Evaluation of Foot Structure in Preschool Children Based on Body Mass.

BACKGROUND The human foot has a complex structure and the ligamentous and muscular apparatus undergoes transformation and adaptation during its ontogenetic development. Excessive body mass may be one of the factors disrupting proper foot formation. This study aimed to assess the foot structure in preschool children in relation to body mass. MATERIAL AND METHODS A total of 105 children aged 6.27±0.60 years were examined. Height, weight, and segmental body composition were determined using the Tanita MC-780 body composition analyzer. The foot structure was assessed using the Kasperczyk method, supplemented with digital analysis using the Podoscan 2D camera. The Weisflog index and gamma angle for feet were calculated. Children were divided into 2 groups: children in Group I did not have foot deformities and those in Group II had foot deformities. RESULTS No correlation was observed between body mass and the occurrence of anomalies in foot structure. A correlation was noted between the Weisflog index for the right foot and height in both groups. The Weisflog index for both feet was correlated with BMI, with higher values obtained for the left foot in both groups. In Group II, a correlation was observed between the gamma angle value for the left foot and the predicted muscle mass for the right lower limb, as well as between the same foot and the predicted muscle mass for the left lower limb. CONCLUSIONS No correlation was observed between high BMI and the occurrence of anomalies in foot structure. A relationship was identified between muscle mass and foot structure.

Association between standing height and physical disability among U.S. adults aged 60 years and older: findings from NHANES 2015-2018.

BACKGROUND: Physical disability is an important cause of affecting the quality of life in the elderly. The association between standing height and physical disability is less studied. PURPOSE: The purpose of this study is to investigate the possible link between standing height and physical disability among U.S. adults aged 60 years and older. METHODS: The cross-sectional data were obtained from the US National Health and Nutrition Examination Survey (NHANES) 2015-2018. Physical disability was assessed by six questions: "Have serious difficulty hearing (SDH)?", "Have serious difficulty seeing (SDS)?", "Have serious difficulty concentrating (SDC)?", "Have serious difficulty walking (SDW)?", "Have difficulty dressing or bathing (DDB)?" and "Have difficulty doing errands alone (DDEA)?". Responses to these questions were "yes" or "no". Answer yes to one of the above six questions was identified as physical disability. Standing height (cm) was measured with an altimeter. Multivariate logistic regression was performed to examine the possible link between standing height and physical disability after adjustment for all covariates. RESULTS: A total of 2624 participants aged ≥ 60 years were included in our study, including 1279 (48.7%) females and 1345 (51.3%) males. The mean age of participants was 69.41 ± 6.82 years. After adjusting for all potential confounders, the inverse relationship between standing height and all physical disability (APD) was statistically significant (OR = 0.976, 95%CI:0.957-0.995). In addition, among six types of physical disability (SDH, SDS, SDC, SDW, DDB, DDEA), standing height was also a protective factor for SDW (OR = 0.961, 95%CI:0.939-0.983) and DDEA (OR = 0.944, 95%CI:0.915-0.975) in the full-adjusted model. CONCLUSION: The cross-sectional population based study demonstrates that standing height is a protective factor for physical disability among U.S. adults aged 60 years and older.

The relationships between optimal infant feeding practices and child development and attained height at age 2 years and 6-7 years.

Limited evidence exists on the long-term effects of early feeding practices on child growth and development. We examined the relationships between infant feeding practices and child height and development at ages 2 and 6-7 years. We studied 885 mother-child dyads from a randomized controlled trial of preconception supplementation in Vietnam. Early initiation of breastfeeding (EIBF), exclusive breastfeeding (EBF), breastfeeding (BF) duration and minimum dietary diversity (MDD) were assessed using World Health Organization (WHO) guidelines. Child development was assessed by the Bayley Scales of Infant Development-III at 2 years and the Wechsler Intelligence Scale for Children® - IV at 6-7 years. Child height-for-age z-score (HAZ) was calculated from child height and age. Multivariable regression and structural equation models were used in analyses that controlled for confounding. EIBF and EBF at 6 months occurred in 52% and 62% of children, respectively. Mean breastfeeding duration was 18 months and 83% achieved MDD at 1 year. EIBF was associated with motor (ß = 0.13, 95% confidence interval [CI]: 0.00, 0.28) and cognitive development at 2 years (ß = 0.12, 95% CI: -0.01, 0.26), which in turn were positively associated with cognitive development at 6-7 years. EBF was directly associated with development at 6-7 years (ß = 0.21, 95% CI:0.08, 0.34) whereas motor and cognitive development at 2 years explained 41%-75% of the relationship between EIBF and development at 6-7 years. HAZ at 2 years also mediated 70% of the association between MDD at 1 year and HAZ at 6-7 years. BF duration was not associated with child development and HAZ. Early infant feeding practices, especially EIBF and EBF, have important long-term implications for optimizing child linear growth and cognition as they begin school.

