Cephalofacial Morphology of Tibetan Young Adults: Direct Anthropometric Norms and Variations by Sex, Age, Region, and BMI

BACKGROUND: The distinct morphology of the Tibetan population, shaped by high-altitude adaptation, lacks comprehensive anthropometric norms derived from direct measurement. Existing studies have largely relied on photogrammetry, limiting precision for surgical and forensic applications. This study aimed to establish robust cephalofacial anthropometric norms for Tibetan young adults and quantify the influence of sex, age, geography, and body composition. MATERIALS AND METHODS: This cross-sectional study included 508 healthy Tibetan young adults (233 men, 275 women; mean age 20.35±1.67 years) from 4 prefectures in Tibet. Direct anthropometry captured 6 linear dimensions: auricular head height (AH), morphologic facial height (MFH), maximum head breadth (HB), minimum frontal breadth (FB), bizygomatic breadth (BIZ), and bigonial breadth (BIG); alongside 5 indices: vertical cephalofacial index (VCFI), transverse cephalofacial index (TCFI), transverse frontoparietal index (TFPI), zygomatic mandibular index (ZMI), and zygomatic frontal index (ZFI). Group differences were analyzed using Mann-Whitney U and Kruskal-Wallis tests; determinants were identified by multiple linear regression. RESULTS: Significant sexual dimorphism existed; men had larger HB (Z=-12.82, P<0.01) and BIG (Z=-6.62, P<0.01), while women had a higher VCFI (102.29±26.71 vs. 91.56±7.42, P<0.01). Regional variations were distinct; Chamdo men exhibited wider BIZ than Shigatse men (mean difference=0.57 cm, Cohen's d=0.81). Age-related differences showed that men aged 23-25 years had larger FB than the 18-20 group (mean difference=0.43 cm, d=0.68), and women aged 21 to 22 had higher VCFI than the 18 to 20 group (mean difference=11.48, d=0.45). BMI positively correlated with BIZ (men: r=0.352, P<0.01; women: r=0.331, P<0.01) and TCFI (men: r=0.157, P=0.016; women: r=0.199, P<0.01). Multiple linear regression confirmed BMI as a dominant predictor for BIZ (men: β=0.384, P<0.01; women: β=0.325, P<0.01), and age as an independent predictor for male FB (B=0.055, P<0.05). CONCLUSION: This study establishes a comprehensive direct anthropometric dataset for Tibetan young adults. The findings quantify distinct sexual dimorphism, significant regional diversity, BMI-related morphologic variation, and potential prolonged transverse growth in men. These population-specific norms offer a vital quantitative reference for optimizing craniomaxillofacial surgery and forensic profiling for high-altitude populations.