Breastfeeding and parents' socioeconomic status buffer dental developmental stress in female infants.

Background and objectives: Linking adult health to early life is limited by a lack of retrospective biomarkers of stress tied to narrow windows of early development. Teeth serve as ideal data sources to examine early life because their hard tissues endure from infancy through adulthood as permanent records of developmental stress. This study examines if dental fluctuating asymmetry (FA) in permanent molars, a measure of instability and plastic responses to stress, is associated with biocultural factors during development. Methodology: Data were sourced from dental casts and health history records of 303 child participants of the longitudinal Burlington Growth Study. Dental FA was calculated from the first and second permanent molar intercuspal distances. Biocultural factors of parental, gestational, and childhood characteristics were grouped into latent dimensions using factor analysis of mixed data, then analyzed against FA using logistic regression separated by sex. Results: Breastfeeding and high and low parental socioeconomic status were associated with lower FA in females. No relationships were found between biocultural factors and FA in males. Conclusion and implications: The sex-specific results are likely due to differences in the nutritional needs of males and females during the first several postnatal months. Furthermore, dimorphism in energetic investment strategies, where males favor body growth while females favor system development, may be responsible for differences in how periods of physiological stress affect biological systems. These results argue for sex-specific investigations of stress biomarkers to better link early life with adult health.