Age-Associated Thin Hair Displays Molecular, Structural, and Mechanical Characteristic Changes

The study investigates the characteristics of age-associated thin hair in Caucasian women over 50 years old. It finds that thin hairs exhibit significant molecular, structural, and mechanical changes compared to thicker hairs. Specifically, thin hairs show imbalanced expressions of hair keratins and keratin-associated proteins (KAPs), a rounder shape, fewer cuticle layers, and reduced medullae frequency. Mechanically, thin hairs are more rigid, less viscous, and have a lower water diffusion coefficient. These changes suggest that hair thinning with age involves a complex "aged hair program" within the hair follicle, rather than merely producing smaller hairs.