A homeless individual is one who lacks fixed and reliable housing, and approximately 553,000 people fit that description on any given night in the United States. Data suggest a rise in acute hospital use among homeless individuals for mental illness and substance use disorder. 

A new retrospective cohort study led by investigators from Beth Israel Deaconess Medical Center (BIDMC) and Brigham and Women's Hospital examines patterns, causes, and outcomes of acute hospitalizations between 2007 and 2013 for homeless individuals and non-homeless control groups in three populous and diverse U.S. states: Florida, California, and Massachusetts.

The rate of hospitalizations

"The homeless population is aging, and the rate of hospitalizations for homeless individuals is increasing," said lead author Rishi Wadhera, MD, an investigator in the Smith Center for Outcomes Research in Cardiology at BIDMC.

"Although there has been a recent push to establish better policy and public health measures to improve the health of homeless adults, few studies have examined the patterns and causes of hospitalizations in this population," said Wadhera.

"We found that hospitalizations among homeless adults tend to be for a very different set of conditions than non-homeless adults, even after accounting for differences in demographics," said Wadhera.

To examine these trends, hospital discharge data was acquired from Massachusetts and Florida between 2001 and 2013 and from California between 2007 and 2011. This information came from the State Inpatient Databases (SID) of the Healthcare Cost and Utilization Project, created by the Agency for Healthcare Research and Quality.

This dataset includes information such as homeless status, billing, demographics, and diagnoses. Hospitalization costs were determined by applying American Hospital Association cost-to-charge ratios to the total hospital charges provided in the SID.

Overall, the researchers analyzed more than 185,000 hospitalizations for homeless individuals and 32 million hospitalizations for non-homeless individuals. Between 2007 and 2013 (2011 for Calif.), acute hospitalizations for homeless individuals increased in all three states.

Massachusetts experienced an increase from 294 to 420 per 1,000 homeless individuals, Florida increased from 161 to 240/1,000, and California grew from 133 to 164/1,000. Homeless adults were more often white (62%), male (76.1%), around 46 years old, and either uninsured (41.9%) or insured by Medicaid (31.7%).

The researchers found that reasons for hospitalization among the two groups differed starkly. More than 50% of hospitalizations among homeless individuals were related to mental illness and substance use disorder, while these conditions explained less than 20% of hospitalizations among demographically comparable non-homeless individuals.

Homeless adults also had a longer mean length of stay (6.5 vs. 5.9 days). However, homeless individuals had lower in-hospital mortality rates (0.9% vs. 1.2%) and lower mean costs per day ($1,535 vs. $1,834) than the comparable non-homeless control group.

"Some states, such as Massachusetts, have expanded Medicaid eligibility, which has increased rates of insurance among homeless individuals and improved access to care; this could have led to greater use of hospital services," said Wadhera, who is also a cardiology fellow in the Cardiovascular Division at Brigham and Women's Hospital.

"The increase in hospitalizations could also re flect more concerning trends. The opioid epidemic has disproportionately impacted the homeless population, and a repercussion of this may be an increase in acute hospitalizations," said Wadhera.

"It is also possible that these patterns suggest inadequate outpatient care for homeless individuals, and that we need to do a better job of providing more consistent, reliable outpatient care to this population," said Wadhera.

"There is an urgent need to reduce financial and nonfinancial barriers to the use of ambulatory care, for behavioral health services, in particular, to improve long-term management of physical and mental illness for homeless individuals," said senior author Karen Joynt Maddox, MD, MPH, of Washington University in St. Louis. "We need better longitudinal data and further studies to understand how Medicaid expansion and other policy initiatives affect the health of this highly vulnerable population."