Atopic dermatitis is associated with abnormal stool form: a population-based cross-sectional study in college students

Background Atopic dermatitis (AD) is a chronic inflammatory skin disorder. Bristol Stool Form Scale (BSFS) is a widely used stool scoring method that could indirectly reflect intestinal function. Objectives To evaluate the associations of AD with BSFS. Methods This was a population-based cross-sectional study of freshmen in five universities of China. AD diagnosis was performed by dermatologists according to the guideline from the American Academy of Dermatology. BSFS and covariates were collected through an online questionnaire survey. Chronic itch scores were assessed by the numeric rating scales and grouped into quartiles (Q). Mixed logistic regression models were used. Subgroup analysis was conducted by covariates. P value < 0.05 was considered statistically significant. Results The prevalence of hard stools and loose stools were 8.9% and 7.6%, respectively (20,049 participants). After adjusting covariates, AD was significantly associated with hard stools (OR = 1.38, P < 0.001) and loose stools (OR = 1.24, P = 0.037). In subgroup analysis of hard stool, a stronger effect was observed in intake of milk (> 3 days/week), yogurt (> 3 days/week), pork (< 1 day/week), and higher itch scores (Q4). Conclusion This study found the relationship between AD and abnormal stool forms, and the association with hard stools might be modified by dietary factor.