Lower inpatient admission rates at hospitals seemed to correlate to higher rates of unexpected deaths within seven days of discharge from an emergency department, according to a new study published in BMJ.

Led by Ziad Obermeyer, MD, emergency medicine physician and professor at Harvard Medical School, the study could point to problems with care at rural hospitals and whether the motivation to cut down on more expensive inpatient admissions is cutting needed care for patients.

Examining claims data from 2007 to 2012, Obermeyer and his coauthors identified more than 10,000 Medicare patients who died every year within seven days of leaving the ED, without having a life-threatening illness.

“Hospitals in the lowest fifth of rates of inpatient admission from the emergency department had the highest rates of early death (0.27 percent)—3.4 times higher than hospitals in the highest fifth (0.08 percent)—despite the fact that hospitals with low admission rates served healthier populations, as measured by overall seven day mortality among all comers to the emergency department,” Obermeyer and his coauthors wrote.

Mortality declined as a hospital’s admission rate went up. Hospitals in that lowest fifth of admission rates discharged 85 percent of patients, compared to 44 percent in the highest fifth.

Rural hospitals were more prevalent in the lower-admission group (33 percent vs. 17 percent of all hospitals), but didn’t make up a majority.

Whether the deaths were preventable wasn’t addressed by the study, and Obermeyer cautioned these results shouldn’t be taken as evidence of errors by the hospitals.

“Indeed, some of the variation in outcomes we identified could be linked to the geographic and socioeconomic context of emergency care,” he and his coauthors wrote. “First, access to resources varies dramatically across hospitals. For example, to admit patients from the emergency department in hospitals without dedicated internists staffing inpatient beds (hospitalists), emergency physicians must identify willing primary care physicians. These clinicians in turn must take time away from their busy schedules to make rounds on inpatients.”

Still, he argued the results were “not trivial,” and additional testing or monitoring, including inpatient admissions, could have benefitted some patients.