Epidemiology of Acne Vulgaris in 18-Year-Old Male Army Conscripts in a South Brazilian City

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1 Original Paper Received: July 6, 2016 Accepted after revision: April 16, 2017 Published online: June 14, 2017 Epidemiology of Acne Vulgaris in 18-Year-Old Male Army Conscripts in a South Brazilian City Rodrigo Pereira Duquia a, b Iná da Silva dos Santos a Hiram de Almeida Jr. b, c Paulo Ricardo Martins Souza d Juliano de Avelar Breunig e Christos C. Zouboulis f a Postgraduate Program in Epidemiology, and b Department of Dermatology, Federal University of Pelotas, and c Department of Dermatology, Catholic University of Pelotas, Pelotas, d Postgraduation Program in Dermatology, Santa Casa of Porto Alegre, Porto Alegre, and e Department of Dermatology, University of Santa Cruz do Sul, Santa Cruz do Sul, Brazil; f Departments of Dermatology, Venereology, Allergology, and Immunology, Dessau Medical Center, Brandenburg Medical School, Dessau, Germany Keywords Acne Prevalence Adolescents Male gender Ethnic skin Risk factors Body height Nutrition Abstract Background: Prevalence of acne varies worldwide. Several factors (age, skin color, body fat, diet, and smoking) have been investigated as risk factors. Objective: A total of 2, year-old males living in Pelotas, South Brazil, were evaluated in order to examine the prevalence of acne and associated factors. Methods: A cross-sectional population-based study was conducted. A dermatologist performed the clinical examination of the face and trunk for identification of acne lesions. Acne was evaluated as clinically noninflammatory, inflammatory, and acne with both types of lesions. Skin color, schooling, height, smoking, skinfolds, waist circumference, BMI, and dietary dairy intake were the independent variables used. Results: A response rate of 97.2% was ob- tained. Individuals without any acne lesion were 241 (10.9%); 161 (7.3%) only had noninflammatory lesions, 404 (18.4%) only inflammatory lesions; and 1,395 (63.4%) presented both types of lesions. In multivariate analysis, the type of lesions was different in light and dark skin phototype adolescents, with more common inflammatory lesions in the light phototype and noninflammatory ones in the dark phototype patients. Height was directly associated with the occurrence of all types of acne, whereas lower fat mass was associated with the occurrence of noninflammatory acne. While daily consumption of whole milk or yogurt was found to be associated with inflammatory acne in crude analysis, the association with milk was not detected and that with yogurt was low in multivariate analysis. Conclusion: Our results suggest that future studies should explore determinants of noninflammatory and inflammatory acne separately, especially if mixed populations are studied S. Karger AG, Basel karger@karger.com S. Karger AG, Basel Prof. Dr. med. Prof. h.c. Dr. h.c. Christos C. Zouboulis Departments of Dermatology, Venereology, Allergology, and Immunology Dessau Medical Center, Theodore Fontane Medical University of Brandenburg Auenweg 38, DE Dessau (Germany) klinikum-dessau.de

