A reflectometric study of the skin in Dutch families

Abstract

In the period February–May 1968 the reflectances of the exposed (forehead) and unexposed (inside upper arm) skin, were measured at nine wavelengths (430, 470, 490, 520, 550, 580, 600, 660 and 685 mμ), using an “EEL” Reflectance Spectrophotometer in 100 Dutch families. The reflectance curves of upper arm and forehead show the shape usually found in white persons. The skin colour of the upper arm is lighter than that of the forehead in males and females. A difference in skin colour between males and females is observed. The forehead reflectances of males are lower than of females, and the upper arm reflectances of females are lower than those of males. A similarly directed sex difference in skin colour at the forehead has been found in other white groups. If no difference in reaction on exposure exists between both sexes, then the skin colour of the male upper arm will be lighter than that of females, although males in general are more exposed to radiation, because male arms are less uncovered than female arms. No change in skin colour at the upper arm is observed during ageing. As judged from the wavelengths concerned the changes in skin colour at the forehead during ageing result for the greater part both from a regular accumulation of melanin, and an increase in the blood flow of the skin, particularly during the years 11–25. Intrafamilial reflectance resemblances are investigated by means of correlations computed from the upper arm reflectance values measured at wavelengths 550 and 685 mμ. Significant positive correlations between the parents, 0·299 (wavelength 550 mμ) and 0·226 (wavelength 685 mμ) respectively, indicate positive assortative mating. The pattern of intrafamilial correlation coefficients suggests a role of X-chromosomal genes in the causation of the variability in the reflectances measured at wavelength 685 mμ (a measure of melanin deposition). Intrafamilial correlation computations of reflectances measured at wavelength 550 mμ (a measure of vascular response) show some positive correlations, but the role of genes in the causation of the variability in these reflectances remains unclear.