People who leave hospital against medical advice have an increased risk of being readmitted or even dying within the following six months, a Manitoba study suggests.

When researchers looked at 1,916,104 admissions and discharges of adults in the province from 1990 to 2009, they found 21,417 or 1.1 per cent instances of patients leaving hospital against medical advice.

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For both hospital readmission and death, the elevated rates among patients who left against medical advice started out high and then declined. (iStock)

"Leaving hospital against medical advice can have deleterious consequences for patients, including subsequent readmission to hospital and death," Dr. Allan Garland of the University of Manitoba's faculty of medicine in Winnipeg and his co-authors concluded in Monday's issue of the Canadian Medical Association Journal.

"For both hospital readmission and death, the elevated rates among patients who left against medical advice started out high and then declined, but remained elevated to at least 180 days."

Incomplete treatment of an acute illness was one of the potential reasons for the elevated risk, but researchers said it could also be linked to a patients' characteristics or health behaviours, such as not following medical advice or medication orders, they speculated.

Sixty per cent of readmissions occurred within two weeks.

In the study, people who were of lower socioeconomic status and who had multiple admissions to hospital in the previous five years were among those who were more likely to be readmitted.

Despite the large sample overall, only a small subsample of the discharge data was validated, and some may have been misclassified, the researchers acknowledged. Another limitation was that the severity of illness wasn't measured.

The study was funded by the Manitoba Health Research Council and the Winnipeg Health Sciences Centre Foundation/Department of Research.