Age-stratified comorbidity transitions and interconnected mapping of nine allergic diseases

Background Allergic diseases are highly prevalent chronic inflammatory conditions. They often co-occur because of shared immunological pathways. However, population-level studies covering a broad range of allergic diseases across the lifespan remain limited. The objective of this study was to examine the age-specific trends in allergic disease prevalence, patterns of multimorbidity, and longitudinal interrelationships among nine allergic conditions using a nationwide cohort. Methods We analyzed data from 1,137,861 individuals in the Korean National Health Insurance Service-National Sample Cohort from 2002 to 2019. Nine allergic diseases were tracked: atopic dermatitis, asthma, allergic rhinitis, food allergies, drug allergies, anaphylaxis, allergic conjunctivitis, acute urticaria, and chronic urticaria. We assessed the annual prevalence, concurrent comorbidities, and estimated hazard ratios (HRs) for inter-disease associations using conditional Cox models adjusted for socioeconomic and geographic factors. Network graphs visualized significant associations (HR ≥ 2). Results The prevalence of most allergic diseases increased, including in children and older adults. The proportion of individuals with ≥2 allergic conditions rose from 0.7 % to 4.2 %. Chronic urticaria, atopic dermatitis, and asthma were major precursors of the development of additional allergic diseases. Disease-to-disease associations varied by age, with stronger interconnections observed in adulthood. Predictive modeling suggested increasing future burdens of chronic urticaria and late-onset asthma. Conclusions Allergic diseases exhibit increasing prevalence and multimorbidity across all ages, with strong age-dependent interrelationships. These findings highlight the need for integrated life-course-oriented strategies for allergic disease surveillance and management.