Paradox of risk factors for cardiovascular mortality in uremia: Is a higher cholesterol level better for atherosclerosis in uremia?

Patients with chronic uremia have a substantially elevated risk of death fr om cardiovascular disease than do the general population. Although uremic a nd nonuremic groups share some of the risk factors for cardiovascular morta lity, such as older age, diabetes, and Inflammation, other factors appear t o affect cardiovascular mortality in the opposite direction. For example, b eing overweight and having hyperlipidemia are established risk factors In t he general population, whereas lower body mass Index and lower plasma chole sterol have been shown to be risk factors for cardiovascular mortality in e nd-stage renal disease (ESRD). This paradoxical phenomenon is explained by two facts: (1) that malnutrition is a strong predictor of cardiovascular mo rtality In ESRD and (2) that plasma lipid levels are lowered in malnutritio n. However, it is not known whether atherosclerosis Is promoted by malnutri tion or by low cholesterol level. Because the cardiovascular mortality rate is theoretically the product of event rate and fatality rate after an even t, risk factors for cardiovascular mortality could fall into two categories : those raising the event rate and those affecting the fatality rate. Some factors could work both ways. Patients with ESRD show a significant Increas e in both event rate and fatality rate. Dyslipidemia Is an Independent fact or affecting atherosclerotic arterial wall changes and cardiovascular event s in ESRD. Other factors affecting the cardiovascular event rate in ESRD In clude diabetes and an elevated homocysteine level. In contrast, factors ass ociated with poor survival after an event Include diabetes and anemia. Maln utrition could be a factor causing the fatality rate to rise, although ther e Is no direct evidence supporting this possibility. Further studies are ne eded to show the differential effects of a risk factor on event rate and fa tality rate. Patients with ESRD would have a better chance of living longer by better management of the two categories of risk factors. (C) 2001 by th e National Kidney Foundation, Inc.