The Influence of Population Variation and Obesity on Facial Growth

Many studies have indicated that childhood obesity can affect the timing of dental development, accelerating dental maturation (e.g., Hilgers et al., 2006; Mack et al., 2013; Nicholas et al., 2018; Must A et al., 2012). Prior work has also suggested that children with obesity may also experience precocious facial growth and perhaps differences in mandibular dimensions (Vora et al., 2022) especially condylion-pogonion (Ohrn et al., 2002; Sadeghianrizi et al., 2005; Gordon et al. 2021). What remains unclear is whether this difference in timing varies by ancestry group and whether there is an interaction between demographic characteristics and obesity. Variations in facial growth patterns (shape) are also less clear, with studies showing inconsistencies in which aspects of facial shape may be affected (e.g., the contrasting results of Vora et al. 2022 and Gordon et al. 2021). The primary aim of this study was to examine the interaction between demographic characteristics (e.g. ancestry, sex) and environmental factors such as BMI, SES, and food insecurity on the timing and pattern of facial skeletal growth. We hypothesize that (1) children with obesity will show relatively accelerated facial growth regardless of self-reported ancestry; (2) that variation in facial shape related to obesity will be mediated by self-reported ancestry. In this study, we examined facial growth in a sample of contemporary orthodontic patients (n=105) who were prospectively recruited during their “records” (initial) appointment at the UIC Department of Orthodontics. These subjects had lateral cephalograms and height/weight taken during their appointment. They were also given a detailed 12-item demographics questionnaire. The questionnaire consisted of questions regarding self-identified ancestry/ethnicity; ancestry/ethnicity of grandparents; household income; parental educational attainment; and food insecurity. Geometric morphometric analysis of facial shape was carried out. Descriptive statistics and linear regression were used for data analysis. Of the 105 patients recruited, 97 children and adolescents (median age 13.2 years, IQR 11.5-15 years) met the inclusion criteria for this study. No significant association was found between BMI and facial form. However, principal component 3 (PC3, 9.87% of total variation) displayed significance by age (p=0.001), sex (p=0.013), non-Hispanic Asian (p=0.048), and Black self-identified ancestry (p< 0.001) while PC4 (5.36% of total variation) was significant by age (p=0.024). Non-Hispanic Asians had lower PC3 scores, characterized by relatively more obtuse gonial angles, greater chin projection, and less subnasal alveolar prognathism. In contrast, Black subjects were more likely to have higher PC3 scores, characterized by greater subnasal alveolar prognathism and more acute gonial angles. Older subjects had greater nasal bridge protrusion, ramus length, and midfacial protrusion. This study failed to reject our null hypotheses, suggesting no significant differences in the timing or pattern of facial growth between children with and without obesity in our sample. Due to our failure to identify an association between obesity and facial shape in our sample, we were unable to evaluate whether this pattern was mediated by self-reported ancestry (Aim 2). Given the relatively small sample size and contrasting results with prior published work, further research is needed in this area to resolve potential associations between BMI and facial growth. Differences in facial growth patterns may influence orthodontic treatment needs and the optimal timing for orthodontic interventions.