. 2020 Apr 1;10:5754. doi: 10.1038/s41598-020-62715-3

Table 2.

List of risk factors for acne presentation analysed in the articles and results obtained for each risk factor.

Factor	Studies showing
Factor	Significant Risk Factor for Acne	Significant Protective Factor for Acne	Insignificant factor
Demographic
Age (increasing)	Aksu, et al., 2012; Hogewoning, et al., 2009; Karciauskiene, Valiukeviciene, Gollnick & Stang, 2014; Park, Kwon, Min, Yoon, & Suh, 2015; Schäfer, Nienhaus, Vieluf, Berger, & Ring, 2001; Wu, et al.⁵⁴;	Ali, et al.⁵⁰ (younger age); Wolkenstein, et al., 2018	Wei, et al., 2010
Computer usage	N/A	Wei, et al., 2010 (less than 2 h/day)	N/A
Job (Office worker)	Di Landro, **et al., 2016**	N/A	N/A
Marital status	N/A	Ali, et al.⁵⁰ (married)	N/A
Parent’s educational level	N/A	N/A	Bagatin, et al., 2014
Sex	Hogewoning, et al., 2009 (female); Rombouts, Nijsten & Lambert, 2006 (males); Schäfer, Nienhaus, Vieluf, Berger, & Ring, 2001 (male); Wei, et al., 2010 (male);	Ali, et al.⁵⁰ (male)	Aksu, et al., 2012; Park, Kwon, Min, Yoon, & Suh, 2015; Wolkenstein, et al., 2018
Socioeconomic status	N/A	N/A	Schäfer, Nienhaus, Vieluf, Berger, & Ring, 2001;
Years of education	N/A	N/A	Di Landro, **et al., 2016** (personal educational level); Duquia, et al., 2017
Genetic and/or Hormonal
Family History (parents with acne)	Al Hussein, et al., 2016; Karciauskiene, Valiukeviciene, Gollnick & Stang, 2014; Ismail, Manaf, & Azizan, 2012 (close relatives, eg: parents and siblings); Wolkenstein, et al., 2018	N/A	N/A
Family History (first-degree relatives with acne)	Di Landro, **et al., 2016; Goulden, McGeown, & Cunliffe, 1999; Ibrahim, Salem, El-Shimi, Baghdady & Hussein⁵⁷ (family members included not specified); Suppiah, et al.⁵⁹ (family members included not specified); Wang, et al., 2016** (family members included not specified); Wei, et al., 2010 (first- and second-degree relatives); Xu, et al.⁵⁵;	N/A	Bagatin, et al., 2014
Height	N/A	Duquia, et al., 2017 (short height)	Ismail, Manaf, & Azizan, 2012
Onset of puberty	Karciauskiene, Valiukeviciene, Gollnick & Stang, 2014;	Ali, et al.⁵⁰ (pre-menstrual stage)	Rombouts, Nijsten & Lambert, 2006
Pregnancy (never been pregnant)	Di Landro, *et al*., 2016	N/A	N/A
Personal history of acne in adolescence	Di Landro, *et al*., 2016	N/A	N/A
Regularity of menses	N/A	N/A	Di Landro, **et al., 2016*; Rombouts, Nijsten & Lambert, 2006; Wu, et al*.⁵⁴
Skin colour	N/A	Duquia, et al., 2017 (light skin phenotype)	Bagatin, et al., 2014
Skin type	Wang, **et al., 2016** (oily, mixed); Wei, et al., 2010 (oily/mixed); Wu, et al.⁵⁴ (oily/mixed/neutral);	Ali, et al.⁵⁰ (dry, normal, oily); Wei, et al., 2010 (dry/neutral);	N/A
Use of contraceptives (oral)	N/A	N/A	Di Landro, *et al., 2016; Goulden, McGeown, & Cunliffe, 1999*
Weight	N/A	N/A	Ismail, Manaf, & Azizan, 2012
Medical History
Anaemia	Wang, *et al*., 2016;	N/A	N/A
Anxiety	Wei, et al., 2010	N/A	N/A
Depression	Wei, et al., 2010	N/A	N/A
Dysmenorrhoea	Wei, et al., 2010	N/A	N/A
Familial diabetes	Lu, *et al., 2017; Skroza, et al*.⁵⁸;	N/A	N/A
Familial hypercholesterolemia	Skroza, *et al*.⁵⁸	N/A	N/A
Familial hypertension	Lu, *et al., 2017; Skroza, et al*.⁵⁸;	N/A	N/A
Family history of obesity	Lu, *et al*., 2017;	N/A	N/A
Hirsutism	Di Landro, *et al*., 2016	N/A	N/A
