Supplementary Material for: The Singapore/Malaysia Cross-sectional Genetics Epidemiology Study: An Updated and Detailed Analysis of Acne Vulgaris Severity, Scarring, and Phenotypes and Their Associated Risk Factors Among Young Chinese Adults

Introduction: Despite the high prevalence of acne vulgaris and its impact on affected individuals, few studies have provided a detailed characterization of acne phenotypes and their associated risk factors. This study aims to comprehensively evaluate the prevalence, severity, scarring, and phenotypes of acne, along with their associated risk factors, in a cohort of young Chinese adults, as part of the Singapore and Malaysia Cross-Sectional Genetic Epidemiology Study (SMCGES). Methods: Participants were randomly and consecutively recruited from universities in Singapore and Malaysia. Data on sociodemographic, familial medical histories of atopic diseases and acne, and lifestyle habits were collected using a validated investigator-administered questionnaire from 6225 young Chinese adults (mean age = 22.8 ± 5.7 years). A subset of participants underwent clinical assessment for acne severity (n = 2345), scarring grade (n = 2345), and phenotypes (n = 1191) by dermatologically trained personnel. Results: The prevalence of acne was 56.0%. Among acne cases (n = 3504), 38.5% had moderate-severe acne, 52.8% had scarring, 95.7% presented with blackhead and/or whitehead, and 55.8% had inflammatory phenotypes (e.g., papules, pustules, cysts and nodules). A parental history of acne emerged as the strongest risk factor associated with all acne phenotypes. Pet ownership (Adjusted odds ratio [AOR]: 1.403, 95% Confidence level [CI]: 1.131-1.744, p < 0.05) and occasional alcohol consumption (AOR: 1.328, 95% CI: 1.090-1.617, p < 0.05) were associated with a higher odd for blackhead and/or whitehead. Protective factors included higher parental education levels for acne scarring (AOR: 0.650, 95% CI: 0.459-0.904; p < 0.05), male gender (AOR: 0.365, 95% CI: 0.298-0.446; p < 0.05) and birthplace (AOR: 0.674, 95% CI: 0.555-0.819; p < 0.05) for non-inflammatory phenotypes. Conclusions: This study, conducted in a well-defined cohort of young Chinese adults from the SMCGES, reinforces familial history as a key risk factor for acne onset, severity, scarring, and phenotype manifestation. The identification of modifiable and environmental factors associated with acne phenotypes offers valuable insights for targeted interventions to improve acne management and control.引言：尽管寻常痤疮(acne vulgaris)患病率居高不下，且对患者造成显著不良影响，但目前鲜有研究对痤疮表型及其相关风险因素开展详细的特征化分析。本研究作为新马横断面遗传流行病学研究（Singapore and Malaysia Cross-Sectional Genetic Epidemiology Study, SMCGES）的一部分，旨在全面评估新加坡与马来西亚青年中国成年人队列中痤疮的患病率、严重程度、瘢痕形成情况及表型特征，并分析其相关风险因素。 方法：研究对象从新加坡及马来西亚的高校中随机连续招募。本研究采用经过验证的调查员施测问卷，对6225名青年中国成年人（平均年龄22.8±5.7岁）的社会人口学特征、特应性疾病及痤疮家族病史、生活习惯等信息进行采集。其中2345名受试者接受了痤疮严重程度与瘢痕分级评估，另有1191名受试者由经过皮肤科培训的专业人员完成痤疮表型的临床评估。 结果：痤疮总体患病率为56.0%。在3504名痤疮患者中，38.5%为中重度痤疮，52.8%存在痤疮瘢痕，95.7%表现为黑头粉刺或白头粉刺，55.8%存在炎性表型（如丘疹、脓疱、囊肿及结节）。父母痤疮病史是与所有痤疮表型相关的最强风险因素。养宠物（校正优势比[Adjusted odds ratio, AOR]=1.403，95%置信区间[Confidence interval, CI]=1.131~1.744，p<0.05）与偶尔饮酒（AOR=1.328，95%CI=1.090~1.617，p<0.05）与黑头/白头粉刺的发病风险升高显著相关。而痤疮瘢痕的保护因素包括父母更高的受教育水平（AOR=0.650，95%CI=0.459~0.904；p<0.05），非炎性痤疮表型的保护因素则为男性性别（AOR=0.365，95%CI=0.298~0.446；p<0.05）与出生地因素（AOR=0.674，95%CI=0.555~0.819；p<0.05）。 结论：本研究基于SMCGES队列中明确界定的青年中国成年人群体，进一步证实家族史是痤疮发病、严重程度、瘢痕形成及表型表现的关键风险因素。与痤疮表型相关的可干预及环境因素的识别，可为优化痤疮管理与防控的靶向干预策略提供重要参考价值。