Australasian Science: Australia's authority on science since 1938

Diabetes Determines Lung Transplant Success

By Stephen Luntz

Diabetes is the strongest risk factor for the death of lung transplant recipients, according to Dr Kathryn Hackman.

Hackman, a PhD student at Monash University, studied 386 lung transplants performed at The Alfred Hospital in Melbourne between 2001 and 2010. “The patients with diabetes were not dying of stroke, cardiovascular disease or other diabetes-related illnesses. The main cause of death in all transplant patients was a lung condition known as bronchiolitis obliterans, which is a form of chronic rejection of the transplanted organ,” Hackman says. “This suggests that diabetes could be affecting the transplanted lungs and causing them to fail earlier.”

Diabetes is a common consequence of the steroids and other immune-suppressing drugs given to transplant patients. “Transplant physicians haven’t treated it too aggressively,” Hackman says, “because the classic complications of diabetes take years to develop and the life expectancy of people with lung transplants is usually less than 10 years.”

Some of the patients in Hackman’s study had Type 2 or cystic fibrosis-related diabetes prior to the transplant, while others developed high blood sugar levels in what is known as post-transplant diabetes. This can be transient but in some cases proves permanent, particularly if untreated.

Hackman presented her results at the annual conference of the American Endocrine Society, and reported that she had assessed diabetes along with a range of other risk factors, such as age, transplant type, underlying lung disease, body mass index and cholesterol.

However, diabetes proved a more important predictor than any of them. Those without it lived an average of 10 years after the transplant – twice as long as those who had the condition.

“We don’t know why diabetes raises the risk of bronchiolitis obliterans,” Hackman says. “We know from general population studies that diabetes affects the lungs, and patients with Type 2 diabetes have more rapid decline in lung function.

“In animal models it thickens the air–blood barrier. We’d like to stain lung tissues for fibrosis and see if there is a difference between those with and without diabetes.”

“We found no difference in survival between patients whose diabetes was diagnosed before transplant and those whose diabetes was newly diagnosed after,” Hackman says. Consequently she thinks that pre-existing diabetes is unlikely to become a factor in determining a patient’s eligibility to receive lung transplants. Future research will determine whether strict blood sugar control will improve survival.