Through the 1990s and into the 2000s, as public awareness about the need for organ transplants grew, the number of people who became donors - living and deceased - increased by several hundred each year.
In the last four years, however, that number has leveled off. Last year, total donors were down slightly nationwide. Locally, there was a bigger drop.
Pennsylvania saw a 6.6 percent decline in the number of people who were organ donors last year, while New Jersey's number fell 7.9 percent, according to data collected by the United Network for Organ Sharing, a federal contractor that manages the U.S. transplant system.
The Gift of Life Donor Program, which oversees organ donation in eastern Pennsylvania, South Jersey, and Delaware, saw its total donors drop from 429 in 2009 to 392 in 2010, or 8.6 percent.
Experts say it may be too early to tell the exact cause. But the poor economy and advances in care probably played a role.
Organ donation relies on trust in the system from donors and their families, who must provide consent, said Arthur Caplan, director of the University of Pennsylvania Center for Bioethics and an expert on transplantation.
A tough economy, in which people are skeptical about whether they are getting the best care for their money, "threatens altruism," Caplan said. "It makes people wary that they're going to be getting treated fairly or that the rich are getting an advantage."
That wariness may make people less likely to sign up for organ donation when they renew their driver's licenses or to consent to donating the organs of a loved one, Caplan said.
In central and North Jersey, families were no less likely than in prior years to consent to donation when asked, said Joe Roth, chief executive officer for New Jersey Organ and Tissue Sharing Network. Still, because fewer people were eligible, the organization's number of total donors dropped 15.8 percent in 2010, from 184 in 2009 to 155.
New ways of treating people who have suffered brain injuries - the primary route through which a person becomes a donor - have shrunk the pool of candidates, he said. Those include such treatments as lowering a person's body temperature to slow damage or removing a portion of their skull to relieve the pressure caused by swelling.
Also, he said, more families may be deciding, along with their doctors, to stop treating a patient who is approaching brain death, to avoid costly care that has little chance of working. That shortens the window of time in which groups like Roth's can obtain consent and begin the transplant process, he said.
Kidney and liver donations have taken the hardest hit, just as the demand for both continues to increase. Last year, a record number of Pennsylvanians - 2,503 - were added to the waiting list for a kidney.
Philadelphia is a major hub for transplantation, with eight centers.
As medical director of the trauma program at the Hospital of the University of Pennsylvania, Patrick Kim works at the beginning of the process here. He helps to identify potential donors in the intensive-care unit and has seen a drop in the number of patients who are eligible.
It could be a short-term fluctuation, he said, or it could reflect advancement in care for people with brain injury or stroke, who otherwise would become donors.
"We would like to think that our care is getting better with time," he said.
Kim, who also sits on the hospital's council on donation, said the group was considering creating a team of specialists to focus on the critical time between the death of a donor and the transplant, to preserve the organs and "really maximize that gift."
While total donors were down last year, the number of actual transplants rose nationally and suffered a lesser decline in the region. That's because each donor can supply multiple organs.
Transplant specialists will gather for a national conference in Philadelphia at the end of April to discuss, among other things, how best to manage those organs that are available.
The United Network for Organ Sharing has proposed changing the distribution of kidney donations. Instead of going to whomever is top on a waiting list, the new protocol would send the healthiest kidneys - the top 20 percent - to the healthiest people.
The change is designed, in part, to prevent the best organs from going to patients who have a short life expectancy. Critics say it could manipulate the supply in unforeseen ways and would not do enough to address shortages overall.
"There's no right way or wrong way" to distribute organs, said Richard Hasz, vice president for clinical services at Gift of Life. "Every way in which we do it will have flaws. . . . In the end, the only way to really solve the allocation problem is by supplying more organs."
Lungs are already distributed using a complicated formula that matches organs to patients. But Samuel Goldfarb, medical director for the lung-transplant program at Children's Hospital of Philadelphia, said there just were not enough organs.
"We have kids who have been waiting for over a year, sometimes two," he said. "The limiting factor is finding the organs."
The drop in supply is troubling, he said.
Hasz said one possible cause, particularly for kidneys, was that transplant centers had become more choosy, recognizing that older, less-healthy kidneys could produce poor results for recipients. Older people who may have once been considered for donation are being passed over, he said.
His organization performs regular reviews of the 155 acute-care hospitals in its coverage area and works with them to improve their "consent rate," or how often the families of eligible donors agree to participate.
"We're continuing to grow," Hasz said. "We've just got to keep at it."
Contact staff writer Chelsea Conaboy at 215-854-4193.