BACKGROUND: Despite persistent concerns about only children\'s disadvantage relative to individuals with siblings, existing health-related evidence is inconsistent. Recent evidence from Nordic countries about only children having poorer health outcomes may not apply elsewhere because selection processes differ across contexts. We investigate the midlife health of only children in the UK where one-child families tend to be socio-economically advantaged relative to large families.
METHODS: Using the 1946, 1958 and 1970 British birth cohort studies, we examine various biomarkers and self-reported measures of chronic disease by sibship size when respondents are aged in their mid-40s, mid-50s and mid-60s. We estimate separate linear probability models for each cohort, age and outcome, adjusting for childhood and early adulthood circumstances.
RESULTS: We found no evidence of only children differing from those with one, two or three or more siblings, at any age, in any of the cohorts, on: heart problems, hypertension, high triglycerides, high glycated haemoglobin or high C-reactive protein. However, compared with only children, the probability for cancer (0.019, 95% confidence interval [CI]: 0.002, 0.035; age 46/1970) and poor general health (0.060, CI: 0.015, 0.127; age 55/1958; and 0.110, CI: 0.052, 0.168; age 63/1946) was higher among those with three or more siblings.
CONCLUSIONS: There is no consistent pattern of only child health disadvantage for midlife chronic disease outcomes across ages or cohorts in the UK. Research should focus on better understanding how sibship size differentials are contingent on context.

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.

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.

We study whether having several siblings decreases the level of educational performance of adolescents and whether this phenomenon can be compensated by other factors such as the economic or cultural resources of the parents. Based on this compensation model, parental resources should be associated with children\'s educational attainments more strongly in families with a higher rather than a lower number of children. We analyzed the Program for International Student Assessment (PISA) data from 20 Western countries and found that better family wealth, an increased level of parental education, and a higher parental occupational status were associated with increased educational attainments more strongly among 15-year-old children who have siblings than among children without siblings. The same effect was not found in the case of family cultural possessions. Although parental resources may matter more in larger families than in smaller families, some types of resources are more important than others regarding compensation.

The aetiology of nasopharyngeal carcinoma (NPC) remains enigmatic in endemic and non-endemic areas. Early-life infection with Epstein-Barr virus (EBV) may predispose to NPC development, whereas delayed primary infection with EBV may cause infectious mononucleosis (IM).
We used Swedish population and health registers to investigate whether potential indicators of early EBV infection, such as birth order, sibship size, maternal age and paternal age, are related to the subsequent risks for NPC and IM. We conducted two nested case-control studies, one for each health outcome, based on 251 NPC case patients, 11 314 IM case patients and five population control subjects per case matched by birth year and sex. We used conditional logistic regression modelling to estimate odds ratios (ORs) and their 95% confidence intervals (CIs) for NPC and IM.
The multivariate-adjusted ORs of developing NPC increased with number of siblings; the ORs associated with having one, two and three or more siblings, compared with none, were 1.59 (95% CI = 0.97, 2.62), 1.94 (95% CI = 1.17, 3.22), and 2.03 (95% CI = 1.23, 3.35), respectively (Ptrend = 0.006). This increased risk of NPC was explained mainly by having older rather than younger siblings. In contrast, lower risks of IM were observed among individuals with an increasing number of older siblings, younger siblings and total siblings.
Early-life social environment, possibly related to EBV infection, contributes to NPC pathogenesis in non-endemic areas. This hypothesis is further supported by the clearly contrasting findings between NPC and IM.