACKGROUND

Adult body size and composition (ABSC) measures are associated with work capacity and productivity, reproductive performance, and chronic disease risk. Growth failure in early childhood may have important long-term consequences through its influence on ABSC.

OBJECTIVE

We assessed associations between prenatal and postnatal growth (0-2 y of age) and ABSC.

DESIGN

We included 267 singletons from a prospective study carried out between 1969 and 1977 in 4 ladino Guatemalan villages. We used data from that study and from a follow-up study conducted in 1998-1999 (when the subjects were 21-27 y of age) to determine associations of birth weight, length at 15 d of age, ponderal index, and length at 2 y of age with adult height, weight, fat-free mass (FFM), fat mass, percentage of body fat, and waist-to-hip ratio. Multivariate linear regression analyses with mixed models were carried out to account for sibling clustering. Two-stage least-squares analyses were used to separate specific effects of prenatal and postnatal growth.

RESULTS

Birth weight, length at 15 d of age, and length at 2 y of age were positively associated with height, weight, and FFM in both sexes (P < 0.05). Prenatal growth and postnatal growth were equally important determinants of height, weight, and FFM. Weak positive associations of postnatal growth with adult fat mass and percentage of body fat were found in both sexes, whereas similar associations for prenatal growth were found in women only. Growth in early childhood was not related to waist-to-hip ratio.

CONCLUSIONS

Growth retardation in early childhood was associated with shortness and less FFM in adulthood. Preventing growth failure in utero and preventing growth failure during the first 2 y of life are equally important for ABSC.

Child factor in measurement dependability

A primary consideration in longitudinal growth studies is the identification of growth from error components. While previous research has considered matters of measurement accuracy and reproducibility in detail, few reports have investigated the errors of measurement due to aspects of the physiology and cooperation of the child. The present study directly assesses this source of measurement undependability for the first time. Investigation of total measurement error variance in 925 recumbent length replicates taken over stasis intervals in growth identifies that between 60% and 70% of total measurement unreliability is due to a child factor undependability. Individual differences are significant and longitudinal growth analyses should consider two to three times the technical error of measurement statistic as a reasonable estimate of the total unreliability for any single measurement of an infant's recumbent length. These results raise issues regarding analytic methods as applied to serial growth data.

Anthropometric measurement error and the assessment of nutritional status

Anthropometry involves the external measurement of morphological traits of human beings. It has a widespread and important place in nutritional assessment, and while the literature on anthropometric measurement and its interpretation is enormous, the extent to which measurement error can influence both measurement and interpretation of nutritional status is little considered. In this article, different types of anthropometric measurement error are reviewed, ways of estimating measurement error are critically evaluated, guidelines for acceptable error presented, and ways in which measures of error can be used to improve the interpretation of anthropometric nutritional status discussed. Possible errors are of two sorts; those that are associated with: (1) repeated measures giving the same value (unreliability, imprecision, undependability); and (2) measurements departing from true values (inaccuracy, bias). Imprecision is due largely to observer error, and is the most commonly used measure of anthropometric measurement error. This can be estimated by carrying out repeated anthropometric measures on the same subjects and calculating one or more of the following: technical error of measurement (TEM); percentage TEM, coefficient of reliability (R), and intraclass correlation coefficient. The first three of these measures are mathematically interrelated. Targets for training in anthropometry are at present far from perfect, and further work is needed in developing appropriate protocols for nutritional anthropometry training. Acceptable levels of measurement error are difficult to ascertain because TEM is age dependent, and the value is also related to the anthropometric characteristics of the group of population under investigation. R > 0.95 should be sought where possible, and reference values of maximum acceptable TEM at set levels of R using published data from the combined National Health and Nutrition Examination Surveys I and II (Frisancho, 1990) are given. There is a clear hierarchy in the precision of different nutritional anthropometric measures, with weight and height being most precise. Waist and hip circumference show strong between-observer differences, and should, where possible, be carried out by one observer. Skinfolds can be associated with such large measurement error that interpretation is problematic. Ways are described in which measurement error can be used to assess the probability that differences in anthropometric measures across time within individuals are due to factors other than imprecision. Anthropometry is an important tool for nutritional assessment, and the techniques reported here should allow increased precision of measurement, and improved interpretation of anthropometric data.

