Utilization and Spending With Preventive Drug Lists for Asthma Medications in High-Deductible Health Plans.

Importance: High-deductible health plans with health savings accounts (HDHP-HSAs) incentivize patients to use less health care, including necessary care. Preventive drug lists (PDLs) exempt high-value medications from the deductible, reducing out-of-pocket cost sharing; the associations of PDLs with health outcomes among patients with asthma is unknown. Objective: To evaluate the associations of a PDL for asthma medications on utilization, adverse outcomes, and patient spending for HDHP-HSA enrollees with asthma. Design, Setting, and Participants: This case-control study used matched groups of patients with asthma before and after an insurance design change using a national commercial health insurance claims data set from 2004-2017. Participants included patients aged 4 to 64 years enrolled for 1 year in an HDHP-HSA without a PDL in which asthma medications were subject to the deductible who then transitioned to an HDHP-HSA with a PDL that included asthma medications; these patients were compared with a matched weighted sample of patients with 2 years of continuous enrollment in an HDHP-HSA without a PDL. Models controlled for patient demographics and asthma severity and were stratified by neighborhood income. Analyses were conducted from October 2020 to June 2023. Exposures: Employer-mandated addition of a PDL that included asthma medications to an existing HDHP-HSA. Main Outcomes and Measures: Outcomes of interest were utilization of asthma medications on the PDL (controllers and albuterol), asthma exacerbations (oral steroid bursts and asthma-related emergency department use), and out-of-pocket spending (all and asthma-specific). Results: A total of 12 174 participants (mean [SD] age, 36.9 [16.9] years; 6848 [56.25%] female) were included in analyses. Compared with no PDL, PDLs were associated with increased rates of 30-day fills per enrollee for any controller medication (change, 0.10 [95% CI, 0.03 to 0.17] fills per enrollee; 12.9% increase) and for combination inhaled corticosteroid long-acting β2-agonist (ICS-LABA) medications (change, 0.06 [95% CI, 0.01 to 0.10] fills per enrollee; 25.4% increase), and increased proportion of days covered with ICS-LABA (6.0% [0.7% to 11.3%] of days; 15.6% increase). Gaining a PDL was associated with decreased out-of-pocket spending on asthma care (change, -$34 [95% CI, -$47 to -$21] per enrollee; 28.4% difference), but there was no significant change in asthma exacerbations and no difference in results by income. Conclusions and Relevance: In this case-control study, reducing cost-sharing for asthma medications through a PDL was associated with increased adherence to controller medications, notably ICS-LABA medications used by patients with more severe asthma, but was not associated with improved clinical outcomes. These findings suggest that PDLs are a potential strategy to improve access and affordability of asthma care for patients in HDHP-HSAs.