THURSDAY, March 22 (HealthDay News) -- The age of a live kidney donor has little effect on the long-term health of a transplanted kidney in recipients older than age 39, a new study says.

The findings should encourage more people to participate in living donor paired-exchange programs ("kidney swaps"), said Dr. John Gill, of the University of British Columbia in Vancouver, and colleagues.

In kidney-swap programs, a donor whose kidney isn't compatible with a loved one who needs a new kidney instead donates a kidney to a stranger. In return, the donor's loved one receives a kidney from someone else.

The researchers analyzed data from all adult kidney transplants from living donors that were performed in the United States between January 1988 and December 2003. Follow-ups continued through September 2007.

The age of the kidney donors, which ranged from 18 to 64 years, had minimal effect on the survival of transplanted kidneys in recipients older than age 39. Recipients ages 18 to 39 benefited the most when they received kidneys from donors in the same age group.

The study appears online March 22 in the Clinical Journal of the American Society of Nephrology.

"This information should help increase participation and efficiency of living donor paired-exchange programs because it alleviates patient concerns about receiving a kidney from an older-aged living donor," Gill said in a journal news release.

Nearly 90,000 people in the United States are waiting for a kidney transplant, according to the release, and many will die before a suitable kidney becomes available. Kidney-swap programs help increase the donor pool.

More information

The National Kidney Foundation has more about kidney transplantation.