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An exploration of adolescent facial shape changes with age via multilevel partial least squares regression

Farnell, D. J. J. ORCID:, Richmond, S ORCID:, Galloway, J ORCID:, Zhurov, A. I. ORCID:, Pirttiniemi, P, Heikkinen, T, Harila, V, Matthews, H and Claes, P 2021. An exploration of adolescent facial shape changes with age via multilevel partial least squares regression. Computer Methods and Programs in Biomedicine 200 , 105935. 10.1016/j.cmpb.2021.105935

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Background and Objectives Multilevel statistical models represent the existence of hierarchies or clustering within populations of subjects (or shapes in this work). This is a distinct advantage over single-level methods that do not. Multilevel partial-least squares regression (mPLSR) is used here to study facial shape changes with age during adolescence in Welsh and Finnish samples comprising males and females. Methods 3D facial images were obtained for Welsh and Finnish male and female subjects at multiple ages from 12 to 17 years old. 1000 3D points were defined regularly for each shape by using “meshmonk” software. A three-level model was used here, including level 1 (sex/ethnicity); level 2, all “subject” variations excluding sex, ethnicity, and age; and level 3, age. The mathematical formalism of mPLSR is given in an Appendix. Results Differences in facial shape between the ages of 12 and 17 predicted by mPLSR agree well with previous results of multilevel principal components analysis (mPCA); buccal fat is reduced with increasing age and features such as the nose, brow, and chin become larger and more distinct. Differences due to ethnicity and sex are also observed. Plausible simulated faces are predicted from the model for different ages, sexes and ethnicities. Our models provide good representations of the shape data by consideration of appropriate measures of model fit (RMSE and R2). Conclusions Repeat measures in our dataset for the same subject at different ages can only be modelled indirectly at the lowest level of the model at discrete ages via mPCA. By contrast, mPLSR models age explicitly as a continuous covariate, which is a strong advantage of mPLSR over mPCA. These investigations demonstrate that multivariate multilevel methods such as mPLSR can be used to describe such age-related changes for dense 3D point data. mPLSR might be of much use in future for the prediction of facial shapes for missing persons at specific ages or for simulating shapes for syndromes that affect facial shape in new subject populations.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Dentistry
Publisher: Elsevier
ISSN: 0169-2607
Date of First Compliant Deposit: 11 January 2021
Date of Acceptance: 5 January 2021
Last Modified: 04 Jan 2024 17:57

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