Fatness and body mass index from birth to young adulthood in a rural Guatemalan population

Body mass index (BMI; wt in kg/ht2 in m) has been proposed as a simple and valid measure for monitoring fatness. Using data from a 25-y longitudinal study of rural Guatemalans, we found that, as children, this population was stunted (mean height-for-age z = -2.6) and had low triceps skinfold thicknesses ( approximately 10% of reference medians), yet had mean BMIs above US reference medians. As young adults, mean BMIs were at the 50th and 20th percentiles for women and men, respectively. BMIs between ages 1 and 5 y were moderately correlated (r = 0.2-0.3) with those in young adulthood. BMI was correlated with subscapular (r = 0.5-0.8) and triceps (r = 0.2-0.7) skinfold thicknesses at all ages and with predicted percentage body fat in adolescence (r = 0.65) and adulthood (r = 0.8). Fatness was highly centralized, with ratios of subscapular to triceps skinfold thicknesses at the 50th-90th percentiles of reference medians at all ages. BMI was a poor indicator of central fat; the correlation between BMI and waist-to-hip ratio in 14-17-y-old males was -0.21). In stunted populations in developing countries, BMI alone should be interpreted with caution. In stunted children, BMIs may be high despite small extremity skinfold thicknesses; BMI alone may overestimate the prevalence of fatness in these children. In adults, measures in addition to BMI may be required to identify centralized adiposity in these populations.

The accuracy and reliability of linear measurements of the ulna for anthropometrical studies in dogs

This study investigated the accuracy and reliability of measuring the distance between two surface landmarks (the point of the tuber olecrani and the proximal aspect of the stopper pad) as an indication of ulna length in the live dog. It was found that the chosen skin landmarks did correlate well with the length of the ulna bone. The reliability of such measurements was high when performed by a single person, however this fell to unacceptable levels when multiple people were used to make the measurements. It was concluded that if this technique was to be used in studies to serially record the bone length in live growing dogs, then the measurements should be taken by a single person.

Facial measurements in clinical genetics: How important are the instruments we use?

Prompted by our finding that a popular compendium of clinical measurements often suggests a transparent ruler as a suitable substitute for anthropometric calipers (which were typically used by the original researchers to collect the normative data), we compared facial measurements taken with a ruler and calipers. Our objectives were to compare facial measurement data taken with these instruments by two classes of observer: expert and inexperienced. Ten facial measurements were repeated on four medically normal women by one expert and one inexperienced observer. Both observers' data showed that the caliper-derived means were usually the larger, but, whereas the expert observer's caliper-derived data typically were the least variable, the novice observer had smaller standard deviations and ranges for the ruler-derived data. Statistically significant differences were found between the ruler- and caliper-derived data from both observers on all four subjects, except for subnasale-pogonion and stomion-pogonion. For the novice observer only, endocanthion-endocanthion, left exocanthion-endocanthion, and alare-alare were also nonsignificant. The calibrations of the sliding caliper and ruler were compared to determine if differences between them could explain the statistical results, but were the same. We concluded that the differences between the caliper- and ruler-derived measurements resulted because the ruler often could not be placed directly on the landmarks, as could the arms of the calipers. We recommend that clinicians interested in taking facial measurements to assess their patients consult the original publications for information on the techniques and instruments used so that reliable comparisons with the normative data can be made.

