Abstract

We investigate age-related changes of the dermal reduced scattering coefficient in human skin using a recently introduced methodology for non-invasive characterization of structure and composition of skin in vivo. The approach combines pulsed photothermal radiometry (PPTR) with diffuse reflectance spectroscopy (DRS) in visible part of the spectrum. The experimental data are fitted simultaneously with the respective predictions of a dedicated numerical model of light and heat transport in healthy skin (i.e., inverse Monte Carlo). For this purpose, we apply a four-layer optical skin model consisting of epidermis, upper dermis, lower dermis, and subcutaneous adipose tissue.

The study is based on 24 measurements of test sites on the ventral side of the forearm in 9 women and 9 men with healthy fair skin, between 20 and 65 years old. Linear regression analysis of the assessed dermal reduced scattering coefficient values at 500 nm (a_der) indicated no significant variation with the person’s age. Meanwhile, strong correlations of a_der with the blood contents in both papillary and reticular dermis were observed. Separating the respective contributions of these three variables using multiple linear regression (MLR) analysis revealed a highly significant influence of person’s age on a_der (with Pearson’s correlation coefficient r = -0.55 and p < 0.0001). Specifically, by excluding the direct influence of the dermal blood contents, a_der decreases with age by approximately 0.2 mm^-1 per decade. In addition, the values obtained for older persons are in good agreement with the results from a large cohort study performed by Jonasson et al. (J. Biomed. Opt. 2018).

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