African Americans with hypertension-associated kidney disease were more likely to develop end-stage renal disease (ESRD) than to die, researchers conducting a long-term cohort study said.…
According to Tahira Alves, MD, of the University of Texas Health Science Center in San Antonio, in an 11-year study of more than 1,000 black patients with hypertensive nephrosclerosis, the overall mortality rate was 2.2 deaths per 100 patient-years, whereas ESRD developed at a rate of 3.9 cases per 100 patient-years (P<0.001).
They also found that patients were five times more likely to develop ESRD than to suffer a fatal cardiovascular event (risk ratio 5.01, 95% CI 3.77 to 6.66) — contrary to earlier studies in other populations in which most patients died of cardiovascular disease before reaching ESRD.
However, the authors drew no conclusions on the role of race in these differing results, as the study’s methods also differed markedly from the earlier analyses in a variety of ways.
“The observation of low rates of mortality and cardiovascular disease events compared with ESRD events is noteworthy and warrants further evaluation within both a clinical and a public health context,” Alves and colleagues wrote.
Their data came from the African American Study of Kidney Disease and Hypertension, which initially enrolled 1,094 patients in 1996 and followed them through 2001.
Beginning in 2002, 691 of the 764 participants who had not suffered an event during the first phase agreed to be followed for another six years, for a total of 11 years in the study. A total of 318 cases of ESRD developed during those years, compared with 177 deaths from all causes occurring prior to ESRD onset, of which 59 were from cardiovascular disease.
Alves and colleagues found significant differences between patient subgroups in the relative rates of ESRD to cardiovascular death.
None of these were particular surprising. Subgroup characteristics affecting the likelihood of ESRD versus cardiovascular death as the first outcome were those commonly associated with increased cardiovascular risk (age more than 55 and history of previous cardiovascular disease at baseline) and those that would predict earlier ESRD (baseline urine protein-to-creatinine ratio and estimated glomerular filtration rate).
The findings contrast sharply with earlier analyses of patients with chronic kidney disease. A 2005 study of more than one million Medicare patient records found that cardiovascular deaths outnumbered dialysis initiations by up to 5- to 10-fold.
Another study of 28,000 patients in an insurance-claims database suggested that, even among patients with stage IV kidney disease, the risk of cardiovascular death was double that of ESRD.
Alves and colleagues noted that the populations and methods in these studies were markedly different from their cohort study, which could explain at least some of differences in results.
Not only did the earlier research focus on mostly white patients, but they were either retrospective records analyses or involved patients at much higher baseline risk for cardiovascular disease and death.
Alves and colleagues also noted that their cohort participants, who all had recognized hypertensive illness, had relatively aggressive blood pressure control. This “may have selectively reduced cardiovascular disease but not chronic kidney disease progression,” the researchers wrote.
The study collected data on the type and success of blood pressure control treatment, but there were not enough participants to reach meaningful conclusions as to whether either factor influenced outcomes.
They added that their patients’ participation in the cohort study may itself have helped ward off cardiovascular and all-cause death, insofar as patients had routine and easy access to healthcare.
Fried added that the overall message from the accumulated evidence — that the risk of death before dialysis may vary — doesn’t yet have a clear clinical implication.
“Although it could affect the focus on preparing for dialysis or transplantation evaluation, we would need to improve our risk prediction on an individual level before this could be initiated,” Fried wrote.
- Explain to interested patients that cardiovascular disease often accompanies chronic kidney disease. Some previous research had indicated that patients with chronic kidney disease are likely to die of cardiovascular causes before kidney failure requiring dialysis occurs.
- Explain that patients with chronic kidney disease can take steps to reduce both the risk of premature death and the likelihood of needing dialysis.