Hypertrichosis	Wang, *et al*., 2016;	N/A	N/A
Menstrual Disorder	Wang, *et al., 2016; Wei, et al*., 2010	N/A	N/A
Psychological disorder	Wang, et al., 2016;	N/A	N/A
Diet
Diet (general)	Ibrahim, Salem, El-Shimi, Baghdady & Hussein⁵⁷	N/A	Ismail, Manaf, & Azizan, 2012 (energy intake);
Carbonated drink intake	Al Hussein, et al., 2016;	N/A	Karciauskiene, Valiukeviciene, Gollnick & Stang, 2014 (lemonade); Suppiah, *et al.⁵⁹; Wolkenstein, et al., 2015; Wolkenstein, et al*., 2018
Dairy intake	Adebamowo, et al., 2008 (skim milk only); Ismail, Manaf, & Azizan, 2012 (frequent intake of milk and ice cream); Suppiah, *et al*.⁵⁹ (milk);	N/A	Adebamowo, et al., 2008 (dairy fat, dairy other than milk, total milk, whole milk, low-fat milk); Al Hussein, et al., 2016 (milk, cheese, yoghurt); Di Landro, *et al., 2016; Duquia, et al., 2017 (whole milk, low fat milk, cheese, yoghurt); Ismail, Manaf, & Azizan, 2012* (cheese and yoghurt); Karciauskiene, Valiukeviciene, Gollnick & Stang, 2014; Suppiah, *et al.⁵⁹ (ice cream, yoghurt); Wolkenstein, et al., 2015; Wolkenstein, et al*., 2018 (dairy in general, milk, type of milk and ice cream);
Fast food intake	Aksu, et al., 2012 (high intake of sausages and cakes); Wei, et al., 2010;	N/A	Adebamowo, et al., 2008 (French fries and pizza); Karciauskiene, Valiukeviciene, Gollnick & Stang, 2014 (hamburgers and pizza); Park, Kwon, Min, Yoon, & Suh, 2015 (pizza); Wolkenstein, et al., 2015;
Fat intake	Aksu, et al., 2012; Al Hussein, et al., 2016; Wang, **et al., 2016** (fatty food); Wei, et al., 2010	N/A	Adebamowo, et al., 2008 (total fat, types of fat); Ismail, Manaf, & Azizan, 2012; Suppiah, *et al.⁵⁹ (potato chips); Wu, et al*.⁵⁴;
Fish intake	Di Landro, *et al., 2016 (low intake of fish); Wang, et al*., 2016 (seafood);	Al Hussein, et al., 2016;	Karciauskiene, Valiukeviciene, Gollnick & Stang, 2014; Wu, et al.⁵⁴ (seafood);
Fruits and vegetables intake	Di Landro, *et al*., 2016 (low intake of fruits and vegetables);	Aksu, et al., 2012; Al Hussein, et al., 2016; Wei, et al., 2010 (frequent fruit intake only, not vegetables);	Ismail, Manaf, & Azizan, 2012 (fibre); Karciauskiene, Valiukeviciene, Gollnick & Stang, 2014; Wolkenstein, et al., 2018 (fruit juice);
Glycaemic load	Ismail, Manaf, & Azizan, 2012 (high)	N/A	N/A
Intake of rice/pasta/ semolina	N/A	N/A	Wolkenstein, et al., 2018
Irregular meals	N/A	N/A	Al Hussein, et al., 2016
Lack of nutritional information	N/A	N/A	Al Hussein, et al., 2016
Meat intake	N/A	N/A	Di Landro, *et al., 2016 (beef); Ismail, Manaf, & Azizan, 2012* (protein); Karciauskiene, Valiukeviciene, Gollnick & Stang, 2014; Park, Kwon, Min, Yoon, & Suh, 2015;
Mediterranean diet (high intake of legumes, grains, fish, olive oil, fruits, vegetables and nuts; low intake of meat; moderate intake of milk, dairy products and alcohol)	N/A	Skroza, *et al*.⁵⁸	N/A
Nut intake	N/A	N.A	Ismail, Manaf, & Azizan, 2012; Suppiah, *et al*.⁵⁹;
Spicy food intake	Wei, et al., 2010	Ali, et al.⁵⁰ (intake of non-spicy food)	N/A
Sugar/chocolates intake	Aksu, et al., 2012 (high sugar intake, high intake of pastries and cakes); Al Hussein, et al., 2016 (sweets); Park, Kwon, Min, Yoon, & Suh, 2015; Suppiah, *et al.⁵⁹ (chocolate); Wang, et al., 2016; Wolkenstein, et al., 2015; Wolkenstein, et al*., 2018 (chocolate)	N/A	Adebamowo, et al., 2008; Di Landro, *et al., 2016 (cakes, chocolate, sweets, high-starch foods); Duquia, et al., 2017; Ismail, Manaf, & Azizan, 2012* (chocolate, carbohydrates); Karciauskiene, Valiukeviciene, Gollnick & Stang, 2014 (sweets); Suppiah, *et al.⁵⁹ (sweets); Wolkenstein, et al., 2018 (sweets); Wu, et al*.⁵⁴ (sweet food);
