Being an Only or Last-Born Child Increases Later Risk of Obesity

University of Cincinnati, United States of America
PLoS ONE (Impact Factor: 3.23). 02/2013; 8(2):e56357. DOI: 10.1371/journal.pone.0056357
Source: PubMed


Studies have suggested that number of siblings and birth order is associated with obesity. However, studies combining these exposures are needed. This study aimed at investigating obesity in children and young adults in regard to different combinations of family size and birth order.
TWO COHORTS SELECTED FROM THE GENERAL POPULATION WERE INVESTIGATED: The Copenhagen School Health Records Register (CSHRR) and a Draft Board (DB) sample with measured heights and weights in childhood (age 13 years) and young adulthood (age 19 years), respectively. Information on birth order, number of siblings, and relevant covariates were available on 29 327 children, as well as on 323 obese young men and 575 randomly selected controls of young men representing approximately 58 000. The relation between number of siblings and birth order, respectively, and having a Body Mass Index (BMI) z-score above or equal to the 95(th) percentile in childhood or having a BMI of at least 31.00 kg/m(2) in young adulthood was analysed using logistic regression analyses adjusted for relevant confounders.
Only children had significantly higher odds of obesity both in childhood and in young adulthood compared with children with siblings, odds ratio (OR) = 1.44 (95% Confidence Interval (CI): 1.26-1.66) and OR = 1.76 (95% CI: 1.18-2.61), respectively. No association between first-born status and obesity was found. The OR of last-born children being obese was also significantly increased in childhood, e.g. OR = 1.93 (95% CI: 1.09-3.43) of obesity if last-born in a family of four children. This was not found in young adulthood. Additionally, higher spacing to previous sibling (average 1872 vs. 1303 days; p = 0.026 in four children families) was observed in obese last-born compared to non-obese last-born children.
Being an only or last-born child is associated with obesity. These associations may provide leads to targeted prevention of obesity in children.

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Available from: Teresa Adeltoft Ajslev, Apr 02, 2014
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    • "The underlying process for increased obesity risk of only children and youngest siblings is not well established (Chen & Escarce, 2010; Haugaard et al., 2013; Hunsberger et al., 2012). This is primarily due to the use of less comprehensive behavioral measures in previous studies and/or less discrete categorization of birth order (i.e., combining only children and oldest siblings in the same comparison group) (Chen & Escarce, 2010; Drucker, Hammer, Agras, & Bryson, 1999; Duke, Bryson, Hammer, & Agras, 2004; Haugaard et al., 2013; Hesketh et al., 2007; Hunsberger et al., 2012; Ochiai et al., 2012). Evidence from social science research suggests that children within the same family can experience a non-shared home environment and dissimilar parenting behavior (Dunn & Plomin, 1991; Hotz & Pantano, 2013; Kidwell, 1981). "
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    ABSTRACT: Birth order has been associated with childhood obesity. The objective of this cross-sectional study was to examine maternal feeding and child eating behaviors as underlying processes for increased weight status of only children and youngest siblings. Participants included 274 low-income 4-8 year old children and their mothers. The dyads completed a videotaped laboratory mealtime observation. Mothers completed the Caregiver's Feeding Styles Questionnaire and the Children's Eating Behavior Questionnaire. Child weight and height were measured using standardized procedures. Path analysis was used to examine associations of birth order, maternal feeding behaviors, child eating behavior, and child overweight/obese status. The association between only child status and greater likelihood of overweight/obesity was fully mediated by higher maternal Verbal Discouragement to eat and lower maternal Praise (all p values < 0.05). The association between youngest sibling status and greater likelihood of overweight/obesity was partially mediated by lower maternal Praise and lower child Food Fussiness (all p values < 0.05). Results provide support for our hypothesis that maternal control and support and child food acceptance are underlying pathways for the association between birth order and weight status. Future findings can help inform family-based programs by guiding family counseling and tailoring of recommendations for family mealtime interactions. Copyright © 2015. Published by Elsevier Ltd.
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    ABSTRACT: Birth order has been suggested to be linked to several cardiovascular disease (CVD) risk factors, but the evidence is still inconsistent. We aim to determine the associations of birth order with body mass index (BMI), muscle strength and blood pressure. Further we will analyse whether these relationships are affected by family characteristics. BMI, elbow flexion, hand grip and knee extension strength and systolic and diastolic blood pressure were measured at conscription examination in 1 065 710 Swedish young men born between 1951 and 1975. The data were analysed using linear multivariate and fixed effects regression models; the latter compare siblings and account for genetic and social factors shared by brothers. FIXED EFFECT REGRESSION ANALYSIS SHOWED THAT BIRTH ORDER WAS INVERSELY ASSOCIATED WITH BMI: second and third born had 0.8% and 1.1% (p<0.001) lower BMI than first-born, respectively. The association pattern differed among muscle strengths. After adjustment for BMI, first-born presented lower elbow flexion and hand grip strength than second-born (-5.9 N and -3.8 N, respectively, p<0.001). Knee extension strength was inversely related to birth order though not always significantly. The association between birth order and blood pressure was not significant. Birth order is negatively associated with BMI and knee extension strength, positively with elbow flexion and hand grip strength, and is not associated with blood pressure among young men. Although the effects are small, the link between birth order and some CVD risk factors is already detectable in young adulthood.
    Full-text · Article · May 2013 · PLoS ONE
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    ABSTRACT: Background: Previous studies have found greater adiposity and cardiovascular risk in first born children. The causality of this association is not clear. Examining the association in diverse populations may lead to improved insight. Methods: We examine the association between birth order and body mass index (BMI), systolic and diastolic blood pressure (SBP/DBP) in the 2004 Pelotas cohort from southern Brazil and the Avon Longitudinal Study of Parents and Children (ALSPAC) from Bristol, south-west England, restricting analysis to families with two children in order to remove confounding by family size. Results: No consistent differences in BMI, SBP or DBP were observed comparing first and second born children. Within the Pelotas 2004 cohort, first born females were thinner, with lower SBP and DBP; for example, mean difference in SBP comparing first with second born was −0.979 (95% confidence interval −2.901 to 0.943). In ALSPAC, first born females had higher BMI, SBP and DBP. In both cohorts, associations tended to be in the opposite direction in males, although no statistical evidence for gender interactions was found. Conclusions: The findings do not support an association between birth order and BMI or blood pressure. Differences to previous studies may be explained by differences in populations and/or confounding by family size in previous studies.
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