Elsevier

Public Health

Volume 153, December 2017, Pages 44-51
Public Health

Original Research
Increased obesity risks for being an only child in China: findings from a nationally representative study of 19,487 children

https://doi.org/10.1016/j.puhe.2017.07.002Get rights and content

Highlights

  • Only-sons had higher obesity risk than sibling-sons, particularly in urban China.

  • Only-sons spent less time on TV, internet use, after-school sports, and household chores.

  • Only-daughters had high obesity risk than sibling-daughters.

  • Only-daughters in rural areas spent less time on household chores than sibling-daughters.

Abstract

Objectives

Given the rapid demographic transition and obesity growth in China, it is important to study how the large only-child population (≈100 million) might contribute to the obesity epidemic. This study evaluated associations of only-child status with weight and energy expenditure–related behaviors in China and examined how the associations may vary by sex and urbanicity.

Study design

Secondary analyses of nationally representative cross-sectional data from China Education Panel Survey: Junior Cohorts 2013–14, which included 19,487 students from 112 middle schools in 28 regions across China.

Methods

We used propensity-score–weighted multilevel models to test associations between only-child status and weight outcomes.

Results

Compared with sibling-sons, only-sons had higher body mass index (BMI) (Beta = 0.32, P < 0.05) and higher risks of overweight (OR = 1.24, 95% CI = [1.07–1.45]) and obesity (OR = 1.29, 95% CI = [1.02–1.64]); and spent less time on TV watching (Incidence rate ratio (IRR) = 0.89, 95% CI = [0.81–0.98]), internet use (IRR = 0.87, 95% CI = [0.79–0.96]), after-school sports (IRR = 0.91, 95% CI = [0.83–0.99]), and household chores (IRR = 0.85, 95% CI = [0.80–0.92]). Overweight/obesity risks for only-sons were particularly pronounced in urban China, where only-sons were 36% more likely to be overweight and 43% more likely to be obese than sibling-sons. Only-daughters had a higher risk of obesity (OR = 1.43, 95% CI = [1.01–2.04]) than sibling-daughters. However, the association was not significant for either urban girls or rural girls examined separately. Only-daughters in rural areas spent less time helping with household chores (IRR = 0.88, 95% CI = [0.80–0.97]) than sibling-daughters.

Conclusions

Future childhood obesity interventions should pay special attention targeting the large young only-child population in China.

Introduction

As the largest developing country, China has seen a rapid increase in childhood obesity over the past several decades: the combined prevalence of childhood overweight and obesity has increased from 2% in 1981–1985 to 21% in 2006–2010,1 and in some major cities, it has reached above 30% among boys, which is even higher than that in the US.2 Effective interventions are urgently needed.

Family is a critical setting for intervention. Family structure was identified as a key factor affecting children's weight status.3, 4 Studies have consistently reported that being the only child in the family is associated with increased risks of overweight or obesity.5, 6, 7, 8, 9, 10 Only-child status seems to have a dose-response effect: longer duration of being the only child in the family is associated with higher overweight risk.6, 7

Given its large population base, rapid demographic transition, and 30-year one-child policy, China has the largest only-child population in the world (≈100 million).11 Only children in China were often viewed as overweight ‘little emperors’ over-nourished by doting parents and grandparents.12, 13, 14 Accordingly, the one-child policy was often cited as a leading contributor to the rising child obesity epidemic,15 although very few studies have evaluated the obesity risk among only children in China and, among two notable exceptions, null findings were reported.16, 17 Neither study, however, used nationally representative data or considered possible gender and urban-rural variations in the association. Moreover, both studies used conventional regression adjustment in dealing with potential confounding effects, which relies on an untestable assumption about correct model specification. To reduce bias due to potential model misspecification, methods with more robust properties should be used to obtain more precise estimates.

Furthermore, to our knowledge, no study has examined how only-child status may affect energy expenditure–related behaviors among Chinese children. Accordingly, little is known about lifestyle factors that may put only children at increased risks of overweight or obesity.

The present study examined the associations of only-child status with weight status and several energy expenditure–related behaviors based on data from the most recent national data. We also examined how such associations may vary by sex and region. To reduce bias due to confounding and/or potential model misspecification, our estimation followed a combined strategy of propensity score weighting and multilevel regression, which provides a doubly robust estimator yielding consistent estimates if only either the outcome regression model or the propensity score model was correctly specified.18 Findings from this study will inform family-based interventions and projections of future obesity trend in China.

Section snippets

Data and study population

Analyses were done based on data from the baseline wave (2013–2014) of the China Education Panel Survey-Junior High Cohorts (CEPS-JH). Following a stratified multistage sampling design, CEPS-JH is an ongoing panel study of a nationally representative sample of 10,279 seventh grade and 9208 ninth grade students, from 112 schools located in 28 regions across in China. Separate questionnaires were administered to students, parents, teachers, and school principals to collect multilevel information

Characteristics of only- and sibling-children

Overall, 32.9% of all study participants were only children. The percentage of only children significantly varied according to their demographic characteristics (Table 1): it was higher among boys (36.6%, vs 28.7% for girls), urban families (53.6%, vs 21.3% for rural families), the majority ethnic group (36%, vs 15.5% for ethnic minorities), non-migrant families (33.3%, vs 29.2% for migrant families), and families with higher SES (as was indicated by higher parental education, more prestigious

Discussion

Given the rapid demographic transition and obesity growth in China, it is important to study whether the large only-child population might contribute to the obesity epidemic. Based on the first nationally representative data and propensity score weighting method, we found that only child status is a potential risk factor for overweight/obesity, particularly for urban boys. For rural boys, no significant difference in weight status existed between only children and sibling children. For girls,

Ethical approval

The data collection of the China Education Panel Survey-Junior High was approved by the Institutional Review Board at the Renmin University of China. Written informed consent was obtained from study participants.

Funding

The study is funded in part by the US National Institute of Health (NIH, U54 HD070725). The U54 center project is funded by The Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD) and the Office of the Director, National Institutes of Health (OD).

Competing interests

The

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      Given that personality changes somewhat throughout the life span (e.g. Specht, Egloff, & Schmukle, 2011), this does not preclude the possibility that only-children are more self-centered than those with siblings in their youth, but the effect fades with time. Only-children have been found to be different from siblings in many ways, including differences in eyesight (Chu, Khan, Jahn, & Kraemer, 2015), body mass index (Li, Xue, Wang, Wen, & Wang, 2017), depressive symptoms (Jin, Zeng, An, and Xu, 2019), and perceived stress and studying-related life satisfaction (Chu et al., 2015). They have also been found to be higher on character strengths such as humor, curiosity, zest, interpersonal wisdom, and leadership (Guo, Zhang, & Zhang, 2015); the behavioral attribute of self-enhancement (Falbo, 2018); and, when compared to children other than firstborns in general, and lastborns from families of two, achievement motivation (Polit & Falbo, 1987).

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