The precision of anthropometric assessment of body fat distribution in children

Precision estimates are given for indices of body mass, fatness and body fat distribution in a sample of n = 19 subjects selected at random from a larger study of cardiovascular disease risk in school-aged children. The value of this study is that little is known about the measurement precision of ratio indices and multivariate constructs of body fat distribution in children or any other age group. Intra- and inter-observer precisions were highest for weight, height, body mass index and six body circumferences (0.95-0.99), and were lower and more variable for five skinfold thicknesses (0.80-0.99). The measurement precision of ratio indices derived from the circumferences (waist/hip and waist/thigh) and the skinfolds (subscapular/thigh and triceps/subscapular) were lower and more variable than precisions of the single variables. Circumference ratio precisions varied from 0.81 to 0.96 and skinfold ratios varied from 0.28 to 0.94. Precisions of a multivariate construct of central fat distribution from five skinfold measures were better (0.77-0.95), suggesting its greater efficacy. Inter-examiner precisions tended to be significantly lower than intra-examiner precisions for skinfold thicknesses and all composite indices. The lower precisions of ratio indices, compared to the measurement accuracy of the variables which make them up, needs to be considered in epidemiological studies of body fat distribution.

Brief communication: measurement size, precision, and reliability in craniofacial anthropometry: bigger is better

In this paper we examine the results of an intraobserver measurement error study involving 49 craniofacial variables that ranged in size from less than 1 cm to approximately 20 cm. Repeat measurements were taken on 10 male and 10 female adult subjects (19-59 years old). Our focus is on the relationship between measurement size and measurement error across the 49 variables. We found that the size of the variable showed no relationship with the magnitude of the error as measured by the technical error of measurement. When the error was expressed as a coefficient of relative variation (Malina et al.: Vital and Health Statistics, Series 11, No. 23. Washington, DC: US Department of Health and Human Services, 1973), this quantity was negatively associated with the size of the measurement. Conversely, reliability (Fleiss: The Design and Analysis of Experiments. New York: John Wiley & Sons, 1986) was positively correlated with measurement size. We did not find effects of scale (Marks et al.: Am. J. Epidemiol. 130:578-587, 1989) within the individual measurements. Thus, for the range of size of the craniofacial measurements in this study, measurement size must be added to the list of factors such as ease of locating landmarks, measurement technique, and systematic bias in the application of the technique that can affect precision and reliability in anthropometry.

Saltation and stasis: a model of human growth

Human growth has been viewed as a continuous process characterized by changing velocity with age. Serial length measurements of normal infants were assessed weekly (n = 10), semiweekly (n = 18), and daily (n = 3) (19 females and 12 males) during their first 21 months. Data show that growth in length occurs by discontinuous, aperiodic saltatory spurts. These bursts were 0.5 to 2.5 centimeters in amplitude during intervals separated by no measurable growth (2 to 63 days duration). These data suggest that 90 to 95 percent of normal development during infancy is growth-free and length accretion is a distinctly saltatory process of incremental bursts punctuating background stasis.

Evaluation of the metrecom and its use in quantifying skeletal landmark locations

Several factors can be involved in evaluating a motion analysis system. The purposes of this study were to evaluate: 1) the accuracy, repeatability, and linearity of the Skeletal Analysis System (Metrecom System) and 2) the reliability of bony landmark identification with a method using the Metrecom Skeletal Analysis System (Metrecom Method) to obtain coordinates for human skeletal landmarks. A calibration control object with 20 known three-dimensional coordinates in a rectangular field was used as the gold standard for evaluating the Metrecom System for measuring X, Y, and Z spatial coordinates. The Metrecom Method was then evaluated using a test-retest approach for 10 bony landmarks on each of 10 normal subjects examined by two different examiners. Relative to the Metrecom System, the results demonstrated that the hysteresis was minimal (1.8 mm), and linearity was excellent. The differences between the true and measured distances for the 20 known points were not statistically significant (p >/= .05). The variability for any point within the field of measurement was homogeneous (p </= .05). The accuracy (average difference between known and measured points) of the Metrecom System was found to be 2.7 mm. Repeatability in terms of the stability of the Metrecom System as indicated by deviations along the X, Y, and Z axes was .22, .57, and .31 mm, respectively. The results involving the Metrecom Method showed that the intraexaminer and interexaminer differences were not statistically significant (p >/= .05). The mean intrarater reliability (ICC) for identification of coordinates for 10 bony landmarks was .95 for one examiner and .96 for the other examiner. The mean interrater ICC was .87, with all coefficients being above .80. In conclusion, use of the Metrecom System is affected by controllable human factors, in which case valid and reliable measurements for skeletal landmarks can be obtained. J Orthop Sports Phys Ther 1992;16(4):182-188.

