Nearly one in five adult hospital patients are discharged with at least one unstable vital sign, a new study from University of Texas researchers has found.

Those instabilities have become a growing concern over the past three decades as hospital stays have shortened dramatically, researchers said. Of the 32,835 patients included in the study, almost 20% had one of more vital sign “abnormality” upon discharge. Elevated heart rate was the most common, affecting 10% of all patients.

Those unstable vitals, which also include abnormalities with temperature, blood pressure, respiratory rate and oxygen saturation, increase patients’ risk of hospital readmission and death, researchers noted. Thirteen percent of the patients were readmitted or died in the 30 days following hospital discharge.

Post-acute care facilities were found to be a “frequent” post-discharge care setting for those with unstable vital signs. Those patients were still found to have high rates of readmission and death, leading researchers to suggest than another post-discharge setting may have been better “for a significant subset of these individuals,” researchers said.

Patients with three or more vital sign instabilities had nearly four times the risk of dying once they were discharged.

“At a time when people are developing complicated, black box computerized algorithms to identify patients at high risk of readmission, our study highlights that the stability of vital signs, something doctors review with their own eyes every day, is a simple, clinically objective means of assessing readiness and safety for discharge,” wrote senior study author Ethan Halm, M.D., MPH. “There’s a good reason we call them vital signs.”

Halm’s team recommended that patients with one instability be discharged “with caution,” while those with more stay in the hospital for treatment. The researchers also advocated for close post-discharge follow-up and improved patient education about their vital signs.

The study was published Monday in the Journal of General Internal Medicine.