Assessment of skin barrier function using transepidermal water loss: effect of age

To probe age-related changes in skin barrier function, transepidermal water loss (TEWL) rates have been measured in "young" (19-42 years) and "old" (69-85 years) subjects. TEWL was determined at ventral forearm skin sites, which had been occluded for 24 hr with polypropylene chambers. Baseline TEWL rates (J infinity), which showed no dependence on age, were measured for each subject before and after the experiment. Following removal of the occlusive chamber, TEWL was monitored continuously from t = 0.5 min until its return to the baseline (preocclusion) level, which was typically in the range of 2-7 g/m2/hr. Initial TEWL rates (mean +/- SD) were found to differ significantly between young (28.6 +/- 7.5 g/m2/hr; n = 26) and old (36.9 +/- 10.5 g/m2/hr; n = 18) subjects (P less than 0.01). Relaxation of TEWL to J infinity was significantly slower in the aged cohort, such that the characteristic time for diffusion of water in the stratum corneum was estimated to be (mean +/- SD) 176 +/- 59 min for the young subjects, compared to 360 +/- 76 min for the old (P less than 0.001.). Thus, the initial TEWL value following removal of occlusion is significantly greater, and the excessive stratum corneum hydration produced by occlusion is dissipated more slowly, in old skin than in young. A hypothesis to explain the slower relaxation of perturbed TEWL in old skin is proposed.