Nutrition promotion: the role of monitoring physical growth

Growth monitoring has been included as one of the basic strategies for child survival. In this paper, the rationale for this is reiterated both for individual as well as population nutritional surveillance. Methods for and approaches to growth monitoring are described. In addition, potential problems in implementing growth monitoring projects and interpreting the results are discussed. Despite its lack of sensitivity and specificity as a diagnostic tool, its advantages in terms of low cost, simplicity, reliability and social acceptability justify its use in nutritional surveillance, particularly in populations at risk of malnutrition.

Maternal supplementation and bone growth in infancy

The effects of maternal supplementation during pregnancy and lactation on bone growth of infants were investigated in 272 mother-infant pairs who participated in the Guatemalan Longitudinal Study of Nutritional Supplementation, Growth and Development. Mothers received one of two nutritional supplements according to village of residence, and bone growth was determined from dimensions of the second metacarpal measured directly from hand-wrist radiographs of 3-month-old infants. Multiple regression analyses indicated significant supplementation effects on cortical bone dimensions related to the volume of supplement intake. These findings were independent of maternal characteristics and attendance at the supplementation centres, and the infant's gender, size, gestational age and morbidity experience. The nutrient composition of the supplements and the patterns of the supplementation effects eliminate proteins, energy, calcium and phosphorus as the nutrients potentially responsible for the bone-specific response. Candidate nutrients for the observed effects are vitamin A, ascorbic acid, niacin, thiamin, iron or fluorine. Presumptive evidence suggests the effects may be due to vitamin A supplementation. These findings suggest opportunities for nutritional intervention in pregnancy and the early postpartum period to prevent osteopaenia in infancy.

Meaning of biodistance statistics: a test case using adult monozygotic twins

Anthropometry, historically one of the primary research techniques in physical anthropology, has been widely utilized in biodistance studies. The complex genetic and environmental interaction that governs the expression of anthropometric dimensions, together with concerns over measurement error, have sometimes clouded the interpretation of biodistances based upon anthropometry. In this study, 51 pairs of adult monozygotic twins were analysed using discriminant analysis and Mahalanobis' generalized distance. Both male and female twins, grouped by first- versus second-born, displayed very small, statistically insignificant distances between groups. When literature estimates of intra-observer measurement errors were used as a frame of reference, the average absolute differences between the twin pairs were approximately twice the size of the measurement error estimates. The results of this study suggest that, first, the environmental effect upon the genetically influenced traits measured by anthropometry is not large enough to bring about significant multivariate differences between identical twin pairs; and, second, biodistance studies based upon anthropometry can be reliable so long as measurement error is minimized.

Reliability of anthropometric methods and replicate measurements

The Spearman-Brown Prophesy formula, derived from psychometrics, may be used in anthropometric studies to describe the relationship between the intraclass reliability coefficient for a single measurement and the reliability resulting from the mean of replicate measurements. This theory may be applied to determine expected reliabilities of anthropometric protocols using replicate measurements and to determine the numbers of replicate measurements necessary to achieve desired levels of reliability.

Measurement error in clinical perinatal data

The error measurement of clinical perinatal variables obtained during the standardization and data-collection periods of a large prospective epidemiologic study is presented. The error is considerably larger during the data-collection period, particularly with regard to uterine height, birth weight, and blood pressure values. This information strongly supports the need to continuously supervise and monitor perinatal data collection systems, even after standardization.

