Using noninvasive measurement techniques, parameters representing skin characteristics were measured in a total of 117 Japanese females ranging in age from 3 to 65 years. The parameters measured were sebum secretion rate, transepidermal water loss, skin surface conductance, skin color, skin surface temperature, corneocyte surface area, and skin surface microtopography. Measurements were taken twice for each subject, once in the summer (July) and again in the winter (December). Polynomial regression analysis was used to quantitatively assess age-related trends associated with changes in shin parameters. Also, to evaluate the progression of the aging phenomena in adults (i.e., physiological aging), multiple regression analysis was carried out with age as the criterion variable and the above parameters as predictor variables.
The results of these analyses established the following facts: Most physiological skin parameters undergo changes that can be characterized by curves which attain peak values during the third decade of life, whereas morphological parameters tend to vary linearly with age. Until the third dacade of life, the physiological functions of female skin remain in the developmental phase and are extremely prone to fluctuations. However, during the third decade, the physiological development of the skin reaches a stage of completion and becomes comparatively stable, and thereafter commences a gradual transition to senescence concomitant with chronological aging. The degree of skin aging can be estimated by a quantiative assessment of age-related physiological phenomena and a comprehensive analysis of the relevant data.
