VANCOUVER, B.C.—Pre-transplant overweight and obesity are associated with a higher risk of delayed graft function (DGF) in renal transplant recipients, data suggest.

Researchers led by Kamyar Kalantar-Zadeh, MD, MPH, PhD, studied 11,836 hemodialysis patients who under renal transplantation from July 2001 to June 2007. Subjects had a mean age of 49 years and a mean body mass index (BMI) of 26.8 kg/m2.

Pre-transplant BMI remained an independent predictor of DGF even after adjusting for demographics and other variables. Each standard deviation increment in BMI was associated with a 35% higher risk of DGF. In addition, compared with patients with a pre-transplant BMI of 22-24.99, those with a BMI of 25-29.99 (overweight), 30-34.99 (mild obesity), and 35 or higher had 30%, 42%, and 118% increased risk of DGF, respectively, the investigators reported at the World Congress of Nephrology. In addition, patients with a BMI above 35 had an 87% increased risk of DGF than those with a BMI below 35.

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“Despite data indicating an obesity paradox with greater survival of overweight and obese hemodialysis patients, careful trials of closely supervised weight reduction may be indicated to examine whether immediate post-transplant outcomes including risk of DGF can be improved,” said Dr. Kalantar-Zadeh, Associate Professor of Medicine and Pediatrics, and Director, Dialysis Expansion & Epidemiology, Harbor-UCLA Medical Center, Torrance, Calif.

A biologically plausible explanation for the study’s findings is that obesity is associated with longer operative time and longer warm ischemic time, which are risk factors of DGF, Dr. Kalantar-Zadeh said.

“Obesity is associated with high sympathetic activity, which results in renal vasoconstriction,” he explained. “Moreover, the prompt administration of calcineurin inhibitors after transplantation, probably in higher doses [because of patient] overweight or obesity, may aggravate vasoconstriction and further compromise graft perfusion, increasing the risk of DGF.”

Another potential explanation is the linkage between obesity and increased pro-thrombotic activity and endothelial dysfunction, he said. “Body fat mass, in particular central obesity, is associated with higher levels of thrombin generation.” Obesity is also a risk factor for venous thromboembolic disease. Increased pro-thrombotic activity and endothelial dysfunction may contribute to the risk of graft microthrombosis, which may play an important role in DGF.