Comorbidities in an asthma population 8-29 years old: a study from the Norwegian Prescription Database

Abstract

Purpose: To examine occurrence of chronic diseases and antimicrobial treatment in an asthma population 8-29 years old, compared to the general population. Methods: In this cross-sectional study, the asthma population was identified from the general population (retrieved from a census covering the entire Norwegian population) by using filled prescriptions on asthma drugs as a proxy measure of current asthma. The outcome was excess occurrence of specific diseases (comorbidity) among asthmatics, compared to the age-specific general population. Diseases were defined by filled prescriptions with specific diagnostic codes with asthma, compared with the age-specific general population. Diseases were defined by filled prescriptions with specific diagnostic codes (International Classification of Primary Care 2nd edition [ICPC-2] or International Classification of Diseases 10th revision [ICD-10]) during a 1-year period in the Norwegian Prescription Database. Nine chronic diseases were examined: ADHD, epilepsy, migraine, mental illness, cardiovascular disease, diabetes, autoimmune disorders, gastro-oesophageal reflux disease (GORD), allergy. Additionally, antibacterials recommended for respiratory tract infections and antivirals were examined (defined by ATC codes). Standardized Morbidity Ratios (SMR) for each disease was calculated. Results: 59% of the population had at least one of nine chronic diseases examined, compared to 18% in the general population. Few individuals had more than one additional chronic disease (6% of males, 8% of females). SMRs were increased for all diseases except diabetes, implying higher than expected occurrence of the specific diseases in asthmatics. This pattern was observed in both age groups (8-19 and 20-29 years) and genders. Allergy and GORD had highest SMR (range 3.2-4.8) while the other diseases were in the range 1.2-2.5. Conclusions: An excess occurrence of comorbidities was found in the population with asthma. A majority of asthmatics had one additional chronic disease, and few had more than one.