Factors associated with low adherence to inhaled therapy in patients with chronic respiratory diseases: a cross-sectional study.

Background: Because of their high prevalence, chronic respiratory diseases, like asthma and chronic obstructive pulmonary disease, represent main public health problems. They are mainly treated through inhaled therapy. There is low adherence to such therapy, resulting in poor control of chronic respiratory diseases. However, more research is needed on the association of several factors with low adherence. The purpose of this study was to estimate the association of age, sex, type of drug, and frequency of administration with low adherence to inhaled therapy. In order to do this, we performed a cross-sectional study.

Methods: We selected all patients treated with long-acting anticholinergics (LAMA), long-acting β2-adrenergics (LABA), LAMA/LABA, or inhaled corticosteroid (ICS)/LABA in the Health Area of Lleida on 16 March 2017. For each treatment, we determined the percentage of patients showing low adherence to therapy (less than 50%), calculated as drug boxes collected from the pharmacy with respect to the prescribed ones. Then, we analysed the association of age, sex, type of drug, and frequency of administration, with low adherence to therapy through a multivariate linear model.

Results: 11,128 people had electronic prescriptions for one of the inhaled therapy; of them, 24.6% (2,741) showed low adherence. The highest percentage of people with low adherence was found among young patients and women. Women 25-34 years of age included the highest percentage of patients with low adherence. As for drugs, the highest percentage of patients with low adherence was found among the ones treated with LABA and ICS/LABA. Finally, a higher percentage of patients with an administration frequency of 12 h presented low adherence, in comparison with patients treated every 24 h, in general and in the LABA and ICS/LABA groups.

Conclusions: The differences that we observed in adherence to inhaled therapy according to the different factors analysed should be considered when managing chronic respiratory diseases and their impact on patients' clinical burden, quality of life, and costs for the health system.