Prevalence, Change and Burden of Systemic Corticosteroid Use in Type 2 Inflammation Associated Diseases Over 25 Years - A Nationwide Danish Study

<bold>Background:</bold> Systemic corticosteroid use in type 2 inflammation-associated diseases including asthma, atopic dermatitis, allergic rhinitis, and chronic rhinosinusitis has been associated with adverse outcomes, and corticosteroid-sparing treatments are available.<br /> <bold>Objective:</bold> Assess temporal changes in systemic corticosteroid use and the impact of type 2 inflammation multimorbidity (eg multiple concurrent type 2 inflammation-associated diseases) and specialist assessment on systemic corticosteroid exposure.<br /> <bold>Methods:</bold> Using nationwide databases, all Danish adults with asthma, atopic dermatitis, allergic rhinitis, or chronic rhinosinusitis, based on hospital diagnoses or redeemed prescriptions between 1997 and 2021 were included in an open, serial cross-sectional cohort.<br /> <bold>Results:</bold> Over 25 years, a total of 2,151,209 Danish adults were included. Of those with a single diagnosis (type 2 inflammation monomorbidity),13.9% had asthma, 19.2% allergic rhinitis, 52.9% atopic dermatitis, and 14.0% chronic rhinosinusitis. In terms of type 2 inflammation multimorbidity, 75.1% of included individuals had one, 21.3% two and 3.5% three diagnoses, respectively. Overall, 9.6% of type 2 monomorbid individuals redeemed systemic corticosteroids, with asthma (16.5%) and atopic dermatitis (6.0%) having the highest and lowest prevalence of use. Systemic corticosteroid use peaked in 2006 (10.6%) and was lowest in 2020 (7.2%). Exposure > 5 mg prednisolone/day was constant around 15% overall among users. Type 2 inflammation multimorbidity was associated with increases in systemic corticosteroid use at 9.6%, 16.0% and 20.9% for one, two and three diagnoses, respectively. A median referral delay of 4.1 [8.1] years from first systemic corticosteroid redemption to specialist assessment was seen. Specialist assessment led to a 64.9% reduction in median annual systemic corticosteroid exposure overall.<br /> <bold>Conclusion:</bold> In type 2 inflammation associated diseases, systemic corticosteroid use remains common despite the introduction of corticosteroid-sparing treatments. Timely referrals to specialist assessment could reduce the overall systemic corticosteroid exposure.