GWAS OF SKIN AGING IN KOREAN POPULATION 65 various populations are actively being conducted, and data on new genetic variations and characteristics by race have been reported (22–24). However, the available skin GWAS results are largely limited to the traits of skin pigmentation, sensitivity to the sun, and infl ammation. Although GWASs of pigmentation and sensitivity have been published, no such studies exist regarding the Korean population. The aim of this study was to identify the indicators of skin changes based on genetic variants specifi c to Koreans and to provide personalized solutions based on these indicators. MATERIALS A ND METHODS PARTICIPANT S The sample population investigated in this study consisted of 1,079 Korean women recruited between January 2019 and November 2019 at P&K Skin Research Center (Seoul, Korea). All recruited participants were female without skin-related diseases, and their average age was 40.81 years (Table I). All participants provided written informed consent, and this study was approved by the Institutional Review Board of the Theragen Etex Bio Institute (IRB No.: 700062-20190819-GP-006-01). MEASUREMENT OF SKIN PHENOTYPES To measure skin traits, various measuring devices were used. For wrinkles, a Primos CR (Canfi eld Scientifi c, Parsippany, NJ) was used to perform measurements at wrinkle sites, including the average roughness on the side of the eye, the maximum wrinkle depth on the side of the eye, the average roughness of the glabella, and the maximum wrinkle depth of the glabella. A CM-825 Corneometer® (EnviroDerm Services Ltd., Hedworth, Grange Court, United Kingdom.) was used to measure moisture content of the glabella and cheek. Pigmentation was divided into melanin and brightness categories using a Mexameter® MX 18 (Courage + Khazaka electronic GmbH, Köln, Germany) and a CM-700d (Konica Minolta inc., Tokyo, Japan) instrument, respectively. To identify the skin oil content, the average oil content was measured using an SM 815 Sebumeter® (Courage + Khazaka elec- tronic GmbH., Köln, Germany) on the glabella and right cheek. Finally, we performed a sensitivity assay in which a 10% lactic acid treatment was applied to the skin over time no measuring device was used for this assay because skin sensitivity is specifi c to the individual, and individual sensitivity was identifi ed on the basis of the skin’s reaction. TARGET SKIN PHEN OTYPE GRADING SCALE It can be compli cated to use measured values to perform GWASs because the measured values for the same phenotype may differ according to the measurement instrument. To solve this problem, we scored each measurement item using codes. The measured values for each item were divided into tertile criteria to delineate groups, and scoring was performed for each tertile group to quantify the integrated score for the target phenotype (Table II). Therefore, we sum- marized the total score for the “target phenotype for GWAS” and analyzed each phenotype.

Table I Baseline Characteristic and Skin Measurement Information of the Subjects of This Study Characteristic Average ± SD or N (%) Population () 1,079 Gender (female, %) 100% Age (years, mean ± SD) 40.81 ± 10.90 Phenotype (equipment) Measure item Code Average ± SD or N (%) Wrinkle (Primos CR) Eye (right) Average roughness (Ra) W101 20.81 ± 5.24 Maximum depth (Rmax) W102 198.47 ± 71.97 Glabella Average roughness (Ra) W103 25.18 ± 7.06 Maximum depth (Rmax) W104 193.75 ± 69.61 Moisture (Corneometer) Glabella Moisture content (A.U.) A101 64.84 ± 9.97 Cheek (right) Moisture content (A.U.) A102 70.13 ± 9.48 Melanin (Mexameter) Pigmentation site Melanin (M.I.) M101 166.15 ± 35.83 Nonpigmentation site Melanin (M.I.) M102 119.25 ± 28.35 Brightness (CM-700d) Pigmentation site Brightness (L*) R201 59.95 ± 2.62 Nonpigmentation site Brightness (L*) R202 63.22 ± 2.33 Oil (Sebumeter) Glabella Oil content (g/cm)2 μ L101 85.19 ± 61.23 Cheek (right) Oil content (g/cm)2 μ L102 48.57 ± 42.49 Sensitivity (10% lactic acid) Sensitive S101 534 (49.5%) Nonsensitive S101 545 (50.5%) JOURNAL OF COSMETIC SCIENCE 66