Number of siblings, birth order, and childhood overweight: a population-based cross-sectional study in Japan

Abstract

BackgroundAlthough several studies have investigated the relationship between the number of siblings or birth order and childhood overweight, the results are inconsistent. In addition, little is known about the impact of having older or younger siblings on overweight among elementary schoolchildren. The present population-based study investigated the relationship of the number of siblings and birth order with childhood overweight and evaluated the impact of having younger or older siblings on childhood overweight among elementary schoolchildren in Japan.MethodsSubjects comprised fourth-grade schoolchildren (age, 9–10 years) in Ina Town during 1999–2009. Information about subjects’ sex, age, birth weight, birth order, number of siblings, lifestyle, and parents’ age, height, and weight was collected by a self-administered questionnaire, while measurements of subjects’ height and weight were done at school. Childhood overweight was defined according to age- and sex-specific cut-off points proposed by the International Obesity Task Force. A logistic regression model was used to calculate the odds ratio (OR) and 95% confidence intervals (95% CI) of "number of siblings" or "birth order" for overweight.ResultsData from 4026 children were analyzed. Only children (OR: 2.13, 95% CI: 1.45-3.14) and youngest children (1.56, 1.13-2.16) significantly increased ORs for overweight compared with middle children. A larger number of siblings decreased the OR for overweight (P for trend < 0.001). Although there was no statistically significant relationship between a larger number of older siblings and overweight, a larger number of younger siblings resulted in a lower OR for overweight (P for trend < 0.001).ConclusionsBeing an only or youngest child was associated with childhood overweight, and having a larger number of younger siblings was negatively associated with overweight. The present study suggests that public health interventions to prevent childhood overweight need to focus on children from these family backgrounds.

The Effect of Socioeconomic Status, Number of Siblings and Parental of Education on Children’ Body Mass Index at Jeddah, Saudi Arabia: Cross Sectional Study

“…A larger number of siblings decreased the incidence of overweight (P-value<0.001) [25]. Another study done in Los Angeles found children with siblings had lower BMI and were less likely to be obese than children without siblings [26]. A study involving 273 children found the prevalence of an overweight or obese child was 42.5%.…”

Association among number, order and type of siblings and adolescent mental health at age 12

“…Previous research has mainly focused on sibship and disease, and has shown that sibship size has a protective effect against allergies 8 and being overweight. 9,10 Epidemiological studies on the relationship between siblings and mental health have mostly come from Western countries, and few studies exist in Asia. A systematic review showed that sibling conflict was significantly associated with more internalizing and externalizing problems among Caucasian subjects, 3 and the most common type of childhood victimization is peer or sibling assault across cultures.…”

Effect of Sibling Birth on BMI Trajectory in the First 6 Years of Life

“…Our findings are consistent with previous reports from cross-sectional studies that having younger siblings is associated with a lower risk of being overweight and obesity. [3][4][5][6][7][8] To our knowledge, this study is the first to document a longitudinal association between the birth of a sibling and a lesser subsequent increase in BMIz. Although 1 study reported positive child behavior (eg, greater expression of affection and joyful behavior and less aggression) with a birth interval of >2 years between the child and his/her sibling, 13 no previous study has reported a differential effect of the birth of a sibling on child BMIz based on the child's age when his/her sibling was born.…”

“…[3][4][5][6][7][8] However, there is limited understanding of how the birth of a sibling may relate to changes in BMI longitudinally during early childhood. Monitoring changes in child BMI after the birth of a sibling could help further establish the association between having younger siblings and lower child BMI by examining temporality of events.…”