Ontario's Trillium Gift of Life Network said in a release only 39 percent of the 2.5 million registered organ and tissue donors in the province are over the age of 50.
Yet almost two-thirds of the 1,529 patients waiting for an organ transplant in Ontario are 50 years of age or older, the agency said.
In the province, potential organ donors can register when renewing driver licenses or by visiting the www.BeADonor.ca website.
Ontario's organ and tissue donor registration rate as of Sept. 30, 2012 was 22 percent, the release said.
Ronnie Gavsie, president of the network, said of 9 million people not registered to donate organs and tissue in Ontario, 45 percent of them are 50 years of age or older.
Similar concerns exist in the United States.
The U.S. Department of Health and Human Services' website says 59.9 percent of transplant recipients in 2011 were over the age of 50.
"That year, 2,242 deceased donors were between 50–64 years of age," the department says. "Five hundred and ninety-five deceased donors were 65 or older."