Baseline characteristics
The Charlson Comorbidity Index (22) was used as a marker for the overall
comorbidity burden based on International Classification of Diseases
(ICD)-10 codes diagnoses recorded from in- or outpatient hospital
contacts (23) with exclusion of asthma diagnoses (ICD10 J45-J46).
Specific asthma-related comorbidities were chosen from the existing
literature (5, 24-26) and estimated by presence of hospital-given
diagnoses or use of relevant medication dispensed from public pharmacies
in Denmark. Additional details on baseline comorbidities including
specification of applied ICD-10 codes and Anatomical Therapeutic
Chemical (ATC)-codes are available in Online Supplement Table
E2 .
Statistical analyses
Descriptive statistics were presented as number, median and
interquartile range (IQR) for continuous variables, and as frequencies
and percentages for categorical variables. The annual period prevalence
proportion of OCS users was defined as the number of individuals filling
at least one OCS prescription per calendar year per 100 individuals in
the study population, stratified according to OCS-usage groups (high-use
and low-use), and by sex and age categories (18-25 years, 26-35 years,
36-45 years). Lorenz curves (27) for the years 1999, 2009 and 2018 were
computed to assess the skewness of OCS consumptions among the prevalent
OCS users, ranking all users in order by the amount of consumed OCS. The
Gini coefficient, where 0 indicates total equality in consumption among
users and 1 indicates total inequality, was calculated as a single
measure of skewness in consumption of OCS among the users.
Stata Version 16 (StataCorp, College Station, TX, USA) was used in the
analyses.