Cost-Related Underuse of Medicines for Asthma-Opportunities for Improving Adherence.

Background: In asthma, underuse of cost-effective preventive treatments increases morbidity and mortality. The cost of medicines contributes to underuse ("nonadherence"), but the extent to which people with asthma skip or reduce doses or let prescriptions go unfilled when faced with cost pressures is unknown.

Objective: To estimate the extent of cost-related underuse behaviors and associated factors.

Methods: Using previously validated summary indicators, we conducted an online cross-sectional survey of adults and parents of children 5 to 17 years with asthma in Australia (a high-income country) and developed logistic regression models for adults and children with asthma, controlling for key clinical and demographic factors.

Results: The survey was completed by n = 792 adults (mean age, 47 [standard deviation, 17] years, male 47%, concession 60%) and n = 609 parents of children (5-10 years 51%, male 60%, concession 59%) with asthma. Cost-related underuse was reported by 52.9% adults and 34.3% parents, predominantly decreasing or skipping doses to make medicines last longer. Higher odds of cost-related underuse were observed with younger adults (adults: odds ratio [OR]: 1.19; 95% confidence interval [CI]: 1.12, 1.27), males (adults: OR: 1.49; 95% CI: 1.06, 2.08), having concerns about medicines (adults: OR: 3.12; 95% CI: 2.17, 4.35; parents: OR: 2.63; 95% CI: 1.56, 4.55), less comfortable talking to prescribers about cost (parents: OR: 1.22; 95% CI: 1.12, 1.33) or changing medicines (adults: OR: 1.12; 95% CI: 1.03, 1.22), feeling less engaged with prescribers about medicine decisions (parents: OR: 1.11; 95% CI: 1.01, 1.23), and with poorer asthma control (adults, poor control: OR: 1.87; 95% CI: 1.13, 3.09; parents, poor control: OR: 3.87; 95% CI: 1.99, 7.54), and requiring specialist (parents: OR: 1.83; 95% CI: 1.16, 2.87) or urgent health care visits (adults: OR: 1.54; 95% CI: 1.06, 2.23). Income and concession card status were not associated with cost-related underuse.

Conclusions: Adults and parents of children with asthma indicate high rates of cost-related underuse of asthma medicines, even in the context of national medicines subsidies. Urgent targeting of interventions to promote discussion of medicines and costs between doctor and patients, particularly young adult males, is needed.