Inhaled corticosteroids (ICS) are the cornerstone of maintenance asthma therapy. However, in spite of this, adherence to ICS remains low. The aim of this systematic literature review was to provide an overview of the current knowledge of adherence to ICS, effects of poor adherence, and means to improve adherence. A total of 19 studies met the inclusion criteria: 9 focusing on the level of adherence, 6 focusing on effects of poor adherence, and 7 focusing on interventions to improve adherence. Three of the studies focused on more than one of these end points. The mean level of adherence to ICS was found to be between 22 and 63%, with improvement up to and after an exacerbation. Poor adherence was associated with youth, being African-American, having mild asthma, < 12 y of formal education, and poor communication with the health-care provider, whereas improved adherence was associated with being prescribed fixed-combination therapy (ICS and long-acting β2 agonists). Good adherence was associated with higher FEV1, a lower percentage of eosinophils in sputum, reduction in hospitalizations, less use of oral corticosteroids, and lower mortality rate. Overall, 24% of exacerbations and 60% of asthma-related hospitalizations could be attributed to poor adherence. Most studies have reported an increase in adherence following focused interventions, followed by an improvement in quality of life, symptoms, FEV1, and oral corticosteroid use. However, 2 studies found no difference in health-care utilization, one observed no effect on symptoms, and one observed more symptoms in subjects in the intervention group compared with the control group. Good adherence to ICS in asthma improves outcome but remains low. Interventions to improve adherence show varying results, with most studies reporting an increase in adherence but unfortunately not necessarily an improvement in outcome. Even following successful interventions, adherence remains low. Further research is needed to explore barriers to adherence and interventions for improvement.
Respiratory Care, 2015, Vol 60, Issue 3, p. 455-468