Noninvasive measurement of the effect of lifetime exposure to the sun on the aged skin.

The cumulative and comparative effects of chronological and actinic changes to the skin were studied in an elderly population. Two adjacent sites with different degrees of exposure to the sun were examined to distinguish the contribution of each factor, by means of noninvasive measurements. The following parameters were measured on the skin of the low neck (an exposed site), as well as on the adjacent clothes-protected skin of 30 elderly women: electrical conductance, color, microrelief, biomechanical properties and the thickness of both the full skin and the subepidermal nonechogenic band (SENEB), using ultrasound measurements. Persistent exposure to the sun accentuated most of the age-induced modifications. The following changes were significantly more marked in exposed skin: SENEB thickening, full-skin thinning, loss of extensibility and elasticity, and color heterogeneity. The cumulative effects of sun exposure and chronological aging lead to atrophy in elderly people. These results suggest that, if there is an autoprotective skin reaction, such as thickening in young adults, it is eliminated in old people.