Structural Characteristics of Facial Sagging: A Quantitative Analysis Linking Visual Assessment to Dermal, Fat, and Muscle Properties

BACKGROUND: Facial sagging is associated with changes in underlying facial structures, including the dermis, subcutaneous fat, and muscle layers. However, previous studies have focused primarily on surface appearance, and quantitative evaluations linking sagging to individual internal structures remain limited, making it difficult to identify key determinants of sagging and to optimize intervention targets. OBJECTIVE: This study aimed to clarify, using statistical analyses and predictive models, the contributions of quantitative structural parameters of the dermis, subcutaneous fat, and muscle to facial sagging, and to obtain fundamental insights for individualized evaluation and intervention optimization. METHODS: A total of 220 women aged 20-79 years were enrolled. Facial sagging was assessed using the Merz Scale. Dermal properties were quantitatively measured. The thickness and echogenicity of subcutaneous fat and muscle layers were evaluated using high-resolution ultrasound. Skin displacement and volume increase associated with postural changes were calculated as dynamic sagging indices. Associations between structural characteristics and sagging indices were analyzed using correlation and multiple regression analyses. RESULTS: Sagging appearance was significantly correlated with dermal viscoelasticity, subcutaneous fat thickness, and zygomaticus major muscle thickness. Regression analysis indicated that sagging was jointly influenced by dermal, fat, and muscle characteristics, with relative structural contributions varying by facial site and age. Dynamic sagging indices were significantly correlated with age and Merz scores. CONCLUSION: This study demonstrated that facial sagging is not attributable to aging of a single layer but results from overlapping changes in the dermis, subcutaneous fat, and muscle layers, highlighting the necessity of integrated structural evaluation. TRIAL REGISTRATION: UMIN Clinical Trials Registry: UMIN000060199.