Population-based characterisation of child and adolescent oral microbiomes

The factors influencing the oral microbiome during childhood and adolescence remain under-explored at the population level. We characterised the saliva microbiomes of 4,812 children aged 5-18 years within the Spit for Science cohort collected at the Ontario Science Centre (Toronto, Canada), making this the largest population cohort of the paediatric oral microbiome to date. Exploration of participant genotyping and more than 50 variables encompassing the demographics, health, diet, socioeconomic status and living environment of participants revealed that almost all of the investigated variables were associated with overall community structure and/or the abundance of specific bacterial genera. However, most of these associations were modest, while the strongest determinants of oral microbiome composition were shared household environment, age, and ethnicity. We further show that the oral microbiome is more consistent with more core taxa among children than adults, and that microbial differences attributed to ethnicity and diet are likely intertwined. These findings highlight the complex interplay between social, environmental, and biological factors in shaping the developing oral microbiome. This underscores the importance of inclusive, demographically diverse cohorts in microbiome research and presents a reference for the variables that are important to account for in paediatric oral microbiome studies.