2 Introduction Acne vulgaris is a distressing condition involving the so-called sebaceous follicle [1]. It is mainly considered an adolescent disorder and is characterized by spontaneous resolution in the late teens or early twenties in the majority of cases, in some of them with facial scar formation [2]. Prevalence of acne varies worldwide: studies published in the last decade reported prevalence ranging from 25.2%, among prepubertal children in Peru to 93.2 and 93.3% among adolescents in Iran and Australia [3]. A series of methodological aspects, including definition of the disease (type and location of the lesions) and demographic characteristics of the studied population may be responsible for discrepancies in the prevalence of the disease in different investigations. Indeed, in some studies, a single closed or open comedone was sufficient to consider the subject as a patient with acne, while in others more than 20 inflammatory and noninflammatory lesions were required to diagnose the subject as having acne [4]. Several factors (age, skin color, body fat, diet, and smoking) have been investigated as risk factors for acne. In most studies, diet and body fat have been shown to be associated with the disease [5 12]. However, one study showed a statistically significant association between higher body fat and acne [9], while another found a protective effect [13]. Other factors, such as skinfolds, height, and waist circumference, have not shown to be consistently associated with acne [14]. Comedones are considered the earliest acne lesion [1]. They may become inflamed, producing tender papules that may progress to pustules and, in severe cases, to nodules and cysts [15]. Papules and pustules can occur without the presence of comedones [16] ; however, the majority of the patients present both comedones and papules/ pustules. Interestingly, although comedones are clinically considered noninflammatory lesions, they exhibit subclinical signs of inflammation [17]. The objective of this investigation was to measure the prevalence of individuals with clinically noninflammatory, inflammatory and with both types of acne lesions, as well as to identify factors independently associated with each subtype of acne presentation through a populationbased study of 18-year-old males living in Pelotas, Southern Brazil. Patients and Methods For further details, see the online supplementary material (see for all online suppl. material) (Fig. 1 ). Adolescents enlisted in the army n = 2,264 Lost/refusal n = 63 Adolescent interview n = 2,201 Adolescents without acne lesion n = 241 (10.9%) Adolescents with any acne lesion n = 1,960 (88.9%) Fig. 1. Flowchart of the distribution of acne subsets. Adolescents with only noninflammatory lesions n = 161 (7.3%) Adolescents with only inflammatory lesions n = 404 (18.4%) Adolescents with inflammatory and noninflammatory lesions n = 1,395 (63.4%) 146 Pereira Duquia et al.

