Mapping the Fine-Scale Aging Landscape of Young Chinese Women: A LOESS-Based Analysis of 45 Biophysical Skin Parameters

Background: Facial skin aging is a complex, progressive process, but subtle and nonlinear changes during young adulthood remain insufficiently characterized. This study aimed to develop an early-aging atlas of facial skin in young Chinese women and to identify key age-related turning points among the various aging traits. Methods: A total of 500 Chinese female volunteers aged 18– 33 years participated in this study. We assessed 45 physiological skin parameters associated with barrier function, color, texture, pigmentation, and wrinkles using various noninvasive skin assessment techniques. Beyond Pearson correlation analysis, we used locally weighted scatterplot smoothing (LOESS) to model how these skin parameters evolve with age, capturing any nonlinear patterns. Results: Age-related facial changes were detectable even within this young cohort. Sebum secretion and skin elasticity declined with age, whereas pigmentation, roughness, and wrinkle-related parameters increased. LOESS analysis suggested several approximate age-related transition points. Around 22 years of age, skin dullness and latent UV damage appeared to increase. Around 25 years, periocular wrinkles and mid-face roughness became more evident. After 27 years, brown spots showed a more apparent upward trend. Around 29– 30 years, skin elasticity showed a more marked decline, accompanied by a secondary decrease in sebum secretion. These LOESS-indicated transition periods should be interpreted as exploratory rather than mathematically confirmed thresholds. Conclusion: Early facial aging in young Chinese women follows asynchronous and nonlinear trajectories across different skin dimensions. The identified transition points before age 30 provide a quantitative basis for understanding the temporal progression of early facial aging and may support age-specific prevention and intervention strategies.