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 from cardiovascular disease than do the general population. Although uremic and nonuremic groups share some of the risk factors for cardiovascular mortality, such as older age, diabetes, and inflammation, other factors appear to affect cardiovascular mortality in the opposite direction. For example, being overweight and having hyperlipidemia are established risk factors in the general population, whereas lower body mass index and lower plasma cholesterol have been shown to be risk factors for cardiovascular mortality in end-stage renal disease (ESRD). This paradoxical phenomenon is explained by two facts: (1) that malnutrition is a strong predictor of cardiovascular mortality in ESRD and (2) that plasma lipid levels are lowered in malnutrition. However, it is not known whether atherosclerosis is promoted by malnutrition or by low cholesterol level. Because the cardiovascular mortality rate is theoretically the product of event rate and fatality rate after an event, 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 increase in both event rate and fatality rate. Dyslipidemia is an independent factor affecting atherosclerotic arterial wall changes and cardiovascular events in ESRD. Other factors affecting the cardiovascular event rate in ESRD include diabetes and an elevated homocysteine level. In contrast, factors associated with poor survival after an event include diabetes and anemia. Malnutrition could be a factor causing the fatality rate to rise, although there is no direct evidence supporting this possibility. Further studies are needed to show the differential effects of a risk factor on event rate and fatality rate. Patients with ESRD would have a better chance of living longer by better management of the two categories of risk factors.