3 Table 1. Description of individuals without acne and individuals with noninflammatory only, inflammatory only, and both types of acne lesions Variable Individuals with no acne lesions Individuals with only noninflammatory lesions Individuals with only inflammatory lesions Individuals with inflammatory and noninflammatory lesions Skin color Light skin phenotype Dark skin phenotype Schooling, years Height in tertiles Smoking TSF in tertiles SSF in tertiles Waist circumference (tertiles) BMI Cheese (daily) Whole milk (daily) Low fat milk (daily) Yogurt (daily) Powder chocolate (daily) Chocolate bar (daily) 147 (61.0) 94 (39.0) 142 (58.9) 99 (41.1) 113 (46.9) 70 (29.1) 58 (24.1) 194 (80.5) 47 (19.5) 82 (34.0) 70 (29.1) 89 (36.9) 78 (32.4) 76 (31.5) 87 (36.1) 85 (35.3) 63 (26.1) 93 (38.6) 80 (33.3) 70 (29.2) 90 (37.5) 192 (79.7) 49 (20.3) 158 (65.6) 83 (34.4) 226 (93.8) 15 (6.2) 223 (92.5) 18 (7.5) 163 (67.6) 78 (32.4) 218 (90.5) 23 (9.5) 76 (47.2) 85 (52.8) 98 (60.9) 63 (39.1) 59 (36.7) 51 (31.7) 51 (31.7) 135 (83.9) 26 (16.2) 78 (48.5) 42 (26.1) 41 (25.5) 63 (39.1) 51 (31.7) 47 (29.2) 54 (33.5) 60 (37.3) 47 (29.2) 58 (36.0) 57 (35.4) 46 (28.6) 131 (81.4) 30 (18.6) 108 (67.1) 53 (32.9) 154 (95.7) 7 (4.4) 143 (88.8) 18 (11.2) 121 (75.2) 40 (24.8) 146 (90.7) 15 (9.3) 291 (72.0) 113 (28.0) 213 (52.7) 191 (47.3) 147 (36.4) 140 (34.6) 117 (29.0) 341 (84.4) 63 (15.6) 112 (27.7) 148 (36.6) 144 (35.6) 125 (30.9) 131 (32.4) 148 (36.6) 120 (29.8) 126 (31.3) 157 (39.0) 115 (28.5) 131 (32.5) 157 (39.0) 311 (77.2) 92 (22.8) 232 (57.4) 172 (42.6) 373 (92.3) 31 (7.7) 361 (89.4) 43 (10.6) 259 (64.1) 145 (35.9) 372 (92.1) 32 (7.9) Total ,395 1,039 (74.5) 356 (25.5) 685 (49.1) 710 (50.9) 502 (36.0) 467 (33.5) 426 (30.5) 1,211 (86.1) 184 (13.2) 467 (33.5) 477 (34.2) 451 (32.3) 470 (33.7) 479 (34.3) 446 (32.0) 481 (34.5) 477 (34.2) 436 (31.3) 480 (34.5) 474 (34.0) 439 (31.5) 1,063 (76.2) 332 (23.8) 777 (55.7) 618 (44.3) 1,300 (93.2) 95 (6.8) 1,233 (88.4) 162 (11.6) 868 (62.2) 527 (37.8) 1,266 (90.8) 129 (9.2) Data are presented as n (%). TSF, triceps skinfold; SSF, subscapular skinfold; BMI, body mass index. Epidemiology of Acne in Males in Southern Brazil 147

4 Table 2. Prevalence and crude and adjusted prevalence ratios (PR) for noninflammatory acne only according to independent variables Variable Prevalence, % Crude PR Adjusted PR Skin color a c 0.04 c Light skin phenotype Dark skin phenotype ( ) 1.29 ( ) Schooling 0.8 a 0.7 c 0.7 c 0 8 years 9 years ( ) 1.05 ( ) Height in tertiles 0.03 b 0.03 d 0.02 d ( ) 1.36 ( ) 1.26 ( ) 1.39 ( ) Smoking 0.4 a 0.4 c 0.3 c ( ) 0.84 ( ) TSF in tertiles b d d ( ) 0.65 ( ) 0.78 ( ) 0.64 ( ) SSF in tertiles 0.1 b 0.1 d 0.9 d ( ) 0.79 ( ) 0.95 ( ) 1.07 ( ) Waist circumference (tertiles) 0.4 b 0.4 d 0.6 d ( ) 0.86 ( ) 1.24 ( ) 1.04 ( ) BMI 0.2 b 0.2 d 0.7 d ( ) 0.81 ( ) 1.09 ( ) 0.88 ( ) Cheese (daily) 0.7 a 0.7 c 0.7 c ( ) 1.06 ( ) Whole milk (daily) 0.8 a 0.8 c 0.3 c ( ) 1.18 ( ) Low fat milk (daily) 0.5 a 0.5 c 0.9 c ( ) 0.96 ( ) Yogurt (daily) 0.2 a 0.2 c 0.2 c ( ) 1.28 ( ) Powder chocolate (daily) 0.1 a 0.1 c 0.1 c ( ) 0.81 ( ) Chocolate bar (daily) 1.0 a 0.9 c 0.7 c ( ) 0.91 ( ) TSF, triceps skinfold; SSF, subscapular skinfold; BMI, body mass index. a χ 2 test. b Linear trend test. c Heterogeneity Wald test. d Wald linear trend test. 148 Pereira Duquia et al.

