摘要：Objectives. We evaluated the impact of a diagnosis of serious mental illness on use of a primary care provider (vs the emergency department [ED]) as a source of care by people who were chronically homeless. Methods. We used data from 750 chronically homeless adults enrolled in the 11-site Collaborative Initiative to Help End Chronic Homelessness and identified demographic and clinical characteristics independently associated with using a primary care provider rather than an ED. Results. The factor most strongly associated with using the ED as a regular source of medical care was previous-year lack of health insurance. Despite high rates of serious mental illness, neither a diagnosis of serious mental illness nor increased severity of psychiatric symptoms was associated with such use. Conclusions. Findings suggest that people who are chronically homeless and have chronic medical illness would be more likely to access care if they had health insurance. Individual states’ deciding not to expand Medicaid coverage will likely have a tremendous impact on the health outcomes and health care costs associated with this and other vulnerable populations. On a typical night in 2010, approximately 650 000 people were homeless in the United States. 1 Although most people are homeless for only a brief period of time, an estimated 10% have experienced chronic homelessness, defined as continuous homelessness for 1 year or more or at least 4 episodes of homelessness in the past 3 years. 1 Most people experiencing chronic homelessness have chronic health problems and typically have multiple co-occurring conditions. 2 Chronic homelessness has been associated with an increased risk of mortality, with reports of age-adjusted death rates of 2 to 4 times that of the general population 3 and even higher mortality rates from trauma and suicide. 4 Specific chronic medical conditions (HIV, liver disease, and arrhythmia) have been associated with the greatest risk of death. 5 For many chronically homeless individuals, competing demands for shelter, food, and safety supersede the subjective need for primary medical care. 6 This issue is of critical importance, given recent evidence that improved access to primary care reduces mortality 7 and that individuals without a primary care provider (PCP) are less likely to receive recommended preventive care 8 and more likely to have poor health outcomes, such as diabetic ketoacidosis 9 or severe uncontrolled hypertension. 10 Homeless people are less likely than domiciled individuals to use ambulatory care services, 11 relying to a greater extent on emergency department (ED) visits and costly inpatient hospitalizations. 12 The cost of inpatient services for people who are homeless may substantially affect the health care system because almost one quarter of homeless people in the United States report a hospitalization within the previous year. 13 Homeless patients on medical and surgical services remain hospitalized longer than housed patients, resulting in substantial excess costs. 14 Homeless individuals are 3 times more likely to use the ED than are nonhomeless people. 15 A recent large national study of ED use demonstrated that homeless people who seek care in urban EDs come by ambulance, are more likely to lack medical insurance, and have psychiatric and substance use diagnoses than are people who are not homeless. 16 Homeless individuals also appear to use the ED for routine, nonemergency medical needs, 16,17 often for preventable medical problems. 18 Previous research has attempted to determine rates and predictors of medical service use among homeless samples. 11,19–22 The behavioral model for vulnerable populations is a conceptual model for health service use and medical outcomes of people such as those who are chronically homeless. 23 This model predicts the use of health services on the basis of predisposing, enabling, and need factors and identifies the particular challenges vulnerable groups face in obtaining necessary services. This model has been applied to homeless populations, and findings from these studies have suggested that among homeless individuals, drug use increases the risk of medical hospitalization, and psychological distress (self-report of mood over the past 4 weeks) is associated with barriers to obtaining outpatient medical care. 24 The impact of serious psychiatric illness and psychiatric symptom severity on engagement in primary care has not previously been specifically evaluated among chronically homeless individuals. Serious mental illness (schizophrenia or bipolar disorder) may be a more important determinant of underuse of PCPs among homeless people than are logistical barriers such as lack of insurance. Compared with the general population, people who are homeless have substantially higher rates of psychiatric and substance use disorders. 25,26 Evidence has also shown that individuals with serious mental illness underuse primary care even after accounting for their medical need 27 and that severity of psychiatric illness might increase the risk of frequent ED use. 28 In the current study, we identified factors associated with having a regular PCP, as contrasted with relying on ED services as a usual source of care, in a national sample of chronically homeless individuals. In particular, we evaluated the impact of a diagnosis of serious mental illness and psychiatric symptom severity on having a regular source of care.
