Age-related differences in adherence to inhaled corticosteroids among adult patients with asthma: a national cohort study in South Korea

Understanding age-related differences in adherence to inhaled corticosteroids (ICSs) is crucial to optimize asthma management. To explore differences in adherence levels among different age groups of adult patients with asthma in South Korea from January 2016 to December 2020. We performed a population-based cohort study using data from South Korea’s National Health Insurance Service, including individuals aged 18 to 79 who began using ICS between 2016 and 2020. Adults with asthma were categorized into three age groups: young adults (18–39 years of age), middle-aged adults (40–59 years of age), and older adults (60–79 years of age). The primary outcomes were medication adherence, indicated by the proportion of days covered (PDC), and persistence. Additionally, asthma outcomes, including the risk of asthma exacerbation and pneumonia, were analyzed. Among the 15,367 included patients, 4,237 were young adults, 6,132 were middle-aged adults, and 4,998 were older adults. Older adults had a significantly higher PDC (0.56 ± 0.20) than middle-aged (0.53 ± 0.20) and young adults (0.52 ± 0.20; P < .001). Additionally, older adults had a 29.4% lower risk of discontinuation compared with young adults (adjusted hazard ratio aHR, 0.706; 95% confidence interval CI, 0.667–0.747; P < .001) and a 13.4% lower risk compared with middle-aged adults (aHR, 0.866; 95% CI, 0.821–0.913; P < .001). Despite higher medication adherence, older adults experienced a higher risk of severe asthma exacerbations (aHR, 1.848; 95% CI, 1.568–2.178; P < .001) than young adults. Older adults demonstrated better adherence to ICS-containing inhalers but also had higher risks of severe exacerbations and pneumonia, highlighting the necessity for age-specific management strategies.