5 Table 3. Prevalence and crude and adjusted prevalence ratios (PR) for inflammatory acne only according to independent variables Variable Prevalence, % Crude PR Adjusted PR Skin color a c c Light skin phenotype Dark skin phenotype ( ) 0.83 ( ) Schooling 0.1 a 0.1 c 0.8 c 0 8 years 9 years ( ) 1.02 ( ) Height in tertiles 0.02 b 0.02 d 0.03 d ( ) 1.18 ( ) 1.18 ( ) 1.17 ( ) Smoking 0.2 a 0.2 c 0.5 c ( ) 0.94 ( ) TSF in tertiles 0.5 b 0.5 d 0.9 d ( ) 1.07 ( ) 1.11 ( ) 0.97 ( ) SSF in tertiles 0.8 b 0.8 d 0.6 d ( ) 1.02 ( ) 0.99 ( ) 0.95 ( ) Waist circumference (tertiles) 0.4 b 0.4 d 0.8 d ( ) 1.07 ( ) 1.07 ( ) 0.97 ( ) BMI 0.4 b 0.4 d 0.5 d ( ) 1.08 ( ) 1.09 ( ) 1.06 ( ) Cheese (daily) 0.5 a 0.5 c 0.9 c ( ) 1.01 ( ) Whole milk (daily) 0.05 a 0.04 c 0.2 c ( ) 1.09 ( ) Low fat milk (daily) 0.5 a 0.5 c 0.4 c ( ) 1.09 ( ) Yogurt (daily) 0.2 a 0.1 c 0.2 c ( ) 1.14 ( ) Powder chocolate (daily) 0.4 a 0.4 c 0.4 c ( ) 0.93 ( ) Chocolate bar (daily) 0.5 a 0.5 c ( ) 0.92 ( ) TSF, triceps skinfold; SSF, subscapular skinfold; BMI, body mass index. a χ 2 test. b Linear trend test. c Heterogeneity Wald test. d Wald linear trend test. 0.5 c Epidemiology of Acne in Males in Southern Brazil 149

6 Results A total of 2,264 adolescents were enlisted in the army. Of these, 63 (2.8%) did not attend the medical examination. The remaining 2,201 adolescents were invited and agreed to participate in the study ( Fig. 1 ). Individuals without any acne lesion were 241 (10.9%); 161 (7.3%) only had noninflammatory lesions; 404 (18.4%) only had inflammatory lesions; and 1,395 (63.4%) had both noninflammatory and inflammatory lesions ( Fig. 1 ). Table 1 describes the four subgroups of individuals (no acne lesions, only noninflammatory lesions, only inflammatory lesions, and both types of lesions). There were more patients with a light skin phenotype than with a dark skin phenotype among those with inflammatory lesions alone or in combination with noninflammatory lesions. Among the subjects with noninflammatory lesions only, the proportion of patients with light and dark skin phenotypes was similar (52.8 and 47.2%, respectively). Among individuals without acne, the proportion of patients with a light skin phenotype was markedly higher than the proportion of patients with a dark skin phenotype (61 and 39%, respectively). The proportion of shorter adolescents (first tertile in height) was higher among those without acne than among individuals from the 3 case groups. There were more thin adolescents of the first tertile in triceps skinfold (TSF), subscapular skinfold, and BMI in the noninflammatory group than among the others. The four groups were similar with regard to daily consumption of cheese, milk, yogurt, and chocolate. Table 2 shows the prevalence of individuals with noninflammatory lesions only as well as crude and adjusted prevalence ratios (PR) with corresponding 95% CI according to independent variables. In the crude analysis, the prevalence of comedonal acne alone was higher among adolescents with a dark skin phenotype, and those who were taller and thinner. These results were confirmed in multivariate analysis. The probability of noninflammatory acne was 29% higher in the dark than in the light skin phenotype individuals. The occurrence increased linearly with the adolescent height and inversely with TSF: the taller and the thinner the adolescent was, the higher was the probability of having noninflammatory acne. Comparatively to the shortest adolescents (first tertile) taken as the reference group, those in the second and third tertiles had a higher probability of 26 and 39%, respectively, of presenting noninflammatory acne. The lower the TSF was, the higher was the probability of only having noninflammatory acne. There was no association between noninflammatory acne and school attainment, smoking, daily consumption of milk, dairy products or chocolate, or with the remaining body fat indicators (subscapular skinfold, BMI, and waist circumference). Table 3 presents the prevalence of individuals with only inflammatory lesions according to the independent variables. In