Abstract
BackgroundBirth order has been shown to affect the health of the child; less is known, however, about how birth order affects caries development in children. Thus, the present study investigated the association between birth order and dental caries development in young children.MethodsThis retrospective registry-based cohort study included all children born in 2000–2003 who were residing in Stockholm County, Sweden, at age 3 years (n = 83,147). The study followed the cohort until subjects reached 7 years of age. Children with registry data on dental examinations and sociodemographic characteristics at ages 3- and 7 years constituted the final study cohort (n = 65,259). The outcome variable was “caries increment from age 3- to 7 years” (Δdeft > 0) and the key exposure, “birth order”, was divided into five groups. A forward stepwise logistic binary regression was done for the multivariate analysis with adjustments for sociodemographic factors.ResultsAt age 3 years, 94% had no fillings or manifest caries lesions. During the study period, 22.5% (n = 14,711) developed dental caries. The final logistic regression analysis found a statistically significant positive association between birth order and caries increment. Further, excess risk increased with higher birth order; with the mother’s first-born child as reference, risk for the second-born child was OR 1.17, 95% CI = 1.12–1.23; for the third-born child, OR 1.47, 95% CI = 1.38–1.56; for the fourth-born child, OR 1.69, 95% CI = 1.52–1.88; and for the fifth-born or higher birth-order child, OR 1.84, 95% CI = 1.58–2.14.ConclusionsThese findings show that birth order influences caries development in siblings, suggesting that birth order can be regarded as a predictor for caries development in young children. This factor may be helpful in assessing caries risk in preschool children and should be considered in caries prevention work in young children with older siblings.
Highlights
Birth order has been shown to affect the health of the child; less is known, about how birth order affects caries development in children
The sample calculation was carried out a posteriori, and for the analysis conducted in the present study, it is possible to detect as significant odds ratio higher than 1.2, with 95% confidence interval, and statistical power higher than 80%
Model IV included all groups of potential confounders and found that, compared with the first-born child, second-born children had 1.17 times higher odds of having a caries increment from age 3- to 7 years (1.17 [1.12–1.23]); third-born, 1.47 times higher odds (1.47 [1.38–1.56]); fourth-born, 1.69 times higher odds (1.69 [1.52–1.88]); and fifth-born and higher birth-order children, 1.84 times higher odds (1.84 [1.58–2.14]). The findings of this registry-based longitudinal cohort study revealed that birth order is associated with caries increment in young children between age 3 and 7 years
Summary
Birth order has been shown to affect the health of the child; less is known, about how birth order affects caries development in children. The present study investigated the association between birth order and dental caries development in young children. Previous research has shown that birth order affects health. The differences in health between siblings in a family could be due to many factors, such as parental time and changes in the family environment due to the presence of children of different ages. The first-born child does not share parental time with any siblings, at least not during the first period in life. Since parental time is Julihn et al BMC Public Health (2020) 20:218 finite, succeeding children receive less quality time during their first years [7, 8]
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