After-hours medical clinics can help reduce the demand on overcrowded hospital emergency wards, a new University of Alberta study finds.

Previous studies on how such clinics affect the number of patients who head to ERs have been inconclusive. But that may be because the clinics that were studied were too small to offset much of the demand on nearby hospital emergency rooms.

This study looked at the relatively small town of Leduc, Alta., a town of 20,000 near Edmonton with a single hospital.

Doctors at the Leduc Hospital had noted they were increasingly seeing patients in their ER who could have been better served in a doctor's office.

So with the town planning to open a new after-hours clinic that would be open in the evening from 6 p.m. to 10 p.m. four days a week, David Jones, a graduate student at the University of Alberta's School of Public Health, decided to see how the clinic would affect the hospital.

For 14 months prior to the opening of an after-hours clinic, he and a small team counted how many semi-urgent and non-urgent cases went to the emergency room and then how many went for the 14 months after the clinic opened.

Semi-urgent cases include such minor traumas as burns, or abdominal pain, while non-urgent patients have such things as nasal congestion or chronic low back pain.

Such cases can usually be treated in a doctor's office and have long been known to contribute to emergency department overcrowding.

The researchers found there was a 40 per cent reduction in such patients using the emergency department after the clinic opened.

The after-hours clinic saw an average of 261 patient visits per month after it opened. At the same time, there were 49 fewer semi-urgent patient visits per month to the Leduc ER during the clinic's operating hours. And overall, there were about 37 fewer total patient visits to the ER per month.

"This study provides further evidence that offering these services can positively impact emergency department use, and while we have to be careful about population size and intervention, we did see a definite reduction in emergency room visits," Jones said in a news release.

Jones's study is published in the Journal of Primary Care and Community Health.