Leveque J L, Corcuff P, de Rigal J, Agache P
Int J Dermatol. 1984 Jun;23(5):322-9. doi: 10.1111/j.1365-4362.1984.tb04061.x.
In vivo measurements taken by valid methods, help to interpret the phenomena associated with the aging process. The authors developed some routine techniques to measure physical properties of the skin both deep in the dermis-epidermis and at the surface (stratum corneum). Measurements on the forearm of 150 people yielded the following results regarding the dermis-epidermis level: (1) skin thickness begins to decrease at 45 years of age for men and women, when women's skin becomes thinner than men's skin; (2) torsion extensibility, normalized for a given skin thickness, sharply decreases after 35 years of age; (3) skin optical properties are modified, ie the photoplethysmographic signal, measured on the forehead, greatly increase after 60 years of age; (4) at the cutaneous surface level, the main modifications are increased shedding of stratum corneum after 60 years of age in parallel with a modification of the stratum corneum cohesivity, altered skin microrelief during the aging process, and slightly decreased transepidermal water loss while the corneocyte projected size increases. These findings allow consideration of the aging process at the skin level as a phased process. The alterations of the physical properties and their kinetics suggest a various process according to the different cutaneous sections.
采用有效方法进行的体内测量有助于解释与衰老过程相关的现象。作者开发了一些常规技术来测量真皮 - 表皮深层以及皮肤表面（角质层）的皮肤物理特性。对150人的前臂进行测量后，得出了以下关于真皮 - 表皮层的结果：（1）男性和女性在45岁时皮肤厚度开始下降，此时女性的皮肤比男性的皮肤更薄；（2）在给定皮肤厚度下归一化的扭转伸展性在35岁后急剧下降；（3）皮肤光学特性发生改变，即在前额测量的光电容积脉搏波信号在60岁后大幅增加；（4）在皮肤表面水平，主要变化包括60岁后角质层脱落增加，同时角质层内聚力发生改变，衰老过程中皮肤微观起伏改变，经表皮水分流失略有减少，而角质形成细胞突出尺寸增加。这些发现使得可以将皮肤层面的衰老过程视为一个分阶段的过程。物理特性及其动力学的改变表明，根据不同的皮肤部位，存在不同的过程。
