July 2 (UPI) -- Most people probably figure the more people in a hospital, the more likely a patient is to get commonly-transferable illnesses, such as Clostridium difficile, or C. diff.
But in a study published in the Journal of Hospital Medicine, a team of researchers from the University of Michigan debunks this assumption.
Hospitals carefully track hospital-acquired infections, or HAIs. But the effort has been missing a key element: how full a hospital was during the hospitalization that the patient acquired the infection. The team decided to look at these factors when analyzing data from California's Office of Statewide Health Planning and Development Patient Discharge Data Set, which tracks hospital discharge records for all licensed general acute care hospitals in California.
The team determined how full a hospital was during the hospitalization of the patient by what percentage of available beds had patients in them, and how thinly stretched the staff were. In doing so, they developed an approach they hope will lead to more uniform tracking of this factor in patient safety.
In the paper, the team shared their first results from using the approach on real-world data related to the digestive tract infection C. diff.
They found that a fuller hospital did not correlate to a higher risk of the infection among patients. Instead, patients were at a higher risk when the hospital was in the middle range of occupancy on the day the patient was admitted.
The study used data from more than 558,000 patient discharges at 327 hospitals across California between 2009 and 2012. It focused on patients who had come to the hospital's emergency room for a heart attack, heart failure or pneumonia.
The researchers found 2,045 patients developed the infection after they reached the hospital.
Lead author Mahshid Abir notes that the new approach takes into account how many beds the hospital actually has open and staffed, rather than how many they're licensed to operate. Other studies in Europe have shown a higher rate of HAIs when hospitals are very full, but those studies used licensed bed counts and did not factor out infections that the patient already had when they got to the hospital.
The team broke occupancy into four levels: low, or 0 to 25 percent; two classes of moderate, 25 percent to 50 percent and 51 percent to 75 percent; and high, or 76 percent to completely full.
Abir said more research must be done to understand the complex relationship between hospital occupancy and outcomes, including analysis of hospital protocols that might be triggered or modified when a hospital is in high or low occupancy.
"The theory that infection rates will go up with occupancy, because of staff cutting corners with steps like handwashing, may seem logical but this model shows it's not as simple as that," says Abir, who leads the Michigan Acute Care Research Unit and is a member of the Michigan Institute for Healthcare Policy and Innovation. "The impacts of emergency department crowding on patient outcomes have been studied extensively, but the effects of occupancy levels on inpatients has been neglected -- despite the fact that a crowded ED is often a function of high inpatient occupancy."
Some hospitals may be implementing operational factors during high occupancy that improve HAIs, she said, and those should be studied.