Reduced Cost-sharing for Preventive Drugs Preferentially Benefits Low-income Patients With Diabetes in High Deductible Health Plans With Health Savings Accounts.

Background: High deductible health plans linked to Health Savings Accounts (HSA-HDHPs) must include all care under the deductible except for select preventive services. Some employers and insurers have adopted Preventive Drug Lists (PDLs) that exempt specific classes of medications from deductibles.

Objective: The objective of this study was to examine the association between shifts to PDL coverage and medication utilization among patients with diabetes in HSA-HDHPs.

Research Design: A natural experiment comparing pre-post changes in monthly and annual outcomes in matched study groups.

Subjects: The intervention group included 1744 commercially-insured HSA-HDHP patients with diabetes age 12-64 years switched by employers to PDL coverage; the control group included 3349 propensity-matched HSA-HDHP patients whose employers offered no PDL.

Measures: Outcomes were out-of-pocket (OOP) costs for medications and the number of pharmacy fills converted to 30-day equivalents.

Results: Transition to the PDL was associated with a relative pre-post decrease of $612 (-35%, P<0.001) per member OOP medication expenditures; OOP reductions were higher for key classes of antidiabetic and cardiovascular medicines listed on the PDL; the policy did not affect unlisted classes. The PDL group experienced relative increases in medication use of 6.0 30-day fills per person during the year (+11.2%, P<0.001); the increase was more than twice as large for lower-income (+6.6 fills, +12.6%, P<0.001) than higher-income (+3.0 fills, +5.1%, P=0.024) patients.

Conclusion: Transition to a PDL which covers important classes of medication to manage diabetes and cardiovascular conditions is associated with substantial annual OOP cost savings for patients with diabetes and increased utilization of important classes of medications, especially for lower-income patients.