Habitual Scratching in Atopic Dermatitis and Its Association with Disease Severity: Findings from Japanese Health Insurance Claims and App-Based Data.

INTRODUCTION

In atopic dermatitis (AD), scratching sustains inflammation and impairs the skin barrier. Beyond scratching driven by itch, affected individuals may engage in habitual scratching, defined as repetitive, unconscious scratching that occurs without itch. The extent and clinical significance of habitual scratching in Japanese patients remain unclear. This study aimed to assess the frequency of habitual scratching and its association with AD severity in the Japanese population.

METHODS

This cross-sectional study was conducted in Japan using data from anonymized health insurance claims and a nationwide app-based questionnaire administered in October 2022. Included individuals were adults (aged 19-74 years) and children (aged ≤ 18 years) with a self-reported diagnosis of AD and either symptoms or treatment within the previous 6 months. Habitual scratching was assessed using two yes/no questions. Disease severity was measured using the Patient-Oriented Eczema Measure (POEM), and associations were tested using the Cochran-Armitage trend test.

RESULTS

A total of 1507 adults and 525 children were included. Among adults, 44.5% reported scratching without feeling itchy, and 30.0% reported only noticing scratching when it was pointed out; among children, these proportions were 57.5% and 53.3%, respectively. The proportion of patients exhibiting both behaviors increased significantly with POEM severity. For scratching without itch, rates ranged from 35.1% to 62.9% in adults and from 44.5% to 82.6% in children (p < 0.001 for both). For unnoticed scratching, rates ranged from 19.0% to 50.3% in adults and from 41.2% to 69.6% in children (p < 0.001 for both).

CONCLUSIONS

Habitual scratching was commonly reported across all severity levels of AD in Japan and was associated with greater disease severity. These findings highlight the importance of recognizing/noticing and actively managing unconscious scratching behaviors as part of comprehensive AD care.