Normative Standards for Isokinetic and Anthropometric Classifications of University-Level Netball Players.

CONTEXT: The purpose of the study was to develop normative ranges and standards for knee and shoulder isokinetic and anthropometric values. These standards can be qualitatively interpreted and allow practitioners to classify isokinetic and anthropometric values more objectively for university-level netball players. DESIGN: Posttest only observational study design. All players were only evaluated once during the in-season to generate normative ranges. METHODS: A total of 51 female players volunteered. Participants were evaluated on an isokinetic dynamometer at 60° per second to obtain knee-extensor and knee-flexor values as well as shoulder-flexor and shoulder-extensor values. A total of 16 anthropometric variables were collected including stature, body mass, 8 skinfolds, and 6 circumferences. Between-group differences were calculated to determine whether playing level was a differentiating factor in data. RESULTS: Normative standards were developed for isokinetic parameters associated with the knee and shoulder joints as well as skinfolds and circumference measures. No statistically significant between-group differences were evident (χ2Kruskal-Wallis[2] = 3.96, P = .140). CONCLUSION: These standards can be used by coaches and practitioners to set attainable goals for individual players or those from secondary leagues, classify individual and team-based performances, and facilitate decision-making processes.

Correspondence on "Sex steroid priming for growth hormone stimulation testing in children and adolescents with short stature: A systematic review".

Duncan et al. reviewed the response to growth hormone stimulation testing after priming in peripubertal children. The concern is that there is little research documenting the response to growth hormone treatment in patients with sex hormone primed growth hormone stimulation testing and those unprimed. The controversy about priming or not can be summarized as follows: if one wants to know if the production of growth hormone during puberty will be adequate in terms of peak growth hormone responses then stimulation with priming should be done.

An increase in the developmental tempo affects the secular trend in height in male Austrian conscripts birth cohorts 1951-2002.

OBJECTIVES: Using population-based data on height in Austria from birth cohort 1951 to 2002, we aim to evaluate the secular trends in height and developmental tempo among Austrian young men. METHODS: Data were obtained from the Austrian conscription medical examination. We included 1 205 112 conscripts (18-<20 years) who were born between 1951 and 2002 and 853 645 conscripts (17-<19 years) who were born between 1961 and 2002. Height was measured during the medical examination and was used to evaluate the secular trends of mean height over time. Furthermore, the mean difference in height between conscripts of 17- and 18 years old were compared across birth cohorts. RESULTS: The mean height of conscripts aged 17 years increased by 2.2 cm (p < .0001) in between 1961 and 2002. The mean height of conscripts aged 18 years increased by 4.3 cm (p < .0001) between 1951 and 2002. However, the increase in mean height has slowed down since the 1970 s. The difference in mean height between 17 and 18 years old widened from about 0.1 cm in 1961 to 0.3 cm around 1970 and then steadily narrowed again to 0.1 cm at the end of the study period. CONCLUSIONS: The increasing trend in height slows at the end of the 20th century, the developmental tempo at the population level, however, continued to increase. The difference in mean height between 17 and 18 years old narrowed, which may indicate that young men reached their final height earlier.

Body composition in preschool children with short stature: a case-control study.

