Fewer patients with brain injury are being declared "brain dead," which may explain the declining rates of deceased organ donation, researchers in Calgary say.

Patients with neurologic death — irreversible stop of cerebral and brainstem functions, including respiration — are the main source of organ donations for transplant. Knowing that hospital death rates have decreased over time for critically ill patients with brain injury, researchers in Alberta checked to see if the proportion of patients with brain death also decreased for a group of 2,788 ICU patients in southern Alberta over nearly 11 years.

It did. The percentage of patients with neurologic death was 8.1 per cent in 2002, 9.6 per cent in 2004, 2.2 per cent in 2010, and just over 4 per cent in 2012, study author Dr. Andreas Kramer, medical director of the Southern Alberta Organ and Tissue Donation Program and co-authors said in Monday's issue of the Canadian Medical Association Journal.

"Our finding that a reduced proportion of patients with brain injury progressed to neurologic death suggests that initiatives aimed at improving road safety, preventing injuries during recreational activities, and improving pre-hospital and in-hospital care, have had an effect and should continue to be promoted," the researchers concluded.

To increase organ transplantation rates, alternative approaches will be needed, they said, such as living donation, donation after cardiocirculatory death and innovations to improve the use of donated organs.

The researchers couldn't determine the reasons for their finding. But the results are consistent with Alberta Transportation and Transport Canada trends showing a decrease in annual traffic-related fatalities.

The care of patients with brain injury has also improved during the time frame of the study, such as surgery to help relieve pressure on brain swelling and more specialists in neurocritical care.