The Association of Birth Order with Later Caries Development in Young Children

Annika Julihn1,2, Annika Julihn1,2, Fernanda Soares Cuhna1, Ulrika Hammarfjord1, Anders Hjern3,4, Göran Dahllöf1,5
1 Division of Orthodontics and Pediatric Dentistry, Department of Dental Medicine, Karolinska Institutet, Huddinge, Stockholm, Sweden
2 Department of Pediatric Dentistry, Eastman Institute, Public Dental Service, Stockholm, Stockholm, Sweden
3 Clinical Epidemiology, Department of Medicine, Karolinska Institutet, Stockholm, Stockholm, Sweden
4 Centre for Health Equity Studies, Stockholm University, Stockholm, Stockholm, Sweden
5 Center for Pediatric Oral Health Research, Public Dental Service, Stockholm, Stockholm, Sweden

Background: Previous data suggesting that children of a high birth order, i.e., with older siblings, are in a disadvantage position and more vulnerable to illness. The aim of this study was therefore to investigate whether birth order is associated with dental caries in young children.

Methods: In this retrospective register-based cohort study, all children born in 2000-2003, and who resided in the county of Stockholm, Sweden, at 3 years of age were included (n=83,147). The cohort was followed until individuals were 7 years of age. During this period, the subjects received regular dental checkups. A total of 65,259 children (33,423 boys and 31,836 girls) were examined at 3 and 7 years of age and thus constituted the final study cohort. Information regarding dental caries was extracted from the Public Health Care Administration in Stockholm. Data concerning perinatal factors as well as parental socio-demographic determinants were extracted from Swedish national registries. To analyze “birth order” as a potential predictor for caries increment (deft>0) in preschool age, we adjusted the variable for potential confounders in multiple logistic regression analyses.

Results: At 3 years of age, 94% had no fillings or caries lesions. During the study period 22.5% (n=14,711) developed dental caries. The final logistic regression analysis showed a significant positive association between birth order and caries increment. Further, with higher birth order the excess risk increased and was for “birth order=2” (OR, 1.24; 95% CI=1.18–1.29), “birth order=3” (OR, 1.63; 95% CI=1.53–1.73), and “birth order=4” (OR, 1.99; 95% CI=1.80–2.21) with mother’s first child as reference. With a birth order of five or more, the excess risk was strongest (OR, 2.15; 95% CI=1.86–2.48).

Conclusions: Birth order can be regarded as a predictor for dental caries and this factor could be helpful for assessing caries risk in preschool children.

Annika Julihn