Atopic dermatitis/eczema phenotypes and their association with food allergy: a nationwide birth cohort study in Japan.

Atopic dermatitis (AD) is a heterogeneous disease often preceding food allergy (FA). However, it remains unclear how different developmental trajectories of AD/eczema influence the risk of FA. This study aimed to characterize longitudinal AD/eczema phenotypes from infancy to early adolescence and evaluate their specific associations with FA risk. We analyzed data from the Longitudinal Survey of Newborns in the 21st Century in Japan, including 23,767 participants followed from age 0.5 to 12 years. Distinct AD/eczema phenotypes were identified using group-based trajectory modeling derived from healthcare visit histories. Multivariable logistic regression examined the association between AD/eczema phenotypes and cumulative FA healthcare visit history, adjusting for sociodemographic factors and asthma comorbidity. Five AD/eczema phenotypes were identified: "Early-onset transient" (6.4%), "Early-onset persistent" (23.2%), "Toddler-onset persistent" (17.3%), "Late-onset" (2.1%), and "No/minimal symptoms" (51.0%). Compared with the "No/minimal symptoms" group, all AD/eczema phenotypes were associated with increased FA risk. The "Early-onset transient" (adjusted odds ratio [aOR], 2.33; 95% CI, 1.98-2.74) and "Early-onset persistent" (aOR, 2.33; 95% CI, 2.10-2.59) groups showed the strongest associations. The "Late-onset" phenotype was also associated with increased risk (aOR, 1.42; 95% CI, 1.04-1.93), with elevated risk observed in early childhood preceding the peak of overt skin symptoms.

conclusionDistinct developmental trajectories of AD/eczema are differentially associated with FA risk. While early-onset phenotypes confer the highest risk, the elevated risk in "Late-onset" trajectories before peak symptoms suggests shared underlying susceptibility or subclinical pathology. Monitoring FA development is important across all clinical trajectories of AD/eczema. WHAT IS KNOWN: • Atopic dermatitis (AD) is a primary precursor for the atopic march, but how different longitudinal trajectories influence food allergy (FA) risk remains unclear. • Early-onset persistent AD is considered to pose the highest risk for FA. WHAT IS NEW: • Early-onset transient AD/eczema carries a high FA risk comparable to persistent cases, indicating that timing of onset is more critical than disease duration for FA development. • Late-onset AD/eczema trajectories show elevated FA risk in early childhood preceding peak skin symptoms, suggesting shared underlying susceptibility or subclinical pathology.