Abstract and Introduction
Abstract
Background The visceral adiposity index (VAI) is a newly-derived measure of visceral adiposity with well-validated predictive power for cardiovascular (CV) outcomes in the general population. However, this predictability has not been investigated in hemodialysis patients, and whether VAI is superior to waist circumference (WC) and waist-to-height ratio (WHtR) in predicting CV outcomes and survival in hemodialysis patients remains unknown.
Methods We performed a prospective study including 464 prevalent hemodialysis patients. The composite outcome was the occurrence of death and CV events during follow-up. Using multivariate Cox regression analysis, VAI, WC and WHtR were tested for the predictive power of outcomes. To evaluate the predictive performance of the VAI, WC and WHtR, time-dependent receiver operating characteristic curve (ROC) analysis was performed.
Results VAI, WC and WHtR positively correlated with each other. Patients with a higher VAI (tertile 3 vs. tertile 1, adjusted hazard ratio (HR), 1.65; 95% confidence interval (CI), 1.12–2.42; tertile 2 vs. tertile 1, adjusted HR, 1.52; 95% CI, 1.1–2.18) had more composite outcomes. VAI had a similar predictive power of all-cause mortality to WC and WHtR, but superior predictive power of composite and CV outcomes to WC when analyzed by a stepwise forward likelihood ratio test. In time-dependent ROC analysis, VAI, WC and WHtR showed similar predictive performance for outcomes.
Conclusion VAI is an optimal method to measure visceral adiposity to assess long-term CV outcomes and all-cause mortality in prevalent hemodialysis patients. VAI may provide a superior predictive power of CV outcomes to WC and WHtR.
Introduction
Visceral adiposity is associated with abnormal lipid metabolism, pro-inflammatory activity and insulin resistance in both the general population and dialysis patients. Increased visceral adiposity can lead to incident diabetes mellitus (DM) and atherosclerosis in the general population, and protein-energy wasting in dialysis patients. It can also lead to cardiovascular (CV) events and mortality. The linkage between dysfunctional visceral adiposity and CV disease has been proven; however, the best way to measure visceral adiposity in chronic kidney disease (CKD) and dialysis patients remains inconclusive. Waist circumference (WC) and waist-to-height ratio (WHtR) are commonly used in dialysis patients to assess visceral fat, and the predictability of mortality in hemodialysis (HD) patients further strengthens the role of WC. Nevertheless, the predictive power of WC on all-cause mortality and cardiac death in dialysis patients depends on the body mass index (BMI), and it has recently been reported to be affected by the interaction between WC and triglycerides (TG) and WC and adipokines. Machine-based measures of fat mass such as computed tomography and dual energy X-ray absorptiometry are precise and reliable, however, they also are extremely costly and complicated to perform in CKD and dialysis patients.
Recently, a newly-derived anthropometric measure of obesity, the visceral adiposity index (VAI),a sex-specific index based on WC, BMI, TG, and high density lipoprotein cholesterol (HDL-C), has been shown to be an indicator of visceral adipose functionality. It has also been strongly associated with cardiometabolic risks and the prediction of CV outcomes, including coronary artery disease and cerebrovascular disease in the general population. However, whether VAI provides superior predictive power for CV outcomes and survival to WC and WHtR remains inconclusive. One landmark study showed that the VAI was better than BMI and WC in the prediction of CV events, however, a large-scale population-based study showed that the VAI is less predictive of incident CV disease than other simple anthropometric measures, such as WC or WHtR. In addition, the utility and the significance of the VAI in dialysis patients have yet to be investigated.
The aim of this prospective study was to investigate whether the VAI is a useful tool to assess CV complications and survival, and to test whether the VAI has superior predictive power of outcomes compared to the commonly used anthropometric measures of visceral adiposity in prevalent HD patients.