This paper identifies the health penalty experienced by girls due to having a brother from endogenous sibling gender composition. We propose a girls-to-girls comparison strategy and rule out the confounding effect from the sibship size, birth interval, and birth order. Employing an instrumental variable approach and data from the Chinese Family Panel Studies, we find that girls with a brother are demonstrably shorter and report poorer health. This \"brother\'s penalty\" manifests even prenatally. Alternative explanations, such as birth order disadvantages, are carefully addressed and ruled out. The results hold even after excluding gender-neutral ethnic minorities. This observed penalty is likely attributed to unequal resource allocation within families and potential parental neglect. This penalty is amplified in families with lower income and maternal education, implying resource constraints contribute to gender discrimination. Our findings highlight the importance of addressing intrafamily gender bias for ensuring equal opportunities and health outcomes. Clinical trial registration: Not applicable.

To examine if sibling absence is associated with higher BMI and to identify potential lifestyle factors underlying this effect; to determine if sibling effects on BMI persist into adulthood.
We used data from all five waves of the National Longitudinal Study of Adolescent to Adult Health to study the sibling factors and BMI of 3,563 participants who were in grades 7-12 at first wave (1994-95). These participants were measured again in the second wave (1996), the third wave (2001-2002), the fourth wave (2008-2009), and most recently, the fifth wave (2016-2018). We identified categories of siblings, comparing the BMI of those without siblings either to birth order or sibship size. BMI was calculated based on direct measurements of height and weight; underlying mechanisms were self-reported.
Participants without siblings had significantly higher BMI than those with siblings, across waves, regardless of sibship size. Those without siblings had consistently higher BMI than middle-born, but not last-born participants. Adolescents without siblings reported eating fast food more frequently and spending more screen time.
Sibling absence is associated with higher BMI in adolescence and this difference persists into adulthood.

暂无摘要。

After more than three decades of implementation, China\'s one-child policy has generated a large number of only children. Although extensive research has documented the developmental outcomes of being an only child, research on the parent-child relational quality of the only child is somewhat limited. Using China Education Panel Survey (2014), this study examined whether the only child status was associated with parent-child relationships among Chinese junior high school students. It further explored whether children\'s gender moderated the association between the only child status and parent-child relationships. Two-level ordered logit models suggested that only children were more likely to report a close relationship with their mothers and fathers compared to children from multiple-child families (including two-child families). Taking birth order into consideration, we found that, only children were more likely to have close parent-child relationships than firstborns, whereas no significant differences were found between only children and lastborns. Interaction analyses further suggested that the only child advantages were gender-specific: the positive effects of the only child status were stronger for daughters than for sons, that is, daughters benefited more from being only children. Our findings highlight the importance of considering children\'s gender and birth order in exploring the only child effects in the Chinese context. Additional analyses about sibling-gender composition indicated female children were more likely to be disadvantaged with the presence of younger brothers, whereas male children benefited more from having older sisters. This reveals that the son preference culture is still deep-rooted in the Chinese multiple-child families.

Children with many siblings have lower average educational attainment compared with children raised in smaller families, and this disadvantage by sibship size has been observed across many countries. We still know remarkably little, however, about how sibship size disadvantage has changed within countries and how such trends vary across countries. Using comparative data from 111 surveys from 26 low-fertility countries, we find an overall trend of growing sibship size disadvantage across cohorts in the majority of countries: between the 1931-1940 birth cohort and the 1971-1980 birth cohort, 16 of 26 countries showed a statistically significant increase in sibship size disadvantage in education, while only two countries showed a significant reduction in sibship size disadvantage. The disadvantage in years of education associated with having an additional sibling increased remarkably in post-socialist (0.3) and East Asian countries (0.34) and, to a lesser extent, Western European countries (0.2). In contrast, this disadvantage showed little change in Nordic countries (0.05) and even decreased in Anglo-Saxon countries (-0.11). We discuss explanations and implications of our comparative evidence in the context of the intergenerational transmission of education.

