Skin aging and photoaging: an overview.

As the population ages, common skin disorders of the elderly demand greater attention. Moreover, the many clinical, histologic, and physiologic changes that characterize old skin are increasingly implicated in its vulnerability to environmental injury and certain diseases. Thus it behooves dermatologists to study the basic biologic process of aging in the skin and the separable process of photoaging, which itself is a major clinical problem. To date studies at the cellular level have demonstrated major functional losses, particularly in proliferative capacity between infancy and adulthood, with definite further loss between early and late adulthood and as a result of chronic sun exposure. Continued careful, quantitative assessment of aging and photoaging in human skin both in vivo and in vitro will be critical to a better understanding of these processes and particularly to their successful therapeutic modification.