Prevalence of atopic dermatitis in Japanese adults

BACKGROUND: Adult atopic dermatitis (AD) in Japan has become a significant social problem, with as many as one-third of adult patients with severe AD absenting themselves from work or classes due to aggravation of the disease. Reports of such patients have become increasingly common in recent years. Despite the pressing need for epidemiological studies to clarify the prevalence and distribution of AD and to determine its aetiology, no previous research has been carried out on the prevalence of AD within the adult population in Japan. OBJECTIVES: To clarify the prevalence of adult AD in Japan, using the U.K. Working Party's diagnostic criteria. METHODS: The subjects of this study were mostly government officials or their family members visiting the Medical Center of Health Science, Toranomon Hospital in Tokyo for annual health check-ups in the period from September 1997 to August 1998. Questionnaires completed by 10 762 persons (8076 men and 2686 women) aged 30 years or above were analysed. The questionnaire consisted of 14 questions on allergic disease. The U.K. Working Party's diagnostic criteria were used after translation into Japanese. Three types of prevalence were used as indicators of prevalence: point, 1-year and lifetime prevalence. RESULTS: The point prevalence, 1-year prevalence and lifetime prevalence of AD in Japanese adults were 2.9%, 3.0% and 3.3%, respectively. No significant statistical differences were observed between the sexes or among age groups within each sex. The survey indicated that 88.6% of those who had ever had AD were currently affected by active AD, while 93.4% of those who had had at least one episode of AD in the past had experienced an episode over the previous year. CONCLUSIONS: This study gives the first indication of the prevalence of adult AD among the Japanese, based on the U.K. criteria. Both the internal and external validity of this study are believed to be high; it would be safe to conclude that the 1-year prevalence of AD in Japanese adult populations living in urban areas is 3.0%.