Association between severity of different body regions and inadequate control of atopic dermatitis: results from a cross-sectional and longitudinal study.

Background: The Atopic Dermatitis Control Tool (ADCT) serves as a key metric for assessing atopic dermatitis (AD) management. However, the relationship between eczema severity in different body regions and inadequate control in AD patients has not been extensively researched. This study aimed to examine this association in both children and adults with AD and to further explore temporality and treatment effects through longitudinal follow-up. Methods: A cross-sectional questionnaire survey was conducted on pediatric and adult patients with AD in Guangzhou, China. The questionnaires were completed by the AD patients attending the Department of Dermatology at Guangdong Provincial Hospital of Chinese Medicine between March, 2024 and December, 2025. Additionally, a longitudinal sub-cohort of 96 AD patients with 24-week follow-up data was retrospectively analyzed. Results: A total of 713 AD patients completed the survey, including 175 children (aged 12-17 years old) and 538 adults. In the pediatric group, the severity of the head and neck and lower limbs was independently associated with inadequate disease control. In the adult group, the severity of the lower limbs was independently associated with poor disease control. In the longitudinal cohort, improvements in disease severity of the head and neck and lower limbs from baseline to week 24 were independently associated with ADCT-defined clinical improvement. Conclusion: The AD control status exhibits age-specific regional associations. Longitudinal data further demonstrate that reductions in disease severity in the head and neck and lower limbs were independently associated with clinical improvement. These findings are exploratory and require prospective validation before they can inform treatment prioritization.