November 6, 2009 (San Diego, California) - Extra body weight could mean a longer life for dialysis patients, according to findings presented here at Renal Week 2009: American Society of Nephrology (ASN) 2009 Annual Meeting.
In a study of more than 600 patients at 8 dialysis clinics, 5-year mortality was 2.5 to 3 times higher among people with less than 10% body fat than among people with 20% to 29% body fat. These findings suggest that adiposity might somehow have a protective effect in this population, said Debbie Benner, MA, RD, national director of nutrition services for the DaVita chain of dialysis clinics across the United States and based in Torrance, California.
The fattest group, with 40% body fat or more, had the highest survival rates.
This is an illustration of the "obesity paradox," in which more body fat, even obesity, is associated with better survival among dialysis patients, Ms. Benner explained.
Other investigators have noted similar findings in patients with other serious illnesses, including cancer and heart disease. The reasons for the paradox remain unknown, although one possible explanation is that leptin, a hormone secreted by fat tissue, contributes to a robust immune response to insults such as ischemia, which lead to myocardial infarction. Skinnier people might have a weaker response.
In this study, the investigators measured the body fat, using near-infrared interactance, of 671 patients undergoing dialysis at 8 DaVita clinics from 2001 to 2006, and then measured 5-year survival. The patients had a mean age of 54 years, 52% were male, 54% were diabetic, and 30% were African American. The patients were divided into quintiles, on the basis of body fat, which ranged from less than 10% (n = 34) to more than 40% (n = 89); average body fat content was 27%.
Five-year survival among people in the lowest quintile was 85% of that of the reference group. Among people in the highest quintile, 5-year survival was 29% longer than that of the reference group.
Weight is a complex issue for dialysis patients, Ms. Benner noted. They require a restricted diet that does not tax their kidneys and are warned not to drink too much fluid between dialysis treatments, also in an effort to prevent an undue burden on their kidneys. However, the findings from this study suggest that being too thin also has its risks.
"The key point is that we need to pay attention to what our patients eat, with a focus on appropriate calories and protein and restricted sodium," said Talat Ikizler, MD, associate professor of medicine at Vanderbilt University in Nashville, Tennessee, and medical director of the university's dialysis unit. Dr. Ikizler, who was not involved in this study, added: "I think people must take into account that we can't do with these patients what we do with the general population, which is to try to get them to lose weight. The needs and intake of dialysis patients are very different."
Ms. Benner and Dr. Ikizler have disclosed no relevant financial relationships.
Renal Week 2009: American Society of Nephrology (ASN) 2009 Annual Meeting: Abstract SA-PO2567. Presented October 31, 2009.