BACKGROUND: Short stature is defined as height below 2 standard deviations of the population with the same age, gender. This study is aimed to assess the characteristics of body composition in preschool children with short stature. METHODS: Anthropometric measurements and body composition were assessed in 68 preschool children aged 3 to 6 years old with short stature and 68 normal controls matched on age and gender. Height, weight and body composition (total body water, protein, minerals, body fat mass, fat-free mass, soft lean mass, skeletal muscle mass, and bone mineral contents) in the two groups were measured and compared. RESULTS: The total body water, protein, minerals, body fat mass, fat-free mass, soft lean mass, skeletal muscle mass, and bone mineral contents were lower in preschool children with short stature than controls (P < 0.05). Body mass index and fat mass index did not differ between groups. Fat-free mass index was significantly lower in short stature group than controls (t = 2.17, P = 0.03). Linear regression analysis showed that there was a positive correlation between height and fat-free mass index [ß, 1.99 (0.59, 3.39), P = 0.01], a negative correlation between height and body fat percentage [ß, - 0.20 (- 0.38, - 0.01), P = 0.04]. The proportions of fat-free mass in the upper limbs were significantly lower (Right,t = - 2.78,Left t = - 2.76, P < 0.05, respectively) in short stature, although body fat distribution was not. CONCLUSIONS: The fat-free mass such as protein and bone minerals is lower in preschool children with short stature, suggesting the monitoring of fat-free mass for early identification and intervention.

Preliminary results of two novel devices for epiphysiodesis in the reduction of excessive predicted final height in tall stature.

BACKGROUND: In the treatment of tall stature, the reduction of excessive predicted final height can either be achieved by hormonal treatment or surgically by temporary (tED) or permanent (pED) epiphysiodesis. The present study evaluates the preliminary results of two novel devices for tED and pED around the knee to reduce the predicted final height. MATERIALS AND METHODS: A retrospective analysis was performed to evaluate the clinical and radiographic outcome after bilateral epiphysiodesis for the treatment of tall stature. A cohort of 34 patients (16 girls, 18 boys) who underwent either tED or pED between 2015 and 2020 were eligible for analysis based on the electronic patient records and picture archiving and communication system of our orthopaedic teaching hospital. tED was conducted in 11 patients (32%) through bilateral implantation of four RigidTacks™ (Merete, Berlin, Germany) around the knee. Twenty-three patients (68%) received pED, performed with an EpiStop™ trephine (Eberle, Wurmberg, Germany). The mean overall follow-up time was 2.9 years. RESULTS: The mean age at surgery was 12.3 years in girls and 13.2 years in boys. Patients had a mean body height of 175.2 cm in girls and 184.7 cm in boys at surgery. The mean predicted final height was 191.4 cm in girls and 210.4 cm in boys. At the last follow-up, 26 patients (76.5%) had achieved skeletal maturity. The mean height of skeletally mature patients was 187.2 cm in girls and 198.5 cm in boys. A mean reduction of the predicted final height of 5.9 cm in girls and 8.7 cm in boys was achieved, corresponding to a reduction in remaining growth of 46% in girls and 38% in boys. Secondary frontal plane deformities of the knee were detected in 5/11 patients (45.5%) in the tED group and 1/23 treatments (4.3%) in the pED group. CONCLUSIONS: tED and pED have both proven to be efficient at achieving growth inhibition to reduce excessive predicted height. However, tED has been associated with an increased risk of secondary angular deformities of the knee. Furthermore, the risk of implant-related complications and the necessity of a subsequent surgical intervention for implant removal have led our study group to abandon tED when treating tall stature. Long-term results of both procedures are pending.

Association between family history, early growth and the risk of beta cell autoimmunity in children at risk for type 1 diabetes.

