title: Characterizing facial skin ageing in humans: disentangling extrinsic from intrinsic biological phenomena.
abstract: Facial skin ageing is caused by intrinsic and extrinsic mechanisms. Intrinsic ageing is highly related to chronological age. Age related skin changes can be measured using clinical and biophysical methods. The aim of this study was to evaluate whether and how clinical characteristics and biophysical parameters are associated with each other with and without adjustment for chronological age. Twenty-four female subjects of three age groups were enrolled. Clinical assessments (global facial skin ageing, wrinkling, and sagging), and biophysical measurements (roughness, colour, skin elasticity, and barrier function) were conducted at both upper cheeks. Pearson's correlations and linear regression models adjusted for age were calculated. Most of the measured parameters were correlated with chronological age (e.g., association with wrinkle score, r = 0.901) and with each other (e.g., residual skin deformation and wrinkle score, r = 0.606). After statistical adjustment for age, only few associations remained (e.g., mean roughness (R z ) and luminance (L (*)),  β = -0.507, R (2) = 0.377). Chronological age as surrogate marker for intrinsic ageing has the most important influence on most facial skin ageing signs. Changes in skin elasticity, wrinkling, sagging, and yellowness seem to be caused by additional extrinsic ageing.
authors.affiliation: Clinical Research Center for Hair and Skin Science, Department of Dermatology and Allergy, Charité-Universitätsmedizin Berlin, Charitéplatz 1, 10117 Berlin, Germany.
authors.forename: Carina
authors.initials: C
authors.lastname: Trojahn
authors.affiliation: Clinical Research Center for Hair and Skin Science, Department of Dermatology and Allergy, Charité-Universitätsmedizin Berlin, Charitéplatz 1, 10117 Berlin, Germany.
authors.forename: Gabor
authors.initials: G
authors.lastname: Dobos
authors.affiliation: Clinical Research Center for Hair and Skin Science, Department of Dermatology and Allergy, Charité-Universitätsmedizin Berlin, Charitéplatz 1, 10117 Berlin, Germany.
authors.forename: Andrea
authors.initials: A
authors.lastname: Lichterfeld
authors.affiliation: Clinical Research Center for Hair and Skin Science, Department of Dermatology and Allergy, Charité-Universitätsmedizin Berlin, Charitéplatz 1, 10117 Berlin, Germany.
authors.forename: Ulrike
authors.initials: U
authors.lastname: Blume-Peytavi
authors.affiliation: Clinical Research Center for Hair and Skin Science, Department of Dermatology and Allergy, Charité-Universitätsmedizin Berlin, Charitéplatz 1, 10117 Berlin, Germany.
authors.forename: Jan
authors.initials: J
authors.lastname: Kottner
mesh_terms: D000328:Adult; D000368:Aged; D000375:Aging / Q000473:pathology*; D001686:Biological Phenomena; D002610:Cheek / Q000473:pathology; D005145:Face / Q000473:pathology*; D005260:Female; D006801:Humans; D008875:Middle Aged; D012867:Skin / Q000473:pathology*; D015595:Skin Aging / Q000473:pathology*