Functional decline in facial expression generation in older women: A cross-sectional study using three-dimensional morphometry

RESEARCH ARTICLE Functional decline in facial expression generation in older women: A cross-sectional study using three-dimensional morphometry Chihiro Tanikawa1,2, Sadaki Takata3, Ruriko Takano4, Haruna Yamanami5, Zere Edlira ID1, Kenji Takada ID2,6* a1111111111 a1111111111 a1111111111 a1111111111 a1111111111 1 Department of Orthodontics and Dentofacial Orthopedics, Graduate School of Dentistry, Osaka University, Suita, Osaka, Japan, 2 Center for Advanced Medical Engineering and Informatics, Osaka University, Suita, Osaka, Japan, 3 Department of Fashion & Beauty Sciences, Osaka Shoin Women’s University, HigashiOsaka, Osaka, Japan, 4 Corporate Culture Department, Shiseido Co., ltd., Tokyo, Japan, 5 Shiseido Global Innovation Center, Shiseido Co., ltd., Yokohama, Kanagawa, Japan, 6 Faculty of Dentistry, National University of Singapore, Singapore, Republic of Singapore * Abstract OPEN ACCESS Citation: Tanikawa C, Takata S, Takano R, Yamanami H, Edlira Z, Takada K (2019) Functional decline in facial expression generation in older women: A cross-sectional study using threedimensional morphometry. PLoS ONE 14(7): e0219451. https://doi.org/10.1371/journal. pone.0219451 Editor: Zhenan Sun, Institute of Automation, Chinese Academy of Sciences (CASIA), CHINA Received: November 2, 2018 Accepted: June 24, 2019 Published: July 10, 2019 Copyright: © 2019 Tanikawa et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Data Availability Statement: All relevant data are now available from the Dryad database, under the DOI: https://doi.org/10.5061/dryad.vh17k68. Funding: This work was partially supported by Shiseido Co., ltd., JSPS KAKENHI (grant no. 22792048 and 25862008), and JST COI (grant no. R1WD07). The funder (Shiseido Co., ltd.) provided support in the form of salaries for authors [ST, RT, HY], but did not have any additional role in the study design, data collection and analysis, decision Elderly people show a decline in the ability to decode facial expressions, but also experience age-related facial structure changes that may render their facial expressions harder to decode. However, to date there is no empirical evidence to support the latter mechanism. The objective of this study was to assess the effects of age on facial morphology at rest and during smiling, in younger (n = 100; age range, 18–32 years) and older (n = 30; age range, 55–65 years) Japanese women. Three-dimensional images of each subject’s face at rest and during smiling were obtained and wire mesh fitting was performed on each image to quantify the facial surface morphology. The mean node coordinates in each facial posture were compared between the groups using t-tests. Further, the node coordinates of the fitted mesh were entered into a principal component analysis (PCA) and a multifactor analysis of variance (MANOVA) to examine the direct interactions of aging and facial postures on the 3D facial morphology. The results indicated that there were significant age-related 3D facial changes in facial expression generation and the transition from resting to smiling produced a smaller amount of soft tissue movement in the older group than in the younger group. Further, 185 surface configuration variables were extracted and the variables were used to create four discriminant functions: the age-group discrimination for each facial expression, and the facial expression discrimination for each age group. For facial expression discrimination, the older group showed 80% accuracy with 2 of 66 significant variables, whereas the younger group showed 99% accuracy with 15 of 144 significant variables. These results indicate that in both facial expressions, the facial morphology was distinctly different in the younger and older subjects, and that in the older group, the facial morphology during smiling could not be as easily discriminated from the morphology at rest as in the younger group. These results may help to explain one aspect of the communication dysfunction observed in older people. PLOS ONE | https://doi.org/10.1371/journal.pone.0219451 July 10, 2019 1 / 21 Facial expression and aging to publish, or preparation of the manuscript. The specific roles of these authors are articulated in the ‘author contributions’ section. Competing interests: The authors declare the following interest: "This work was partially supported by Shiseido Co., ltd. ST, RT, and HY are employed by Shiseido Co., ltd. Further, the funder (Shiseido Co., ltd.) and Osaka University have submitted a patent application based on the results of the present study (Device, method, program, and system for determining three-dimensional facial form, PCT/JP2019/012719). This does not alter our adherence to PLoS ONE policies on sharing data and materials. Introduction Facial expressions play an important role in the communication of emotions and thoughts. It is no exaggeration to say that the face is an organ of communication. Aging is related to impairment of various motor and cognitive functions. A recent study that examined the perception of emotions found that facial expressions have reduced signal clarity when shown on older faces, especially for smiling [1]. This suggests that aging results in dysfunctional communication. However, the mechanisms underlying age-related communication dysfunction are incompletely understood. Aging of the face affects facial configurations and their changes during facial expressions. A Moire 3D analysis system determined that facial sagging becomes progressively more noticeable with aging [2]. Three-dimensional analysis of labial morphology showed a significant effect of age on labial thickness and area [3]. A study comparing 3D faces of mothers and daughters found that the greatest atrophy associated with aging was observed in the upper lip, lateral canthi, labial commissures, and gonial angle [4]. When optical images were used to distinguish nasolabial lines, it was found that the lines were significantly increased age-dependently [5]. A study that investigated age effects on the relationship between teeth and facial soft tissue found that the perioral soft tissues dropped down in older subjects and the soft tissue descended along the entire labial arch [6]. Another study found that young people had a larger lip area and thickness than elderly people [3] [7]. A recent study showed that facial features at rest are more reliable aging biomarkers than blood profiles [8], in which eye slopes were identified as highly associated with age. These results show that aging affects the facial configuration at rest; however, there remain unanswered questions about the effects of aging on facial configurations during smiling. In the present study, we focused on female subjects, because the functional decline in facial expression recog (...truncated)