Background: Although psoriasis occurs worldwide, the prevalence varies considerably between different peoples and regions. In China, a questionnaire-based study was carried out in 1987 and the prevalence of psoriasis was found to be 0.12%. Since then, no large-scale, populationbased study has been reported. Objectives: To obtain the accurate figures for the prevalence of psoriasis in China. Methods: A population-based survey was conducted in 6 cities. The cluster sampling method was used to select communities in each city. The subjects were required to fill out self-reporting questionnaires during a face-to-face interview and also received physical examination by dermatologists. Results: 19,974 subjects were visited and 17,345 completed the questionnaires and received dermatological examination. 102 subjects (0.59%) were found to have psoriasis. After standardization, the prevalence of psoriasis was 0.47%. The prevalence of psoriasis in males and females was 0.54% and 0.44% respectively. 97.06% of the patients had psoriasis vulgaris. 28.43% of the patients reported a family history of psoriasis. 59.80% of patients experienced a negative influence on the quality of life. Conclusions: This population-based and dermatologist-confirmed study showed that the prevalence of psoriasis in China is 0.47%, which is higher than that reported in 1987.

Acne vulgaris is a common skin condition in adolescents. The prevalence of acne is thought to vary between ethnic groups and countries. A large-scale community-based study was performed in six cities in China to determine the prevalence and possible risk factors for acne in the Chinese population. A total of 17,345 inhabitants were included in this study. Of these, 1,399 were found to have acne. No acne was found in subjects under 10 years of age, and only 1.6% in the 10-year-old group had acne. Prevalence then increased rapidly with age, up to 46.8% in the 19-year-old group. After that, it declined gradually with age. Acne was rare in people over 50 years of age. In subjects in their late teens and 20s, acne was more prevalent in males, while in those over 30 years of age it was more prevalent in females. In subjects with acne, 68.4% had mild; 26.0% had moderate and 5.6% had severe acne. In adult acne, persistent acne was much more common (83.3%) than late-onset acne (16.7%). Smoking and drinking were found to be associated with adolescent acne, while no association was found between diet and acne. These results suggest that the prevalence of acne in the Chinese population is lower than that in Caucasian populations, and that adult acne is not uncommon in Chinese subjects.

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Vitiligo is a common skin disease, the prevalence of which varies between races and countries. In China, no population-based study has been reported, although there have been some epidemiological studies on single cities or regions. The objective of this study was to obtain the prevalence and clinical profile of vitiligo in China. The study was conducted in 6 cities. Cluster sampling was used in selecting communities. Residents were visited at home and were asked to complete questionnaires and receive dermatological examinations. A total of 19,974 residents were visited and 17,345 valid questionnaires were obtained. The overall prevalence of vitiligo was 0.56%. Men were affected more than women (0.71% vs. 0.45%, p < 0.01). The prevalence of vitiligo increased with age. The most common type was focal vitiligo (36.1%). A positive family history was found in 9.8% of patients. Thirty-two percent of patients reported a negative impact of vitiligo on their quality of life.

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