crude analysis, the prevalence of inflammatory acne alone increased with height and was greater among adolescents with a light skin phenotype and among those who reported daily consumption of whole milk. There was no association between inflammatory lesions and the other variables. In multivariate analysis, only skin color and height remained associated with inflammatory lesions. Adolescents with a light skin phenotype had a 17% higher probability than those with a dark skin phenotype of presenting inflammatory acne. Inflammatory acne was also directly associated with adolescent height. Taller adolescents had a 17% higher probability of presenting inflammatory acne alone than their counterparts from the shorter group (first tertile). Table 4 shows the results from patients with both types of acne lesions. In crude analysis, the prevalence of acne was greater among patients with a light skin phenotype and increased with years of schooling and adolescent height. Prevalence was also higher among nonsmokers and among those who reported daily consumption of whole milk and yogurt. In multivariate analysis, only skin color, height, and daily consumption of yogurt remained associated with acne. The probability of presenting both types of lesions was 9% higher in adolescents with a light skin phenotype in comparison to those with a dark skin phenotype. Daily consumers of yogurt had a 5% higher probability of presenting acne than their counterparts. The association with height was similar to the findings observed with the above subgroups, with the probability of occurrence directly increasing with the adolescent s height. Discussion The measured prevalence of 89% is the real prevalence of acne (all types) in 18-year-old male adolescents in the city of Pelotas, Brazil. This finding is in agreement with results from Australia, Nigeria, Peru, and Turkey [3, 18 22] (Table 5 ). The method of classification of acne and the area of skin evaluated varied in different studies, making the comparison between the available studies difficult. Moreover, high rate of losses found in some of the studies, may 150 Pereira Duquia et al.

7 Table 4. Prevalence and crude and adjusted prevalence ratios (PR) for associated noninflammatory and inflammatory acne according to independent variables Variables Prevalence, % Crude PR Adjusted PR Skin color <0.001 a <0.001 c <0.001 c Light skin phenotype Dark skin phenotype ( ) 0.91 ( ) Schooling a c 0.2 c 0 8 years 9 years ( ) 1.03 ( ) Height in tertiles b d d ( ) 1.08 ( ) 1.06 ( ) 1.07 ( ) Smoking 0.01 a 0.02 c 0.06 c ( ) 0.94 (0.88 ) TSF in tertiles 0.5 b 0.5 d 0.6 d ( ) 0.98 ( ) 1.01 ( ) 0.98 ( ) SSF in tertiles 0.3 b 0.3 d 0.8 d ( ) 0.98 ( ) ( ) 1.01 ( ) Waist circumference (tertiles) 0.3 b 0.3 d 0.07 d ( ) 0.97 ( ) 1.03 ( ) 0.95 (0.90 ) BMI 0.2 b 0.2 d 0.7 d ( ) 0.97 ( ) 1.01 ( ) 1.01 ( ) Cheese (daily) 0.3 a 0.2 c 0.7 c ( ) 1.01 ( ) Whole milk (daily) a c 0.06 c ( ) 1.04 ( 1.08) Low fat milk (daily) 0.9 a 0.7 c 0.7 c ( ) 1.02 ( ) Yogurt (daily) 0.06 a 0.03 c 0.05 c ( ) 1.05 ( 1.11) Powder chocolate (daily) 0.1 a 0.1 c 0.3 c ( ) 0.98 ( ) Chocolate bar (daily) 0.9 a 0.9 c 1.0 c ( ) ( ) TSF, triceps skinfold; SSF, subscapular skinfold; BMI, body mass index. a χ 2 test. b Linear trend test. c Heterogeneity Wald test. d Wald linear trend test. Epidemiology of Acne in Males in Southern Brazil 151

8 Table 5. Prevalence of acne vulgaris in 18-year-old males; review of large studies worldwide Country n Prevalence, % Type of study Reference Australia CB, Q, CE [18] Brazil 2, CB, CE This study Iran CB, Q, CE [3] Mali CB, P [22] Nigeria CB, Q, CE [19] Peru CB, Q, CE [20] Turkey CB, Q, CE [21] CB, community-based; CE, clinical examination; Q, questionnaire; P, photograph evaluation. have biased the prevalence and the associations found [23 26]. Besides sample size, methodological strengths of the current study include standardization of skin examination and of anthropometric measures, and the high intraand interobserver agreement rate obtained in type and counting of acne lesions and of anthropometric measures. The process of calibration