AIMS/HYPOTHESIS: The aim of this work was to examine the relationship between family history of type 1 diabetes, birthweight, growth during the first 2 years and development of multiple beta cell autoantibodies in children with a first-degree relative with type 1 diabetes and HLA-conferred disease susceptibility. METHODS: In a secondary analysis of the Trial to Reduce IDDM in the Genetically at Risk (TRIGR), clinical characteristics and development of beta cell autoantibodies were compared in relation to family history of type 1 diabetes (mother vs father vs sibling) in 2074 children from families with a single affected family member. RESULTS: Multiple autoantibodies (≥2 of 5 measured) developed in 277 (13%) children: 107 (10%), 114 (16%) and 56 (18%) born with a mother, father or sibling with type 1 diabetes, respectively (p < 0.001). The HR for time to multiple autoimmunity was 0.54 (95% CI 0.39, 0.75) in offspring of affected mothers (n = 107/1046, p < 0.001) and 0.81 (95% CI 0.59, 1.11) (n = 114/722, p = 0.19) in offspring of affected fathers, compared with participants with a sibling with type 1 diabetes (comparator group n = 56/306). The time to the first autoantibody present (to insulin, GAD, tyrosine phosphatase-related insulinoma-associated 2 molecules, islet cell or zinc transporter 8) was similar in the three groups. Height velocity (z score/year) in the first 24 months was independently associated with developing multiple antibodies in the total cohort (HR 1.31 [95% CI 1.01, 1.70], p = 0.04). A higher birthweight in children born to an affected mother vs affected father or an affected sibling was not related to the risk of multiple autoimmunity. CONCLUSIONS/INTERPRETATION: The risk of developing multiple autoantibodies was lower in children with maternal type 1 diabetes. For the whole group, this risk of developing multiple autoantibodies was independent of birthweight but was greater in those with increased height velocity during the first 2 years of life. However, the risk associated with paternal type 1 diabetes was not linked to differences in birthweight or early growth. TRIAL REGISTRATION: ClinicalTrials.gov NCT00179777 Graphical abstract.

Effect of Correcting the Postnatal Age of Preterm-Born Children on Measures of Associations Between Infant Length-for-Age z Scores and Mid-Childhood Outcomes.

Child growth standards are commonly used to derive age- and sex-standardized anthropometric indices but are often inappropriately applied to preterm-born children (<37 weeks of gestational age (GA)) in epidemiology studies. Using the 2004 Pelotas Birth Cohort, we examined the impact of correcting for GA in the application of child growth standards on the magnitude and direction of associations in 2 a priori-selected exposure-outcome scenarios: infant length-for-age z score (LAZ) and mid-childhood body mass index (scenario A), and infant LAZ and mid-childhood intelligence quotient (scenario B). GA was a confounder that had a strong (scenario A) or weak (scenario B) association with the outcome. Compared with uncorrected postnatal age, using GA-corrected postnatal age attenuated the magnitude of associations, particularly in early infancy, and changed inferences for associations at birth. Although differences in the magnitude of associations were small when GA was weakly associated with the outcome, model fit was meaningfully improved using corrected postnatal age. When estimating population-averaged associations with early childhood growth in studies where preterm- and term-born children are included, incorporating heterogeneity in GA at birth in the age scale used to standardize anthropometric indices postnatally provides a useful strategy to reduce standardization errors.

Changes in weight and height among Chinese preschool children during COVID-19 school closures.

BACKGROUND AND OBJECTIVES: COVID-19-related school closures may increase the prevalence of childhood obesity, which has aroused public concerns. We aimed to analyze the weight and height changes in Chinese preschool children during the COVID-19-related school closures period. METHODS: A total of 124,603 children from multi-city kindergartens in China were included in this study. We evaluated the prevalence of overweight and obese in preschool children experienced school closures, and compared the changes in BMI, weight, and height of preschool children among COVID-19 school closures period, the same period last year and the same period the year before last. RESULTS: After the school closures, childhood obesity prevalence increased, whereas overweight prevalence decreased. During school closures, the average increase in height was about 1 cm less as compared with the same period last year and the year before last, but no noteworthy difference in the weight change was observed among the three periods. CONCLUSIONS: During COVID-19 school closures, children's height increase seemed to be more affected than weight change. Innovative, robust, and highly adaptable strategies should be taken to increase physical activity, reduce sedentary time and promote healthy diets, to minimize the adverse impact of school closures.

The effect of height on estimates of the change in BMI-based prevalence of childhood obesity.