In this article we test the hypothesis that the secular increase in heights in the course of the second half of the nineteenth century was associated with the rise of the breadwinner-homemaker household. In these \'modern\' households, women raised the living standards (quality and quantity of food, hygiene and care) for all members, especially the children. We model the assumed contributions to the family budget by age and gender of household members, and find that a strong imbalance between consumers and producers in the household put severe strains on effective resource allocation, leading to lower net nutrition and lower young adult heights. We suggest a carefully calibrated consumer/producer ratio as an indicator to capture these effects. The ratio is not meant to replace others, and we show that sibling rank order as well as gender preferences also played a role in intra-household resource allocation. For our research, we have used a database with reconstructed life histories (including co-residence) of 3003 Dutch army recruits. Our results indicate that the consumer/producer ratio as experienced by recruits in their early life indeed had a strong impact (-1,8 cm) on their heights. However, this effect differed by social class, which can be explained by differences in acceptance of the income pooling model.

Sibship size and birth order may be contributing factors to the multifactorial etiology of psychosis. Specifically, several studies have shown that sibship size and birth order are associated with schizophrenia. However, there are no studies on their association with psychotic experiences (PE).
Cross-sectional, community-based data from 43 low- and middle-income countries which participated in the World Health Survey were analyzed. The Composite International Diagnostic Interview was used to identify four types of past 12-month PE. The association of sibship size and birth order with PE was assessed with multivariable logistic regression.
The final sample consisted of 212,920 adults [mean (SD) age 38.1 (16.0) years; 50.7% females]. In the multivariable analysis, compared to individuals with no siblings, the OR increased linearly from 1.26 (95%CI = 1.01-1.56) to 1.72 (95%CI = 1.41-2.09) among those with 1 and ≥ 9 siblings, respectively. Compared to the first-born, middle-born individuals were more likely to have PE when having a very high number of siblings (i.e. ≥9).
Future studies should examine the environmental and biological factors underlying the association between sibship size/birth order and PE. Specifically, it may be important to examine the unmeasured factors, such as childhood infections and adversities that may be related to both family structure and PE.

BACKGROUND: Previous studies reported that familial factors such as birth order and mothers atopy might influence cord blood levels and development of allergies.
OBJECTIVE: The aim of the study was to evaluate the relationship of cord blood IgE and maternal IgE with birth order and mothers history of allergy in Albanian mother/neonate pairs.
METHODS: Study population represented 291 mother-infant pairs. Mothers were interviewed with a questionnaire for personal history of allergy and pregnancy history whereas serum IgE levels were determined using sandwich IRMA assay.
RESULTS: The mean level of cIgE in neonates with detectable levels was 1.59 (n = 78). No significant difference in means of cIgE was found between first born and later born neonates (p = 0.232) and between neonates of mothers with a negative and positive history of allergy (p = 0.125). Also, no significant difference was found between means of mIgE by birth order, whereas there was a significant difference of mIgE between mothers with and without a history of allergy (p = 0.01). In a group of neonates with detectable cIgE levels, maternal IgE levels were moderately correlated with cIgE levels.
CONCLUSIONS: Cord blood IgE is not affected by birth order and mothers history of allergy, whereas mothers IgE are affected by the history of allergy but not by birth order.

The Cattell-Horn-Carroll theory is the principal model at present to define and assess intelligence. However, several authors have suggested that the structure of intelligence is not stable throughout life. For example, children tend to present a general ability, which is invested in the development of specific and differentiated abilities during adolescence, reflecting the effect of schooling, experiences, and interests. In this study, an intelligence nine subtests battery was applied to a sample of 470 5-, 7-, and 9-year-old Portuguese children, from public and private basic schools. Two structure models have been tested, one assuming a global general factor loading by the nine subtests, and a second one formed by two factors integrating the verbal and non-verbal subtests. The results provide evidence of better fit of the second model where intelligence performance is organized in traditional verbal and non-verbal factors. This structure model is confirmed taking 5-, 7-, and 9-year-old children subgroups. A posterior path analysis verifies the impact of socio-familial variables in both factors. More than parents\' educational levels and professional status, the results suggest the sibship size appears as more relevant on explanation of children cognitive performance.

Demographic research has paid much attention to the impact of childhood conditions on adult mortality. We focus on one of the key aspects of early life conditions, sibling group size, and examine the causal effect of growing up in a large family on mortality. While previous studies have focused on low- or middle-income countries, we examine whether growing up in a large family is a disadvantage in Sweden, a context where most parents have adequate resources, which are complemented by a generous welfare state. We used Swedish register data and frailty models, examining all-cause and cause-specific mortality between the ages of 40 and 74 for the 1938-72 cohorts, and also a quasi-experimental approach that exploited multiple births as a source of exogenous variation in the number of siblings. Overall our results do not indicate that growing up in a large family has a detrimental effect on longevity in Sweden.