Approximately 1,400 people in the United States are waiting for a lung transplant, according to the U.S. Organ Procurement and Transplant Network. The median wait time for a lung transplant is four months, and more than 200 people die annually while waiting for a lung transplant.

Using lungs from older donors could save lives by making more organs available, but many donor centers have an age cut-off of 45 or 50 years in addition to other criteria.

The age of a donor lung does not appear to have a significant influence on the five-year survival rates among younger recipients of double-lung transplants, according to a new study published in the journal Annals of Thoracic Surgery. The results of the study do show a link between older donor lungs and an increased risk for death among younger single-lung recipients, however.

"The availability of suitable donor lungs for transplantation continues to be a major obstacle to increasing the number of lung transplants performed annually," lead author of the study, Dr. William Whited, said in a press release. "Research such as this that explores the means of expanding the donor pool is of critical importance."

Survival rates for lung transplant recipients have remained stable over the past 30 years, according to the Lung Institute, while the short-term survival rates of 30 days and one year have improved steadily over time. Those who undergo a lung transplant often survive three years or more after surgery. In fact, more than half survive longer than five years.

Prognosis depends largely on the recipient's age, gender and diagnosis, the length of organ storage time, type of lung transplants, and patient response. The result of the new study suggests donor age is less important for double-lung transplant survival rates.

The researchers analyzed data from the United Network for Organ Sharing database, queried between January 2005 and June 2014. The scientists included information about lung transplant patients who were at least 18 years old into the study. Doctors performed 14,222 lung transplants during the study period. The researchers stratified patients by recipient age of 50 years or less, donor age of 60 years and older, and single- versus double-lung transplantation.

Only 2 percent of recipients age 50 or younger received organs from lung donors over the age of 60, and a mere 4 percent of all lung transplants involved organs from older donors.

Older donor lung age was associated with worse survival among recipients over the age of 50 who received single-lung transplants. Donor lungs aged 60 or older were associated with a slightly worse five-year survival rate than were lungs from younger donors, at 44 percent versus 52 percent.

Among recipients aged 50 and older, receiving older lungs were associated with worse five-year survival with the use of single-lung transplants compared with double-lung transplants, at 15 percent and 50 percent respectively. The researchers found no significant difference in survival between those receiving lungs from young and old donors for double-lung transplant.

The researchers from the University of Louisville concluded that clinicians should consider older lungs for double-lung transplants, as appropriate, for both older and younger recipients.

"There is probably an untapped resource of lungs from older donors, and I think we should strongly consider being more aggressive in using them," researcher Matthew P. Fox, M.D., told MedPage Today.

"It's true that typical older donor lungs are not as good as younger lungs. If you asked me if I'd rather have lungs from a 30-year-old or a 60-year-old for a transplant, I'd take the 30-year-old lung every time. But there just aren't that many younger donors."