Vitamin and mineral intake	N/A	N/A	Adebamowo, et al., 2008 (vitamin A, vitamin D and calcium); Ismail, Manaf, & Azizan, 2012 (vitamin A, vitamin E, zinc, selenium); Rombouts, Nijsten & Lambert, 2006 (multivitamin)
White bread intake	Al Hussein, et al., 2016;	N/A	N/A
BMI (overweight/obese)	Aksu, et al., 2012; Al Hussein, et al., 2016; Hogewoning, et al., 2009; Karciauskiene, Valiukeviciene, Gollnick & Stang, 2014; Lu, *et al*., 2017; Park, Kwon, Min, Yoon, & Suh, 2015;	N/A	Duquia, et al., 2017; Ismail, Manaf, & Azizan, 2012 (as well as body fat percentage); Wolkenstein, et al., 2015; Wolkenstein, et al., 2018
Substance Use
Alcohol intake	N/A	N/A	Di Landro, *et al., 2016; Karciauskiene, Valiukeviciene, Gollnick & Stang, 2014; Schäfer, Nienhaus, Vieluf, Berger, & Ring, 2001; Wolkenstein, et al., 2015; Wolkenstein, et al*., 2018;
Cannabis use	Wolkenstein, et al., 2015;	N/A	Wolkenstein, et al., 2018
Drug usage	N/A	N/A	Rombouts, Nijsten & Lambert, 2006
Number of cigarettes smoked/day	Schäfer, Nienhaus, Vieluf, Berger, & Ring, 2001 (dose-dependent relationship);	Rombouts, Nijsten & Lambert, 2006 (females)	Rombouts, Nijsten & Lambert, 2006 (males)
Smoking duration	N/A	Rombouts, Nijsten & Lambert, 2006 (females)	Rombouts, Nijsten & Lambert, 2006 (males)
Smoking status (cigarettes)	Al Hussein, et al., 2016; Ibrahim, Salem, El-Shimi, Baghdady & Hussein⁵⁷; Schäfer, Nienhaus, Vieluf, Berger, & Ring, 2001;	Rombouts, Nijsten & Lambert, 2006 (females)	Di Landro, *et al., 2016; Duquia, et al., 2017; Karciauskiene, Valiukeviciene, Gollnick & Stang, 2014; Rombouts, Nijsten & Lambert, 2006 (males); Suppiah, et al*.⁵⁹
Tobacco use	N/A	Wolkenstein, et al., 2015; Wolkenstein, et al., 2018;	N/A
Living Environment, Stress and Emotional factors
Country of residence	Wolkenstein, et al., 2018 (living in Czech Republic or Slovak Republic)	Wolkenstein, et al., 2018 (living in Poland or Belgium)	N/A
Insomnia	Wei, et al., 2010 (frequent)	N/A	N/A
Living environment (Urban/rural)	Hogewoning, et al., 2009 (urban);	Aksu, et al., 2012 (urban)	Al Hussein, et al., 2016;
Mental stress	Di Landro, *et al., 2016; Ibrahim, Salem, El-Shimi, Baghdady & Hussein⁵⁷; Wei, et al*., 2010;	N/A	N/A
Physical exercise	N/A	N/A	Rombouts, Nijsten & Lambert, 2006
Sleep duration (lack of sleep)	Wang, *et al., 2016 (less than 8 h); Wei, et al., 2010 (less than 8 h); Wu, et al*.⁵⁴;	N/A	Park, Kwon, Min, Yoon, & Suh, 2015 (less than 9 h);
Study pressure	Wei, et al., 2010	N/A	N/A
Sun exposure	Ibrahim, Salem, El-Shimi, Baghdady & Hussein⁵⁷	N/A	N/A
Sunbed usage	N/A	N/A	Rombouts, Nijsten & Lambert, 2006
Skincare
Frequency of face washing/day	N/A	Aksu, et al., 2012 (with tap water)	Park, Kwon, Min, Yoon, & Suh, 2015 (with cleanser);
Use of moisturisers/ cosmetics	Wu, et al.⁵⁴;	N/A	Park, Kwon, Min, Yoon, & Suh, 2015;

Study design is indicated via text colour. Black text indicates a cross-sectional design, italic text indicates a longitudinal design and bold text indicates a case-control design.