[Analysis of trends and typology of craniofacial features in Central Chinese adults]

Objective: To identify the change trend of craniofacial features in Central China over the past 18 years, identify representative craniofacial features in Central China, and develop an updated typology of craniofacial features. Methods: From May to November 2023, a stratified random sampling method was employed to recruit 3 547 adults from Central China. A total of 4 human body indexes and 19 craniofacial indexes were measured and established a craniofacial characteristic database. Hierarchical clustering algorithms were used to screen representative craniofacial indicators. Weighted generalized linear models were used to recognize the influence factors and change trends for craniofacial indicators. The binary panel was updated based on the bivariate distribution of face width and face length among Central China adults in 2023, while the principal component analysis (PCA) panel was updated based on the 10 craniofacial indicators. Results: Hierarchical clustering analysis identified five categories of craniofacial indexes with one representative craniofacial index in each category, namely, head circumference, bitragion chin arc, lip length, face width, and face length. Weighted generalized linear models showed that age, gender, birthplace, and obesity status were important influential factors. Trend analyses demonstrated that compared with participants during 2005-2007 and 2010-2011, men in 2023 showed larger head circumference, bitragion chin arc, and lip length, but smaller face width, and no statistically significant difference in face length; while women in 2023 showed smaller bitragion chin arc, face length, and face width, and no statistically significant difference in head circumference or lip length. Results from typology study indicated that the existing craniofacial panel was no longer applicable to the current adults in central China. The newly constructed binary panel in central China divided the craniofacial region into 10 cells, with a total coverage of 97.24% (96.26% for males and 98.33% for females) and cell coverages ranging from 4.60% to 17.20%. The newly constructed PCA panel partitioned the craniofacial region into 8 cells, with a total coverage of 96.14% (94.28% for males and 98.21% for females) and cell coverages ranging from 9.42% to 14.91%. Conclusion: Statistically significant changes in craniofacial characteristics were observed among adults in Central China, with age, gender, birthplace, and obesity status identified as key influencing factors. This study updated the binary panel and the PCA panel, which can be applied to the design and fit test of respiratory protection products.