Health Care Spending And Use Among People Experiencing Unstable Housing In The Era Of Accountable Care Organizations.

Provider organizations are increasingly held accountable for health care spending in vulnerable populations. Longitudinal data on health care spending and use among people experiencing episodes of homelessness could inform the design of alternative payment models. We used Medicaid claims data to analyze spending and use among 402 people who were continuously enrolled in the Boston Health Care for the Homeless Program (BHCHP) from 2013 through 2015, compared to spending and use among 18,638 people who were continuously enrolled in Massachusetts Medicaid with no evidence of experiencing homelessness. The BHCHP population averaged $18,764 per person per year in spending-2.5 times more than spending among the comparison Medicaid population ($7,561). In unadjusted analyses this difference was explained by greater spending in the BHCHP population on outpatient care, including emergency department care, as well as on inpatient care and prescription drugs. After adjustment for covariates and multiple hypothesis testing, the difference was largely driven by outpatient spending. Differences were sensitive to adjustments for risk score, which suggests that housing instability and health risk are meaningfully correlated. This longitudinal analysis improves understanding of health care use and resource needs among people who are homeless or have unstable housing, and it could inform the design of alternative payment models for vulnerable populations.