Relative reliability of circumferences and skinfolds as measures of body fat distribution

The question has arisen whether patterns of body fat distribution can be identified by body circumferences, a method which is said to be more reliable and simpler than skinfold thickness or like measures of subcutaneous fat (Ashwell et al., Int. J. Obes. 6: 143-152, 1982). Here we address the question of whether body circumferences are inherently more reliable than skinfold thicknesses in 77 intra- and 224 interexaminer replicates from the Health Examination Survey of 12 to 17-year-olds in the U.S.A. Reliability of six body circumferences (0.96) was significantly (P less than .01) higher than that of skinfold thicknesses at five sites (0.91), suggesting that circumferences are a more reliable method. However, the reliability of skinfolds is still high, and skinfolds may be used in studies which focus on preadults or other groups in which the validity of circumferences as measures of body fat distribution is unknown.

Measurement error and reliability in four pediatric cross-sectional surveys of cardiovascular disease risk factor variables--the Bogalusa Heart Study

Four cross-sectional epidemiologic studies of children 5-17 years of age were conducted between 1973 and 1982 in the community of Bogalusa, La. Anthropometric, blood pressure and serum lipid variables were measured. Measurement error (precision) and reliability (reproducibility) were estimated for these risk factor variables of coronary artery disease. Precision was less than 0.8 cm for height, 0.8 kg for weight, and 1 mm for triceps and subscapular skinfold over the four surveys. Measurement error for the mercury sphygmomanometer and automatic blood pressure instruments was between 4 and 5 mmHg during this same period. Except for triglycerides and total and alpha-lipoprotein cholesterols that stabilized at lower levels after the first survey, precision of laboratory variables remained nearly constant over the 9 years of survey. Anthropometric measurements were found to be the most reliable followed next by the laboratory and then blood pressure measurements. These estimates offer guidelines applicable to data collection and processing in future investigations of risk factor variables for coronary artery disease.

Interobserver reliability of skinfold measurements in infants and young children

Interobserver reliabilities were determined for the triceps, biceps, subscapular, suprailiac, and abdominal skinfolds in 77 children, 9-24 months of age. Technical errors of measurement (replicate variances) and coefficients of variation were compared to data on 12-17-year-olds from the U.S. Health Examination Survey (HES) to 2.5-7-year-old Guatamalan children. Of the five skinfolds, the between-observer variation was not significantly different from zero in four; in the case of the biceps fold, F-ratio was significant at p less than .01. Errors of measurement are less for these data than for the HES or Guatemalan studies. This difference is attributed to the larger means of the older children and youth, as well as to the greater error of measurement shown to exist for larger skinfolds.

Postnatal growth of intrauterine growth retarded infants

205 single, term newborns were followed up to their first birthdays. Each was classified as intrauterine growth retarded (IUGR) (59), or adequate birth weight (ABW) (146), and further subdivided by their individual ponderal index at birth (PI). By the end of their first year the IUGR infants had not reached the weight and length of their normal counterparts. Those with low PI obtained adequate PI values by the third month; IUGR infants with adequate PI at birth remained shorter and lighter but with adequate PI throughout the first year of life. The catch-up process in the IUGR infants with low PI can be explained by a higher growth velocity in weight, triceps and subscapular skinfolds apparent during the first trimester of postnatal life. The limitations of using PI as a tool to monitor the growth patterns of a heterogenous group of IUGR infants are discussed.

On error due to graduation of scaling for anthropometry

It is shown that the measurement error due to graduation of scaling for anthropometric variables usually follows a uniform distribution. The result is used to investigate to what extent graduation in anthropometric scales affects th short-term intrasubject variance. It is seen that for commonly used graduations the effect is not to be considered substantial.

