Risk factor paradox in hemodialysis: better nutrition as a partial explanation

The higher mortality rate in patients on hemodialysis is primarily due to the higher rate of cardiovascular disease. Yet, paradoxically, overweight, hypertension, and hyperlipidemia, which are cardiovascular risk factors in the general population, have been reported to correlate with better patient survival in hemodialysis. To examine whether this "risk factor paradox" in hemodialysis is due to the positive influence of accompanying better nutrition, we prospectively obtained data on fasting lipids, biochemical markers of nutrition, body mass index (BMI), and blood pressure (BP) in 453 hemodialysis patients and related them to 1 year mortality. As previously noted, body weight, blood pressure, and certain serum lipids positively correlated with survival. Serum prealbumin, one of the most sensitive and specific biochemical markers for nutrition, correlated positively with hypercholesterolemia (r = 0.30, p < 0.001) and BMI (r = 0.12, p < 0.02), but not with mean arterial pressure (MAP) (r = 0.01, p = NS). By analysis of variance, patients in the upper tertile (i.e., higher levels) of BMI and cholesterol but not MAP had significantly higher serum prealbumin and creatinine compared with those in the lower tertile. Our data lend support to the hypothesis that, in patients on hemodialysis, the positive effect of higher BMI and hyperlipidemia but not of high BP could be partially explained on the basis of the accompanying better nutrition. Although not proven, correcting risk factors while improving nutrition may offer better outcomes for patients on dialysis.