BACKGROUND/OBJECTIVES: Body mass index (BMI, body mass/height2) is biased toward height in children. Here we investigate how change in population height affected change in BMI-based estimates of the prevalence of overweight and obesity in Australian children. SUBJECTS/METHODS: Height, weight, and percent body fat (%BF) were measured at ages 8, 10, and 12 years (1855 sets of measures). Age-specific relationships between BMI and height were derived, adjusting for %BF, to estimate the degree of height bias inherent in BMI. Then, from cross-sectional measurements recorded in 1985 (N = 2388) and 1995 (N = 2148) in 8, 10, and 12 year olds, changes in overweight/obesity prevalences were calculated before and after accounting for the BMI-height bias. RESULTS: Estimates of the effect of height on BMI following adjustment for %BF were similar across age groups and all were significant at p < 0.001. Referring to 12 year olds, at the same %BF for a 1% increase in height there was 0.77% (95% CI 0.55, 0.99) increase in BMI in boys, and 0.74% (0.28, 1.02) increase in girls. Between 1985 and 1995, mean height of 12-year-old boys and girls increased 3.9 and 3.2 cm, respectively. In 1985 unadjusted prevalences of combined overweight/obesity in boys and girls were 13.5% and 13.0%, respectively, and in 1995 were 24% and 24.5%. The latter values were reduced to 21.6% and 22.6% after adjusting for increased height. CONCLUSIONS: Previously reported increases in childhood overweight/obesity in Australia between 1985 and 1995 were likely to be moderately overestimated as a result of increased population height; suggesting that population height be taken into account in any pediatric investigation of changes in overweight/obesity prevalence over time.

Overweight and obesity at age 19 after pre-natal famine exposure.

BACKGROUND: Weight for height has been used in the past as an indicator of obesity to report that prenatal exposure to the Dutch famine of 1944-1945 determined subsequent obesity. Further evaluation is needed as unresolved questions remain about the possible impact of social class differences in fertility decline during the famine and because being overweight is now defined by a Body Mass Index (BMI: kg/m2) from 25 to <30 and obesity by a BMI of 30 or more. METHODS: We studied heights and weights of 371,100 men in the Netherlands born between 1943 and 1947 and examined for military service at age 19. This group includes men with and without prenatal exposure to the Dutch famine. RESULTS: There was a 1.3-fold increase in the risk of being overweight or obese in young adults at age 19 after prenatal famine exposure in early gestation. The increase was only seen in sons of manual workers born in the large cities of Western Netherlands and not among those born in smaller cities or rural areas in the West. Social class differentials in fertility decline during the famine did not bias study results. CONCLUSIONS: The long-term adverse impact of prenatal famine on later life type 2 diabetes and mortality through age 63 is already showing at age 19 in this population as a significant increase in overweight risk.

Quantifying childhood fat mass: comparison of a novel height-and-weight-based prediction approach with DXA and bioelectrical impedance.

Accurate assessment of childhood adiposity is important both for individuals and populations. We compared fat mass (FM) predictions from a novel prediction model based on height, weight and demographic factors (height-weight equation) with FM from bioelectrical impedance (BIA) and dual-energy X-ray absorptiometry (DXA), using the deuterium dilution method as a reference standard. FM data from all four methods were available for 174 ALSPAC Study participants, seen 2002-2003, aged 11-12-years. FM predictions from the three approaches were compared to the reference standard using; R2, calibration (slope and intercept) and root mean square error (RMSE). R2 values were high from 'height-weight equation' (90%) but lower than from DXA (95%) and BIA (91%). Whilst calibration intercepts from all three approaches were close to the ideal of 0, the calibration slope from the 'height-weight equation' (slope = 1.02) was closer to the ideal of 1 than DXA (slope = 0.88) and BIA (slope = 0.87) assessments. The 'height-weight equation' provided more accurate individual predictions with a smaller RMSE value (2.6 kg) than BIA (3.1 kg) or DXA (3.4 kg). Predictions from the 'height-weight equation' were at least as accurate as DXA and BIA and were based on simpler measurements and open-source equation, emphasising its potential for both individual and population-level FM assessments.