increased the accuracy of the measures, contributing to the quality of the analysis. Moreover, skin examination performed by dermatologists, as in the current study, is a methodological advantage over self-reported acne because self-perception of having acne may depend of individual subjective values. At last, the subgroup analyses are an issue not addressed in a number of previous studies [27]. Homogeneity of the adolescent age, the fact that only males were examined, and the cross-sectional nature of the study are limitations of this work. In the literature, skin color was reported to be associated with increased acne rates [7]. Our study showed a consistent association between skin color and acne. In crude and adjusted analyses, light skin phenotype was protective against the presence of noninflammatory acne alone, whereas light skin phenotype was a risk factor for inflammatory acne. Litman et al. [8] identified that dark skin phenotype men had higher dihydrotestosterone levels and dihydrotestosterone/testosterone ratio when compared with patients with a light skin phenotype and Hispanic men. This higher level of androgens may affect the prevalence of acne in dark skin phenotype persons [8]. Our study showed a difference in the direction of the associations found between acne and skin color. Height of the individuals had a positive association with acne in all three groups evaluated. Since taller adolescents may have had epiphyseal ossification later than the shorter ones and since the androgens are among the main factors involved in this process, it is possible that a later exposure to androgens close to the 18th year of age may be responsible for the highest prevalence of acne observed in this group. Smoking was reported to be a clinically important contributor to acne prevalence, severity, and type [6, 28]. Recent investigations revealed that cigarette smoke contains high amounts of arachidonic acid and polycyclic aromatic hydrocarbons, which induce a phospholipase A2-dependent inflammatory pathway; this effect may further stimulate arachidonic acid synthesis. On the other hand, smokers may have a higher saturated fat intake with their food and much lower polyunsaturated fat intake, principally due to a lower linoleic acid intake compared with nonsmokers, as reported by Zouboulis et al. [5]. In an experimental study, topically applied linoleic acid was shown to induce an almost 25% reduction in the overall size of microcomedones over a 1-month treatment period [29]. However, in all three subgroups of our study, the prevalence of acne was higher among nonsmokers. The small number of teenage smokers in each subgroup analysis may have affected the assessment of the relationship between smoking and acne. Some studies suggested that Western diet with characteristically high glycemic index leads to hyperinsulinemia and a resulting cascade of endocrine consequences which may mediate acne pathogenesis [11]. Cordain et al. [30] and Kaymak et al. [31] suggested that hyperinsulinemia elicits endocrine responses that may affect the development of acne through mediators, such as androgens insulin-like growth factor (IGF)-I, IGFbinding protein 3, and retinoid signaling pathways. The role of diet in endocrine activity is supported by the observation that improvements in nutrition have been linked to an earlier onset of sexual maturation and the development of acne in young girls and boys. Furthermore, in the last years, some studies have linked acne to milk intake [10, 32]. If acne is due to hyperinsulinemia, it would be expected that obese individuals, who are relatively chronically insulin resistant, would present a higher prevalence of acne [30, 31]. In a cross-sectional population-based study with children aged 6 11 years, the BMI in acne children was significantly higher than that in children without acne [9]. In our study, we used waist circumference and BMI as markers of insulin resistance, and no association was found in all acne subgroups. However, although widely used to make estimates of body fat, several studies 152 Pereira Duquia et al.

