Distinct epidemiological patterns of allergic disease comorbidity across elementary school grades in Taiwan

Background: Allergic diseases have increasingly co-occurred in children, but grade-specific patterns of multimorbidity and their implications for school-based screening remain unclear. Methods: In this cross-sectional study of 2380 Taiwanese elementary school children (1215 first-graders and 1165 sixth-graders), ISAAC-based questionnaires assessed asthma, allergic rhinitis, atopic dermatitis, and sociodemographic factors. We quantified grade-specific prevalence, recent symptom burden, and allergic multimorbidity burden (0–3 concurrent conditions), and evaluated determinants using multinomial logistic regression. Results: Lifetime prevalence of each allergic condition was similar between grades, yet disease clustering differed. First-graders, particularly boys, had more wheeze in the past 12 months, a lower proportion of disease-free children, and higher 2–3 disease multimorbidity than sixth-graders. Male sex showed stepwise higher risks with increasing multimorbidity, maternal graduate education was independently associated with triple-disease multimorbidity, and overweight status was inversely associated with rhinitis symptoms. Conclusions: Allergic multimorbidity, rather than single‑disease prevalence, captures a concentrated burden in first‑grade boys and reveals sociodemographic gradients in diagnosis. These findings support risk‑stratified, grade‑ and sex‑specific allergy screening and management in early elementary school. Impact: Allergic multimorbidity, rather than single-disease prevalence, better identifies pediatric allergic disease burden across elementary school grades. This study shows that first-grade boys carry the highest burden of recent wheeze and multi-disease allergic comorbidity, despite similar cumulative prevalence across grades. It adds evidence that male sex and maternal graduate education are independently associated with more complex multimorbidity patterns in schoolchildren. These findings support risk-stratified, grade- and sex-specific school-based screening and early intervention during the early elementary years.