The REG Adherence Working Group has recently published a paper in JACI in practice that investigates the relationship between ICS implementation and asthma-related outcomes, considering bidirectionality and temporal sequence.
Primary care records of 10,472 asthma patients from the Optimum Patient Care Research Database (www.opcrd.co.uk) were used. For each prescription interval (period between two successive prescriptions) in the 2-year outcome period ICS implementation (percentage of days covered) and Risk Domain Asthma Control (RDAC; no moderate or severe exacerbations) were estimated.
ICS implementation in the preceding prescription interval did not predict RDAC, but that ICS implementation was weakly positively associated with simultaneous RDAC. Being male, non-current smoker, without a COPD diagnosis and having <4 comorbidities significantly increased odds of RDAC. Asthma-related antibiotic prescriptions and asthma-related outpatient visits in the same interval, and SABA overuse in the preceding and same interval predicted lower ICS implementation.
The lack of an association between ICS implementation and RDAC in consecutive intervals may suggest that patients may adapt their ICS use to meet their current needs without this impacting their later RDAC.
https://www.sciencedirect.com/science/article/abs/pii/S2213219819307809