Abstract
Skin ageing is a complex process involving the additive effects of skin's interaction with its external environment, predominantly chronic sun exposure, upon a background of time-dependent intrinsic ageing. Here, using non-invasive cutometry and ballistometry, we explore the consequences of ageing on the biomechanical function of skin in otherwise healthy White Northern European volunteers. Intrinsic skin ageing caused biomechanical decline; skin loses both resilience (P < 0.01) and elasticity (P < 0.001), which is characterised histologically by modest effacement of rete ridges (P < 0.05) and disorganisation of papillary dermal elastic fibres. At photoexposed sites, biomechanical testing identified significant loss of biomechanical function-particularly in the aged cohort. Photoaged forearm displayed severe loss of resilience (P < 0.001) and elasticity (P < 0.001); furthermore with repetitive testing, fatigue (P < 0.001), hysteresis (P < 0.001) and viscous "creep" (P < 0.001) were exacerbated. Histologically, both young and aged forearm displayed flattening of rete ridges and disruption to the arrangement of elastic fibres. We conclude that maintenance of skin architecture is inherently associated with optimal biomechanical properties. Modest perturbations to skin architecture-as exemplified by intrinsic ageing-result in moderate functional decline. Chronic sun exposure causes fundamental changes to the clinical and histological appearance of skin, and these are reflected by an extreme alteration in biomechanical function.