This project seeks to determine whether 3 natural experiments that reduce out-of-pocket costs for diabetes patients improve acute and chronic diabetes complications over the longer term. These natural experiments include: (1) employer adoption of preventive drug lists (PDLs) that make diabetes-related medications $0, (2) state legislation capping patient out-of-pocket costs for insulin, and (3) employer transitions from high- deductible health plans (HDHPs) with substantial financial barriers for most services to generous low- deductible plans. Results could provide evidence about actionable interventions at multiple levels that improve the health of diabetes patients. Studies will leverage a large, national health insurance claims database from 2007-2023 that the research team has refined under previous projects.
The Specific Aims of the project are to: 1. Assess 15-year national trends in (a) diabetes complications and (b) uptake of federal, state, and employer natural experiments of interest. Analyses will assess 2009-2023 trends in acute preventable and chronic microvascular and macrovascular complications, including stratification by key subgroups of interest. Measures related to natural experiment uptake will comprise annual PDL adoption, state-level insulin cost trends, and HDHP to low-deductible plan switches. These analyses will use a longitudinal, calendar time series design with joinpoints, adjusted for changing demographics, socio-economic status, and co-morbidity. 2. Determine if reducing drug out-of-pocket costs improves diabetes complications. Over 4 follow-up years, Aim 2a will examine whether employer switches from health savings account (HSA)-HDHPs with high drug out-of-pocket costs to PDL HSA-HDHPs with $0 preventive drugs reduce acute and chronic diabetes complications.
Aim 2 b will assess these outcomes before and after approximately 10 US states limit insulin cost sharing. Analyses will use a highly rigorous interrupted time series with control series study design and Aim 2a will also apply a segmented survival with control group design. 3. Determine if reducing outpatient and emergency department out-of-pocket costs improves diabetes complications. Analyses will assess if switching from HDHPs with high cost sharing for outpatient and emergency department care to generous low-deductible plans reduces the risk of acute and chronic diabetes complications over 4 follow-up years.
This aim will also use rigorous controlled interrupted time series and segmented survival designs. 4. Examine the long-term impact of reduced out-of-pocket costs on key diabetes subgroups including low-income and high-morbidity members.
Aim 4 will involve stratifying Aims 2 and 3 analyses by characteristics such as income, morbidity, race/ethnicity, and diabetes severity.
This aim will use the same study designs as for Aims 2 and 3 but stratified by the factors of interest.
Over the last decade, increases in diabetes complications such as hyperglycemic coma and heart attack have paralleled increases in out-of-pocket health costs among people aged 18-64. This project will determine whether 3 natural experiments that reduce out-of-pocket costs improve acute and chronic diabetes complications over the longer term. Results could provide evidence about actionable interventions at the Federal, state, and employer level that improve the health of diabetes patients.
