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 ␤ 2 agonists). Good adherence was associated with higher FEV 1 , 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 asthmarelated 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, FEV 1 , 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.

Background and objectiveIn recent years, the so-called asthma–chronic obstructive pulmonary disease (COPD) overlap syndrome (ACOS) has received much attention, not least because elderly individuals may present characteristics suggesting a diagnosis of both asthma and COPD. At present, ACOS is described clinically as persistent airflow limitation combined with features of both asthma and COPD. The aim of this paper is, therefore, to review the currently available literature focusing on symptoms and clinical characteristics of patients regarded as having ACOS.MethodsBased on the preferred reporting items for systematic reviews and meta-analyses (PRISMA) guidelines, a systematic literature review was performed.ResultsA total of 11 studies met the inclusion criteria for the present review. All studies dealing with dyspnea (self-reported or assessed by the Medical Research Council dyspnea scale) reported more dyspnea among patients classified as having ACOS compared to the COPD and asthma groups. In line with this, ACOS patients have more concomitant wheezing and seem to have more cough and sputum production. Compared to COPD-only patients, the ACOS patients were found to have lower FEV1% predicted and FEV1/FVC ratio in spite of lower mean life-time tobacco exposure. Furthermore, studies have revealed that ACOS patients seem to have not only more frequent but also more severe exacerbations. Comorbidity, not least diabetes, has also been reported in a few studies, with a higher prevalence among ACOS patients. However, it should be acknowledged that only a limited number of studies have addressed the various comorbidities in patients with ACOS.ConclusionThe available studies indicate that ACOS patients may have more symptoms and a higher exacerbation rate than patients with asthma and COPD only, and by that, probably a higher overall respiratory-related morbidity. Similar to patients with COPD, ACOS patients seem to have a high occurrence of comorbidity, including diabetes. Further research into the ACOS, not least from well-defined prospective studies, is clearly needed.

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