9 have shown that BMI is not an accurate measurement of body composition, since it does not accurately distinguish body fat from lean mass. In order to further estimate the body fat mass, we evaluated skinfolds, which is likely to be a more reliable indicator. Individuals with lower fat mass, as measured by TSF, had a higher rate of noninflammatory acne than the ones with higher fat mass, in crude and adjusted analyses. association of this variable was found with exclusively inflammatory acne or in those with both types of lesions. Association between acne and food consumption (sweets, chocolate, oily foods, and nuts) have been explored in several studies [3, 12, 32, 33], some of them showed statistically significant associations [3, 33]. However, in the majority of the studies, presence of acne was self-reported by the interviewed persons, which may affect the outcome classification and, therefore, the internal validity of the studies [4]. As stated above, self-reported acne may be affected by the relative relevance given by each individual to the presence of a skin lesion. In our study, daily consumption of yogurt was associated with the simultaneous presence of noninflammatory and inflammatory lesions in crude and adjusted analyses. The association between daily consumption of whole milk and inflammatory acne was only present in crude analysis. Although the results of adjusted analyses were not statistically significant, the prevalence ratios for daily consumption of whole milk may point to a weak positive association with inflammatory acne. Daily chocolate consumption was not associated with any kind of acne lesions [3]. The statistical power of the study for two subgroups (noninflammatory or inflammatory only) was limited due to the small size of the samples. Other studies with greater sample sizes may be necessary to afford sufficient power to detect small associations. In summary, our findings show that acne is highly prevalent among adolescent males in Southern Brazil and that most of the adolescents exhibit simultaneously both types (noninflammatory and inflammatory) of lesions. Skin color was consistently associated with acne occurrence in all three subgroups, but the type of lesions was different in adolescents with light and dark skin phenotypes (inflammatory lesions in the former and noninflammatory in the latter group). Height was directly associated with the occurrence of all types of acne, whereas lower fat mass was associated with the occurrence of noninflammatory acne. Daily consumption of whole milk or yogurt may be associated with inflammatory acne. Our results suggest that future studies should explore determinants of noninflammatory and inflammatory acne separately. Key Message Male adolescents in Brazil present a high prevalence of acne (89.1%), mostly with both inflammatory and noninflammatory lesions. Inflammatory lesions are more prominent in light phototype patients, while noninflammatory ones in dark phototype adolescents. Height is directly associated with the occurrence of acne. Statement of Ethics The study protocol was approved by the Ethics Committee of the Faculty of Medicine of Federal University of Pelotas and adhered to the Declaration Helsinki guidelines. Written informed consent was obtained from each participant before enrolling in the study. Disclosure Statement All authors declare no conflict of interest. References 1 Moradi-Tuchayi S, Makrantonaki E, Ganceviciene R, Dessinioti C, Feldman S, Zouboulis CC: Acne vulgaris. Nature Rev Dis Primers 2015; 1: Bhate K, Williams HC: What s new in acne? An analysis of systematic reviews published in Clin Exp Dermatol 2014; 39: Ghodsi SZ, Orawa H, Zouboulis CC: Prevalence, severity and severity risk factors of acne in high school pupils: a community-based study. J Invest Dermatol 2009; 129: Daniel F, Dreno B, Poli F, et al: Descriptive epidemiological study of acne on scholar pupils in France during autumn 1996 (in French). Ann Dermatol Venereol 2000; 127: Zouboulis CC, Eady A, Philpott M, Goldsmith LA, Orfanos CE, Cunliffe WC, Rosenfield R: What is the pathogenesis of acne? Exp Dermatol 2005; 14: Schafer T, Nienhaus A, Vieluf D, Berger J, Ring J: Epidemiology of acne in the general population: the risk of smoking. Br J Dermatol 2001; 145: Taylor SC, Cook-Bolden F, Rahman Z, Strachan D: Acne vulgaris in skin of color. J Am Acad Dermatol 2002; 46:S98 S Litman HJ, Bhasin S, Link CL, Araujo AB, McKinlay JB: Serum androgen levels in black, hispanic, and white men. J Clin Endocrinol Metab 2006; 91: Tsai MC, Chen W, Cheng YW, Wang CY, Chen GY, Hsu TJ: Higher body mass index is a significant risk factor for acne formation in schoolchildren. Eu J Dermatol 2006; 16: Epidemiology of Acne in Males in Southern Brazil 153

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