In a recent article at NPR on organ donation waiting lists and how those who need organ transplants wait longer than others due to geographical location, a fact popped up that took me by surprise.

One big reason for that is that more organs become available in some places than others. And that’s partly because of the way people die — there are more deaths in ways that leave the victims eligible to be organ donors, such as car accidents and strokes.

“The heroin epidemic has actually led to a lot of organ donors because when people become overdosed they stop breathing and they become brain dead,” Heimbach says. “And certain areas of the country have more or less of that particular problem.”

Generally, more livers tend to become available in rural places than in more urban places, such as California, New York City and the Washington, D.C., area.