Developmental craniofacial anthropometry: Assessment of race effects

Abstract

Differences in craniofacial anatomy among racial groups have been documented in a variety of structures, but the oral and maxillofacial regions have been shown to be a particularly defining region of variability between different racial/ethnic groups. Such comparisons are informative, but they neither address developmental changes of the craniofacial anatomy nor do they assess or take into account the natural variability within individual races that may account for similar reported, across-group variations. The purpose of this report was to compare-using medical imaging studies-the growth trend of select race-sensitive craniofacial variables in the oral and pharyngeal regions when all races [White, Asian, Black, and Hispanic (AR)] are included versus only a single race category [White (WR)]. Race effect was tested by comparing sex-specific growth fits (fourth degree polynomial model) for AR versus WR data. Findings indicate that the inclusion of all races versus a single race did not significantly alter the growth model fits. Thus, the inclusion of all races permits the advancement of general growth models; however, methodologically, it is best to treat the race variable as a covariate in all future analysis to test for both potential all race effects or individual race effects, on general growth models.

Figure 1

Midsagittal CT image displaying the variables used to assess the anthropometric differences of race for our study. Variables include: Vocal Tract Length (VT Length): the curvilinear line extending from points B to C. Vocal Tract-Vertical (VT-Vertical): vertical distance from points A to J. Nasopharyngeal Length (Nasopharynx): vertical distance from points F to J. Vocal Tract-Horizontal (VT-Horizontal): horizontal distance from points C to G. Oro-hypopharyngeal width (Oropharynx): points F to G.

Figure 2

Growth for the VTL measurement using the fourth degree polynomial regression is shown. The solid line and the dashed line show the model fit for all races (AR) and Whites only (WR) respectively.

Figure 3

Growth for the VT-Vertical measurement using the fourth degree polynomial regression is shown. The solid line and the dashed line show the model fit for all races (AR) and Whites only (WR) respectively

Figure 4

Growth for the VT-Horizontal measurement using the fourth degree polynomial regression is shown. The solid line and the dashed line show the model fit for all races (AR) and Whites only (WR) respectively.

Figure 5

Growth for the each Nasopharynx measurement using the fourth degree polynomial regression is shown. The solid line and the dashed line show the model fit for all races (AR) and Whites only (WR) respectively.

Figure 6

Growth for the Oropharynx measurement using the fourth degree polynomial regression is shown. The solid line and the dashed line show the model fit for all races (AR) and Whites only (WR) respectively.

Figure 7

Stability analysis results for the variables VT-Horizontal and Nasopharynx. The plots display the p-value of the race term in the growth model as a function of the ratio of the number of White subjects to the number of non-White subjects. The ratio range was affected by the number of available age matched White subjects which was more for males than females. The dashed line reflects the level of significance at the 0.05 level.