Abstract
BACKGROUND: The epidemiological evaluation of androgenetic alopecia (AGA) is based mainly on direct observation and questionnaires. The international epidemiology and environmental risk factors of AGA in young Caucasian men remain unknown. AIM: To use photographs and data from the Internet to evaluate severe AGA and generate greater understanding of the international epidemiology of the disorder in young Caucasian men. MATERIALS AND METHODS: A population-based cross-sectional study design was used. The sample included 26,340 Caucasian men aged 30 to 40 years who had uploaded profiles to two dating websites. Their photographs were evaluated for AGA and graded as follows: severe AGA (Norwood type VI-VII), non-severe AGA, and unknown. Epidemiological data were collected from the sites. Logistic regression was used to analyze the effect of risk factors on the prevalence of severe AGA. RESULTS: The overall success rate for identifying severe AGA by indirect evaluation of Internet photographs was 94%. The prevalence of severe AGA was 15.33% overall and varied significantly by geographical region. The risk of having severe AGA was increased by 1.092 for every year of age between 30 and 40 years. Severe AGA was more prevalent in subjects with higher body mass index. CONCLUSIONS: Photographs from the Internet can be used to evaluate severe AGA in epidemiological studies. The prevalence of severe AGA in young Caucasian men increases with age and varies by geographical region. Body mass index is an environmental risk factor for severe AGA.