By Lexa W. Lee
Chronic kidney disease (CKD) is an independent predictor of mortality in patients with peripheral vascular disease (PVD), while obesity is not, according to a study presented at the 2011 American College of Cardiology meeting. Previous data indicates that CKD, defined as a glomerular filtration rate (GFR) of less than 60 ml/min/1.72 m², is associated with increased risk for all-cause mortality, cardiovascular disease, and progression to renal failure. There is a persistent long term mortality rate of approximately 50% among PVD patients.
“The 10-yr mortality rate is as much as 75% in severely symptomatic patients and 45% in asymptomatic patients,” said lead author Ashwin Bhirud, 4th year medical student at West Virginia University in Charleston, West Virginia.
Significant increases in cardiovascular events also correspond with increasing obesity in PVD patients. There is a 2.35-fold increased risk with a BMI >= 30. Interestingly, some studies have demonstrated an obesity paradox in which overweight or obese patients have better outcomes than non-overweight patients. The actual effects obesity and chronic kidney disease (CKD) have on mortality on PVD patients is not well understood.
The aim of this retrospective study was to evaluate the impact of obesity and CKD on all-cause mortality in PVD patients at time points of 30 days, 1 year, and 3 years.
The researchers examined the records of 303 consecutive patients aged at least 50 years who underwent either endovascular or surgical procedures for PVD between January 1, 2006 and December 31, 2007. The investigators classified patients as obese or non-obese groups, which were further subdivided into 2 groups based on GFR levels above or below 60 ml/min/1.72m2. The 30-day, 1-year, and 3-year follow-up survival data were obtained from the Social Security Death Index.
Of the 303 patients examined, 86 patients (28%) were obese and 217 (72%) were non-obese. Mortality at 30 days for the obese group vs the non-obese group was 4% and 7%, respectively,
p = 0.29; at 1 year, 17% vs 20%, p = 0.41; at 3 years, 30% vs 34%, p = 0.5. There were 129 PVD patients with a GFR < 60 ml/min/1.72m2 and 174 with a greater GRF. Mortality at 30 days for the lower GFR group vs the higher GFR group was 9% and 1%, respectively, p = 0.013; at 1 year, 26% vs 12%, p = 0.001; at 3 years, 43% vs 22%, p < 0.001.
The researchers concluded there is no significant association between BMI and mortality, indicating that obesity is not an independent predictor of mortality in PVD patients. However, chronic kidney disease with GFR < 60 ml/min/1.72m2 is a predictor of increased short term (30 days) and long term (1 and 3 year) mortality, even when correcting for the presence of other co-morbidities. This suggests that controlling the progression of kidney disease might reduce the risk of mortality in PVD patients.
Asked whether the finding that obesity was not a significant predictor of mortality in PVD was surprising, Bhirud said, “A little bit, because there are some other risk factors associated with obesity, associated with metabolic syndrome, that do predispose to mortality. It’s possible that with increasing the number of patients, we may tease out a difference, over a longer period. But it [obesity] was insignificant over the time of follow-up. It would be nice to look at specific risk factors associated with metabolic syndrome like cholesterol and blood pressure and see if those, independent of obesity, have an effect also on patients with peripheral vascular disease, and find ways to decrease risk in those patients.”
Author Disclosures: Author reports no disclosures