Medicaid waiver-based housing supports in a safety-net setting: utilization and spending outcomes.

INTRODUCTION: States have expanded Medicaid waiver-based housing support programs, but evidence on outcomes in safety-net settings is limited. METHODS: We evaluated health care utilization and spending associated with Massachusetts Medicaid's Flexible Services Program housing supports (FSP-H), provided to Accountable Care Organization (ACO) members with housing-related needs and qualifying health risks (2021-2024). Within a Boston-based safety-net health system, we linked FSP-H data to claims and electronic health records. Using staggered difference-in-differences, we compared monthly probability of inpatient and emergency department (ED) utilization and per-patient spending in FSP-H recipients (n = 340) vs a contemporaneous comparison group with documented housing-related needs who were FSP-H-ineligible because they were in non-ACO plans (n = 425). We conducted clinical risk-based subgroup analyses. RESULTS: Overall, FSP-H receipt was not associated with significant changes in monthly probability of inpatient utilization (-3.3 percentage points, P = 0.223), ED utilization (-1.5 percentage points, P = 0.569), or monthly spending (-$634, P = 0.053). Massachusetts Medicaid's Flexible Services Program housing supports (FSP-H) was significantly associated with lower monthly inpatient utilization in the substance use disorder and frailty subgroups and with lower monthly spending in the frailty subgroup. CONCLUSION: Findings offer evidence for state Medicaid plans implementing or adapting housing programs.