Biomechanical aspects of skin aging-the risk of skin breakdown under shear loading increases with age

In skin, the living epidermis is connected to the underlying dermis through a basement membrane, the dermal-epidermal junction (DEJ), which features a three-dimensional interlocking wavy topography. The DEJ flattens with age while there is also an increased probability of skin tears with age. Moreover, in situations where patients with a fragile skin, especially geriatric, malnourished, or incontinent patients, are being moved or are moving in bed or on a chair, clinical evidence indicates that the skin may break down. It is therefore intriguing to question whether the convoluted nature of the DEJ may play an important role in the ability of skin to resist mechanical shear loads. Here, this clinically relevant topic is explored using an idealized, yet sophisticated, parametric multilayer finite element model of the human skin as it ages. The flattening of the DEJ with age was shown to induce significantly higher and more uniformly concentrated normal and shear stresses at the DEJ, which are correlated with higher likelihood of material damage. This study therefore suggests that the risk of skin breakdown under shear loading increases with age.