Clinical charts for surveillance of growth and body proportion development in achondroplasia and examples of their use.

Clinical surveillance of infants and children with achondroplasia necessitates syndrome-specific charts due to extreme short stature with deviating body proportions. Height, arm span and leg length develop far below normal population ranges. We present growth and body proportion charts for ages 0-20 years, constructed from semi-longitudinal standardized measurements of about 450 children, along with some examples of achondroplasia typical and atypical growth pattern. We combine head circumference, height and weight for 0-4 years into one (infancy) page and height and weight for 4-20 years in another (childhood-adolescence) using nonlinear axes to account for the rapidly decreasing growth velocity. Similarly, weight and BMI are based on nonlinear axes to balance wide SD-channels at higher and narrow SD-channels at lower levels of weight/BMI. Charts for following sitting height, sitting height/height ratio, arm span, leg and foot length are also presented. Clinical examples illustrating the applicability of the charts include cases of extreme prematurity, extreme head circumference development before and after shunting, achondroplasia complicated by chromosomal or additional genetic abnormality and by growth hormone deficiency as well as of evaluating growth promoting therapy.

Independent associations of women's age at marriage and first pregnancy with their height in rural lowland Nepal.

OBJECTIVES: In many South Asian communities, the majority of women are married during adolescence and reproduce before 20 years. Early reproduction may adversely affect maternal nutrition and linear growth, however whether early marriage has similar effects is unknown. Shorter women might also be preferentially chosen for earlier marriage. We hypothesized that early marriage and early pregnancy may each be associated with women's shorter height, independent of any selection effects. MATERIALS AND METHODS: We analyzed cross-sectional data on 7,146 women aged 20-30 years from rural lowland Nepal. Linear regression models tested associations of early marriage and early reproduction with height, adjusting for women's education and husbands' characteristics (education and wealth) that might index preferential selection of short young women for marriage. RESULTS: Median ages at marriage and first pregnancy were 15 and 18 years, respectively, with 20% pregnant <16 years. Both early marriage and early pregnancy were independently associated with shorter stature, accounting for a decrement of 1.4 cm, which decreased to 1 cm after adjusting for women's education. Effects of early marriage and reproduction persisted after adjusting for the tendency of poorer and less educated men to marry young and short women, indicating a role for social selection. DISCUSSION: The decrements in height associated with early marriage and reproduction are indicative of broader adverse effects on maternal metabolism during a "critical period" of growth and maturation in the life-course of women. Although the magnitudes of effect are relatively small, they affect large numbers of women in this population.

Association of gestational diabetes mellitus with offspring weight status across infancy: a prospective birth cohort study in China.

BACKGROUND: The association between gestational diabetes mellitus (GDM) and childhood body weight remains controversial, and additional study is needed, especially in Asian populations. METHODS: This prospective study investigated the association between maternal glucose concentration, and GDM status and infant body weight from birth to 12 months of age. Linear mixed effects (LME) models and multiple linear regression were used to assess the longitudinal association of GDM with infant growth measured by weight-for-length z-scores (WFLZ), weight-for-age z-scores (WFAZ), and length-for-age z-scores (LFAZ) at birth, 1, 3, 6, 8, and 12 months of age. RESULTS: Offspring born to mothers with GDM had higher WFLZ [ß: 0.26 SD units (95% CI: 0.13-0.40)] across infancy than those of mothers without GDM. When stratified analysis by maternal pre-pregnancy body mass index (BMI) status, the association was pronounced in normal-weight [ß:0.28 SD units (95% CI: 0.11-0.45)] and overweight/obese women [ß: 0.34 SD units (95% CI: 0.09-0.58)] but not in underweight women (P for interaction < 0.05). Multiple linear regression found that the effect estimate of GDM on infant WFLZ was highest at birth [ß: 0.36 SD units (95% CI: 0.11-0.61)], remained significant at 1 [ß: 0.22 SD units (95% CI: 0.03-0.41)] and 3 [ß:0.19 SD units (95% CI: 0.01-0.37)] months of age and decreased across infancy. Maternal GDM status was not associated with infant WFAZ or LFAZ. CONCLUSIONS: Maternal GDM status was associated with infant WFLZ, but not WFAZ or LFAZ. The association between GDM status and offspring WFLZ was more pronounced in early infancy or in normal-weight and overweight/obese women. Increased public health efforts to prevent GDM in normal-weight and overweight/obese pre-pregnancy mothers are recommended to control offspring overweight or obesity.

