Decoding Homelessness: Z-Codes and the Recognition of Homelessness as a Comorbid Condition.

There are an estimated 653,100 people across the United States experiencing homelessness. Homelessness is an important social determinant of health associated with increased morbidity and mortality. The prevalence of homelessness among hospitalized patients is substantially higher than the community prevalence, and people experiencing homelessness (PEH) are more likely to be admitted to the hospital and have longer length of stays and higher healthcare costs relative to stably housed patients. The Centers for Medicare and Medicaid Services (CMS) recently introduced an important policy change related to documenting, coding, and billing for homelessness within the Hospital Inpatient Prospective Payment System that all inpatient clinicians, especially those practicing and leading within safety-net systems, should understand. Here, we review the historical purpose and utilization of codes to identify SDOH ("Z-codes"); describe how the recent CMS policy change elevates the importance of homelessness within medical care and impacts reimbursement; analyze the potential risks and benefits of this change to patients, clinicians, and health systems; and assess barriers to implementation. We conclude by calling for health systems to move beyond simply documenting homelessness to meaningfully addressing health inequities in PEH.