A study of differences in surface roughness between sun-exposed and unexposed skin with age

Background: To understand and separate the roles of age and solar ultraviolet exposure (sun damage) on the surface roughness of skin. Objectives: To determine the effects of age and site (sun exposed vs. unexposed) on skin roughness in normal healthy subjects. Subjects/Methods: Using a stylus profilometer and silicone skin surface replicas, we have measured skin surface roughness parameters on habitually exposed (back of hand) and habitually unexposed (upper buttock) skin sites from the same individual in a sample of 73 subjects from the normal population. We compared the two sites in order to determine any differences in roughness caused, we postulate, by the effect of solar ultraviolet exposure on the exposed site. Results: We found that the two sites are indistinguishable in roughness until after 30 years of age. For the over 30 years group, the difference between exposed and unexposed skin roughness correlated strongly with age. For all ages, skin roughness showed a positive correlation with age on the unexposed, but not the exposed, site. On the hand site subjects aged 40 years and older had significantly smoother skin than those aged less than 40 years, as measured by one roughness parameter. On the back, the older group had significantly rougher skin than the younger group measured by two roughness parameters. Conclusions: We propose that on the back of the hands, solar damage reverses or reduces the increase in roughness which would otherwise be caused by intrinsic ageing.