BALTIMORE Very obese people who need a kidney transplant are far less likely to get one than normal weight people, and when they do, their wait is an average of a year to 18 months longer, a new study found.
The reason seems to be both economic and medical. Very obese people have a greater risk for complications, and the transplant centers often must bear the additional cost of treating those problems.
The study showed that morbidly obese patients those who average about 100 pounds over their ideal weight were 44 percent less likely to get a transplant than normal weight patients. Those just slightly less obese were 28 percent less likely to get a transplant, the researchers found.
The results also mean very obese patients are more likely to die; each year about 8 percent of all patients waiting for a transplant die.
The research was based on an analysis of records of 132,353 patients on the national kidney transplant waiting list between 1995 and 2006. The work was published Wednesday in the Journal of the American Society of Nephrology.
Obesity can be a reason to exclude a potential transplant recipient because of the risk for complications.
However, once someone has been accepted for the waiting list, that patient is supposed to progress to the top as time passes, said Dr. Dorry Segev, the Johns Hopkins University transplant surgeon who led the study.
Segev said he did not believe doctors or transplant staff were consciously choosing slimmer candidates over obese patients. However, he said two factors may be combining to create the bias.
The main insurer for kidney transplants, Medicare, pays a fixed rate regardless of the difficulty of each case, meaning the transplant hospital bears the burden of added costs for complications. And transplant centers with lower survival rates risk losing Medicare funding.
"I don't think any of this is conscious," Segev said. "It would be hard to imagine any of us in our field would deliberately act against the welfare of our patients. That's not what we do, but there are all sorts of subconscious forces that are happening and there's clearly an unintended bias in practice."
Segev's group found the wait to get a transplant increased along with the patient's body mass index, a height-weight formula. Non-obese patients waited on average 39 months, the overweight waited 40 months, the obese waited 42 months, and the severely and morbidly obese, waited 51 and 59 months, respectively, the researchers found.
Transplant centers normally won't give an organ to a patient with a body mass index over 40, which is morbidly obese, said Dr. Benjamin Philosophe, head of transplantation division at the University of Maryland Medical Center. Such patients are at higher risk for a number of complications.
However, Philosophe said he and many doctors "will give them the benefit of the doubt that they will lose the weight and will put them on the list hoping that while they lose that weight they will accumulate waiting time."
Patients who fail to lose weight can be placed on inactive status, Philosophe said.
Also clouding the issue is the fact the database maintained by the United Network for Organ Sharing does not capture all details on patient condition, said Dr. Kenneth Andreoni of the University of North Carolina School of Medicine, vice chairman of the UNOS kidney transplantation committee.
For example, whether a candidate has diabetes is simply a yes or no checkoff. The lack of more detail on diabetes and other conditions can make it difficult to draw conclusions, he said.
The UNOS official noted that obese patients who never would have been referred for a transplant in the past are now put on the waiting list and rules changes have taken effect over the 11 years studied.