WASHINGTON—Low or high body mass index (BMI) influences dialysis adequacy, according to new study findings presented at Kidney Week 2019 and concurrently published in BMC Nephrology.

Yu-Ji Lee, MD, of Samsung Changwon Hospital in South Korea, and his peers analyzed data from 18,242 maintenance hemodialysis patients on a twice- or thrice-weekly schedule from the Korean Society of Nephrology registry 2001 to June 2017. Of these, 4824 died over a median 5.2 years. Baseline spKt/V was divided into 6 categories for analysis: less than 1.0, 1.0 to less than 1.2, 1.2 to less than 1.4, 1.4 to less than 1.6, 1.6 to less than 1.8, and 1.8 or higher. Cox regression analysis confirmed that, compared to the target range spKt/V of 1.2 to 1.4, lower and higher spKt/V were associated with greater and lower risks for all-cause mortality, respectively.

BMI modified this relationship, Dr Lee’s team found. Patients were grouped by their baseline BMI (in kg/m2): less than 20 (low), 20 to less than 23 (normal), and 23 or more (high). Higher spKt/V was associated with lower all-cause mortality in patients with low to normal BMI. Survival in the high BMI group, however, was not significantly improved at higher doses of dialysis.

Patients with low BMI had a higher risk for all-cause mortality at all spKt/V levels than those with normal BMI and spKt/V within target. The mortality gap narrowed at higher spKt/V values.   

High BMI appeared protective. Patients with high BMI and spKt/V less than 1.2 were not at increased risk for mortality despite low dialysis adequacy, compared with patients with normal BMI and target range spKt/V. Patients with high BMI with spKt/V of 1.2 or greater were actually at lower risk for all-cause mortality than reference patients with normal BMI and target range spKt/V. Increasing spKt/V above target did not provide any additional survival benefit in high BMI patients.

Malnutrition-inflammation complex syndrome and protein energy wasting likely account for the relationship between lower BMI and greater mortality among dialysis patients, Dr Lee’s team stated. Smaller patients, who have a lower urea distribution volume, also tend to experience higher post-dialysis urea rebound and greater generation of uremic toxins per unit of body mass, they noted.

High BMI, however, may indicate good nutritional status and outweigh the influence of dialysis adequacy, Dr Lee’s team explained.

References

Yang KH, Lim Y, Lee YJ.The Association of Dialysis Adequacy, Body Mass Index, and Mortality Among Hemodialysis Patients. Presented at the American Society of Nephrology’s Kidney Week 2019 meeting held November 5 to 10 in Washington DC. Abstract SA-PO1040.

Hong WP and Lee YJ. The association of dialysis adequacy, body mass index, and mortality among hemodialysis patients. BMC Nephrol.