Prevalence, Severity, and Clinical Course of Atopic Dermatitis in Japan: A Web-Based Questionnaire Survey.

Atopic dermatitis is a chronic inflammatory skin disease that commonly begins in childhood but exhibits heterogeneous long-term clinical courses. We conducted a cross-sectional questionnaire survey among dermatologists to evaluate age-specific prevalence, remission proportion, severity, and disease course of atopic dermatitis in Japan. Data from 7777 individuals, including respondents and their family members, were analyzed. The prevalence of atopic dermatitis peaked at 5-9 years of age and gradually declined with age, although a substantial proportion of affected individuals remained in adulthood. Overall, prevalence was higher in males than in females, with a significant difference observed in the youngest age group. The proportion of individuals with a remitted disease course increased with age and plateaued after approximately 40 years. Remission proportions were higher in females than in males overall, although age-specific differences were not consistently significant. Most cases were almost clear or mild; however, moderate-to-severe disease was observed in a subset of individuals across age groups, without marked sex differences. Regarding disease course, remission after childhood onset was the most common pattern, followed by relapse, persistence, and adult-onset disease. Remission-type courses were more frequent in females, whereas persistent and relapsing patterns were more common in males. These findings suggest that atopic dermatitis persists into adulthood in a substantial proportion of individuals and follows diverse clinical trajectories across the lifespan.