Relationship of maternal and infant nutrition to infant growth

A cohort of all infants born between January 1, 1969 and February 28, 1977 in four rural villages in Eastern Guatemala which were participating in a longitudinal project of nutrition and mental development was studied. As part of the study, prospective information on anthropometric measurements, morbidity, dietary intake and socioeconomic and cultural characteristics was collected. In addition, two types of food supplements were distributed: calorie and protein-calorie. Attendance at the feeding centers in each village and the amount of supplements consumed by children and pregnant and lactating mothers were recorded daily. We studied the effect of the supplements consumed by the mother during pregnancy and lactation and by the infant on trimestral infant weight and length changes during the first year of life. The data indicate that infant calorie supplementation before three months of age is significantly and negatively associated with infant growth; after three months of age, supplemental calories consumed by the infant are significantly and positively associated with infant weight and length gains. In addition, a small positive association was found between maternal caloric supplementation during lactation and infant growth during the first two trimesters of life, after controlling for potentially confounding factors for which data are available in this study.

Blood pressure, fatness, and fat patterning among USA adolescents from two ethnic groups

Many studies have explored the relationship between blood pressure and body size and composition in adults and preadults, but none has inquired into the relationship of blood pressure and the anatomical distribution of subcutaneous fat (fat patterning). Fat patterning has an association with chronic diseases (diabetes and cardiovascular disease) in adults. We sought the relationship between fatness, fat patterning, weight, and height among adolescents (12 to 17 years of age) of two ethnic groups (black and white) from the Health Examination Survey. Systolic blood pressure adjusted for age was related to body build variables in all sex/ethnic groups in decreasing order of importance as follows: body weight (independent of height), fatness (as assessed by a two skinfold index), and an excess of fat on trunk relative to fat on the leg (pattern index). Neither fatness nor fat patterning was significantly related to blood pressure after weight entered the regression equation. Relative fat patterning may be less important in predicting cardiovascular risk factors in adolescents than it is in adults. The fact that body weight was more important than fatness suggests that the weight/blood pressure association is due to components of body mass other than body fat.

Genetic-environmental interactions in physical growth

Variability in stature among young children is often ascribed to health and nutrition differences in malnourished populations and to genetic differences in well-nourished populations. Hence, it was hypothesized that parent-child correlations in malnourished Guatemalan populations would be markedly lower than those reported for European samples. Instead, it was found that parent-child and sibling correlations were similar in both kinds of populations. The simplest interpretation of these results is that variability in stature among malnourished children is as much as reflection of genetic differences as in developed nations. However, explanations can also be advanced which would attribute the higher than expected correlations to the environment. For instance, it could be that socioeconomic and nutritional status is correlated across generations. In other words, parents who had relatively better conditions as children are more likely to provide a better environment for their children. Consequently, the relative contribution of genetics and environment to variability in height is still unsettled. Nonetheless, it appears that variability in body size in malnourished populations, regardless of the relative importance of its causes, is a useful indicator of health and nutrition.

Office assessment of nutritional status

The standard components of nutritional assessment-anthropometry, clinical examination, dietary intake, and biochemical analysis--have been discussed in the context of "office or clinic practice." With appropriate modifications of these tehcniques, nutritional assessment can become a basic and integral part of pediatric care.

Diarrheal diseases and growth retardation in preschool Guatemalan children

The relationship between diarrheal diseases and growth increments in total body length and weight was investigated in 716 rural Ladino Gautemalan children. Data on diarrheal diseases were provided by the mothers through retrospective surveys carried out at 14-day intervals. Increments in length and weight, semestral from near birth at four years and yearly thence to seven, were related to days ill with diarrheal diseases during the same time interval. Because the data here reported were collected over a two year period, a child may have had information for more than one period. In total, 1,343 child periods were investigated. Days ill with diarrheal diseases were found to be significantly associated with reduced growth in length and weight. It was assumed that the average differences in growth by seven years of age between children in the present sample and children from well-to-do societies, are mainly a function of environmental differences and consequently, a measure of the extent of growth retardation. By expressing the growth retardation specifically associated with diarrheal diseases as a fraction of the above differences it was then estimated that around 10% of this growth retardation was associated with diarrheal diseases.