Atopic dermatitis: Correlation of distinct risk factors with age of onset in adulthood compared to childhood

Background: Atopic dermatitis (AD) has long been regarded as a primarily pediatric disease. However, there is growing evidence for a high rate of adult-onset AD. We aimed to characterize factors associated with adult-onset versus childhood-onset AD and controls. Methods: We analyzed cross-sectional data of the CK-CARE-ProRaD cohorts Bonn, Augsburg, Davos, Zürich of 736 adult patients stratified by age of AD onset (childhood-onset <18 years: 76.4% (subsets: 0 to 2; ≥2 to 6; ≥7 to 11; ≥12 to 18); adult-onset ≥18 years: 23.6% (subsets: ≥18 to 40; ≥41 to 60; ≥61) and 167 controls (91 atopic, 76 non-atopic)). Results: We identified active smoking to be associated with adult-onset AD versus controls (adjusted Odds Ratio (aOR) = 5.54 [95% Confidence Interval: 1.06–29.01] vs. controls^non-atopic, aOR = 4.03 [1.20–13.45] vs. controls^atopic). Conjunctivitis showed a negative association versus controls^atopic (aOR = 0.36 [0.14–0.91]). Food allergy (aOR = 2.93 [1.44–5.96]), maternal food allergy (aOR = 9.43 [1.10–80.95]), palmar hyperlinearity (aOR = 2.11 [1.05–4.25]), and academic background (aOR = 2.14 [1.00–4.54]) increased the odds of childhood-onset AD versus controls^atopic. Shared AD-associated factors were maternal AD (4-34x), increased IgE (2-20x), atopic stigmata (2-3x) with varying effect sizes depending on AD onset and control group. Patients with adult-compared to childhood-onset had doubled odds of allergic rhinitis (aOR = 2.15 [1.12–4.13]), but reduced odds to feature multiple (3–4) atopic comorbidities (aOR = 0.34 [0.14–0.84]). Adult-onset AD, particularly onset ≥61 years, grouped mainly in clusters with low contributions of personal and familial atopy and high frequencies of physical inactivity, childhood-onset AD, particularly infant-onset, mainly in “high-atopic”-clusters. Conclusions: The identified associated factors suggest partly varying endo- and exogeneous mechanisms underlying adult-onset versus childhood-onset AD. Our findings might contribute to better assessment of the individual risk to develop AD throughout life and encourage prevention by non-smoking and physical activity as modifiable lifestyle factors.