Genetic instrumental variable regression: Explaining socioeconomic and health outcomes in nonexperimental data.

Identifying causal effects in nonexperimental data is an enduring challenge. One proposed solution that recently gained popularity is the idea to use genes as instrumental variables [i.e., Mendelian randomization (MR)]. However, this approach is problematic because many variables of interest are genetically correlated, which implies the possibility that many genes could affect both the exposure and the outcome directly or via unobserved confounding factors. Thus, pleiotropic effects of genes are themselves a source of bias in nonexperimental data that would also undermine the ability of MR to correct for endogeneity bias from nongenetic sources. Here, we propose an alternative approach, genetic instrumental variable (GIV) regression, that provides estimates for the effect of an exposure on an outcome in the presence of pleiotropy. As a valuable byproduct, GIV regression also provides accurate estimates of the chip heritability of the outcome variable. GIV regression uses polygenic scores (PGSs) for the outcome of interest which can be constructed from genome-wide association study (GWAS) results. By splitting the GWAS sample for the outcome into nonoverlapping subsamples, we obtain multiple indicators of the outcome PGSs that can be used as instruments for each other and, in combination with other methods such as sibling fixed effects, can address endogeneity bias from both pleiotropy and the environment. In two empirical applications, we demonstrate that our approach produces reasonable estimates of the chip heritability of educational attainment (EA) and show that standard regression and MR provide upwardly biased estimates of the effect of body height on EA.

Gender inequality and sexual height dimorphism in Chile.

Chile has experienced significant improvements in its economy; thus, a secular trend in height has been observed in its population. Gender equality has also improved hand in hand with active policies addressing the gender gap in several dimensions (work, education, health) and overall economic improvement. This study examined changes in sexual height dimorphism in four samples of Chilean male and female working-age subjects and attempted to establish associations with gender equality and welfare. Sexual height dimorphism was calculated and compared with gender equality and overall welfare indicators between 1955 and 1995. Sexual height dimorphism reduction was seen to be strongly associated with greater gender equality and some general welfare indicators, such as the infant mortality rate. Gross domestic product per capita was not associated with sexual height dimorphism, but it showed significant associations with gender equality indicators. Overall, the gender gap has been reduced in Chile, which can be observed through improvements in gender equality indicators and a reduction in height dimorphism, mainly in areas associated with women's health. However, gender equality is still far behind in terms of female labour participation and women in political power, which require attention and further improvements.

Body structure, muscular strength and living conditions of primary school children in Warsaw.

The aim of this study was to determine whether the living conditions of school children affects their body structure and muscular strength. Data were taken from 400 girls and 341 boys aged 7-15 years attending nine primary schools in Warsaw in 1997. A questionnaire was completed, anthropological measurements made and two muscular strength tests conducted. The questionnaire asked questions on the children's level of education, their parents' professions and monthly incomes, the number of persons in the family and the number of rooms in the family's apartment/home. Body height, body weight, chest and arm circumferences, grip strength and vertical jump height were measured and used to calculate body mass index, Marty's Index and the Sargent Vertical Jump Index. Statistical tests included Student's t-test, Principal Component Analysis (PCA) and multiple regression analysis. Body height, chest circumference, Sargent Vertical Jump Index and grip strength were significantly greater in the boys than the girls. Two factors, namely 'socioeconomic status' (F1) and 'family size' (F2), describing living conditions, were isolated after PCA. Boys from bigger families (F2) were shorter, with lower weights and BMIs, smaller chest and arm circumferences and greater grip strengths than those from smaller families, whereas girls from families of lower socioeconomic status (F1) weighed less and had greater BMIs and arm circumferences than those from higher socioeconomic status families. The results suggest that boys seem to be more 'ecosensitive' than girls.