Medication in Adult-Onset Asthma: Focus on adherence, inhaled corticosteroids, and short-acting β2-agonists

Asthma is a chronic inflammatory disease affecting over 300 million people worldwide, presenting an enormous burden for society and individuals. As asthma rarely remits, especially in patients with adult-onset asthma, treating asthma involves long-term medication. Unfortunately, previous studies have shown that patients’ adherence to treatment is suboptimal, with adherence rates usually being under 50%. However, studies evaluating adherence to asthma controller medication (inhaled corticosteroids) have typically been short-term follow-ups, and little is known about the variation of medication adherence between and within persons in long-term treatment.

The present study aims to evaluate medication use, adherence to controller medication (inhaled corticosteroids), and its variability in long-term treatment in real- life new-onset adult asthma patients. Further aims were to assess the factors associated with non-controlled asthma and investigate the relationship between patients’ controller and reliever medications.

The present study examined patients in the Seinäjoki Adult Asthma Study (SAAS), a 12-year single-center follow-up study of patients with new-onset adult asthma (n=203). Patients’ asthma-related visits and prescribed controller medication over the study were collected from medical records. The information on dispensed inhaled corticosteroids (ICS) (controllers) and short-acting β2-agonists (SABA) (relievers) was obtained from the Finnish Social Insurance Institution, which records all reimbursed asthma medication purchases from any Finnish pharmacy. By comparing the prescribed doses to dispensed doses ([µg dispensed/µg prescribed]×100), assessing individual real-life ICS medication adherence annually and cumulatively during a 12-year follow-up period was possible. All doses of dispensed SABAs during the 12-year follow-up were counted; the sum was divided by 150 to express SABA use as standard canisters of 150 doses. High SABA use was defined as ≥36 canisters in 12 years, corresponding to an average of ≥3 dispensed canisters/year. Asthma control was evaluated after 12 years of treatment according to the Global Initiative for Asthma 2010 guideline.

The average 12-year adherence to ICS medication was relatively high (69%) in patients with new-onset adult asthma. When patients were grouped based on their level of asthma control, higher ICS doses were prescribed to patients with uncontrolled asthma compared to patients with controlled and partially controlled asthma. The mean 12-year adherence to ICS was higher in patients with non- controlled asthma (76%) than in patients with controlled asthma (63%). Among patients with non-controlled asthma, those with a lower 12-year adherence (<80%) had more rapid decline in forced expiratory volume in 1 s than those with better adherence (≥80%). High SABA use was infrequent in patients with confirmed adult- onset asthma, as only 10% of the patients were classified as high SABA users during the study. Obesity (body mass index [BMI] ≥30) and high Airways Questionnaire 20 symptom scores at baseline predicted high long-term SABA use.

The current study’s results show that patients with adult-onset asthma have moderate adherence to long-term ICS treatment, and high use of reliever medication is infrequent. Lower adherence (<80%) was associated with more rapid lung function decline in the long term, underscoring the importance of each patient’s adherence to treatment. High adherence to high-dose ICS treatment was insufficient to improve asthma control among non-controlled patients. A possible explanation could be the lower degree of Type 2 inflammation, resulting in reduced efficacy of ICS. Therefore, tapering the ICS doses should be considered, and focusing on more individualized treatment approaches, pharmacological and non-pharmacological, must be emphasized in adult-onset asthma patients.