Research

Aim 1 • Federal Pharmaceutical Policy

IRA §11406 Insulin Copay Cap in Medicare Advantage

The Question

The Inflation Reduction Act capped insulin copayments at $35/month for Medicare beneficiaries effective January 2023. Does this provision reduce out-of-pocket costs, improve adherence, shift patients toward more efficacious insulin formulations, and reduce acute events in Medicare Advantage populations?

Why It Matters

Insulin affordability is a high-profile policy issue — 1 in 4 patients report cost-related rationing, with 3x higher odds of poor glycemic control. Payers, CMS, and legislators need patient-level evidence on whether the federal cap achieves its intended goals and what the downstream effects are on utilization, formulation switching, and acute events (DKA, HHS, severe hypoglycemia).

Methods

Design: Propensity score matching within Medicare Advantage on baseline out-of-pocket exposure; fallback to within-person + calendar-month fixed effects to control for deductible-phase seasonality.

Data: IQVIA PharMetrics Plus — pharmacy fills, cost-sharing, and utilization patterns in MA populations.

So What?

First patient-level MA estimate accounting for deductible-phase seasonality. First study linking the IRA cap to insulin-type substitution and acute clinical events. Presented at ASHEcon 2025.

Aim 2 • State Pharmaceutical Policy

State Insulin Copay Caps in Commercial and ERISA Populations

The Question

Over 25 states have adopted insulin copay caps since Colorado's January 2020 law. Do these caps reduce out-of-pocket costs, improve adherence, shift insulin formulation mix, and reduce acute events in commercially insured populations — and does ERISA preemption limit the reach of state-level mandates?

Why It Matters

State copay caps are the primary legislative tool for addressing insulin affordability outside Medicare. But ERISA preempts state insurance regulation for self-insured employer plans, potentially leaving a large share of the commercially insured population unaffected. Payers and state legislators need evidence on both the direct effects and the ERISA coverage gap.

Methods

Design: Callaway-Sant'Anna staggered difference-in-differences exploiting variation in state adoption timing. Secondary ERISA preemption triple-DiD comparing fully-insured vs. self-insured plans in cap vs. non-cap states.

Data: IQVIA PharMetrics Plus — commercial fully-insured and self-insured (ERISA) populations across all 50 states.

So What?

First multi-state study linking state insulin copay caps to acute clinical outcomes. Extends existing work with a longer observation window, modern staggered estimator, and clinical endpoints beyond adherence.

Aim 3 • Provider Workforce Policy

APRN and PA Scope-of-Practice Expansions and Diabetes Care Quality

The Question

When states grant Advanced Practice Registered Nurses full practice authority or adopt PA Optimal Team Practice, does diabetes care quality improve — as measured by HEDIS process measures and acute clinical events?

Why It Matters

A projected 139,000+ physician shortfall by 2030 makes scope-of-practice reform one of the most consequential workforce policy levers. Payers evaluating network adequacy, state legislatures weighing SoP bills, and health systems planning workforce strategy all need evidence on whether removing supervisory constraints translates into measurable quality gains.

Methods

Design: Callaway-Sant'Anna staggered difference-in-differences for APRN full practice authority. Event-study descriptive analysis for PA Optimal Team Practice (limited post-period states).

Data: IQVIA PharMetrics Plus — commercial and MA populations. State-level treatment assignment sidesteps the incident-to billing attribution problem.

So What?

First staggered-DiD evaluation linking scope-of-practice reform to combined HEDIS process measures and acute clinical events. Results speak directly to state legislatures, payers, and health systems.

Spatial Epidemiology

Emerging Hotspot Analysis of Diabetic Foot Ulcer Prevalence in Arkansas

Where are diabetic foot ulcers concentrated in Arkansas, what spatial patterns are emerging over time, and what risk factors explain the geographic distribution? DFUs are among the most costly and morbid complications of diabetes, often leading to amputation. This project uses emerging hotspot analysis to identify spatiotemporal trends, combined with explanatory modeling to identify risk factors driving geographic patterns. Findings can guide resource allocation, network design, and targeted intervention programs for payers and public health agencies.