Body Measurements Predict Dialysis Patient Outcomes
Declines in mid-arm circumference (MAC) are significantly associated with increased all-cause mortality and cardiac outcomes among hemodialysis (HD) patients, a study found. The associations were especially pronounced among patients with a low body mass index (BMI, 25 kg/m2 or less).
In addition, declines in skinfold thickness were significantly associated with outcomes only among patients with a low BMI.
The study, by Mark L. Unruh, MD, MS, of the University of New Mexico in Albuquerque, and collaborators, examined data from 1,846 patients enrolled in the Hemodialysis (HEMO) Study. Researchers looked at how changes in MAC and skinfold thickness—which are an indication of nutritional status—affect all-cause mortality, cardiac death and hospitalization, and infection-related death. Poor nutritional status is associated with worse HD patient survival.
During a median follow-up of 2.5 years, 845 deaths occurred. MAC and skinfold thickness declined 0.26 cm and 1.1 mm per year, respectively, according to findings published online ahead of print in the American Journal of Kidney Diseases. Each 1 cm per year faster decline in MAC was associated with a significant 2.4 times increased risk of all-cause mortality among patients with a low BMI, but was not associated with a significantly increased risk among those with a high BMI (above 25). Each 1 cm per year faster decline in MAC was associated with a significant 54% and 47% increased risk of cardiac death or hospitalization among patients with a low and high BMI, respectively, and a fivefold increased risk of infection-related death among patients with a low BMI.
Among patients with a low BMI, a 1 mm per year faster decline in skinfold thickness was associated with a 22% increased risk of all-cause mortality and an 83% increased risk of infection-related death.
Dr. Unruh's team noted that higher BMI in dialysis patients is considered a protective predictor of patient survival, an association that has been called the obesity paradox. Their results suggest that in HD patients with a BMI of 25 or less, “a decline in muscle mass and body fat potentially could affect mortality risk and this same risk is not observed in overweight or obese hemodialysis patients,” they wrote.