SAN FRANCISCO — Increased levels of fitness attenuated a higher risk of death in women with impaired renal function in a 16-year study of 5,716 participants who were asymptomatic at baseline.
Estimates of glomerular filtration rate (GFR) and fitness should be added to use of traditional cardiovascular risk assessments to help stratify risk and prioritize intervention in selected patients, Dr. Martha Gulati said at the annual meeting of the American Society of Hypertension.
The study recruited community women in 1992 who had no known renal or heart disease and compared baseline urinalyses, estimated GFR, and estimated fitness as measured by metabolic equivalent units (METs) with all-cause mortality in 2008.
At baseline, 79% of the women had a GFR of less than 60 mL/minute per 1.73 m2, putting them at higher risk for chronic kidney disease and cardiovascular disease than women with a higher GFR. The mostly white cohort had a mean age of 53 years and a mean waist circumference of 33 inches. Fifteen percent were smokers, 45% had hypertension, and 5% had diabetes. Overall, at baseline “this was a relatively healthy cohort with a really good level of fitness,” based on a mean of 8 METs, said Dr. Gulati of Northwestern University, Chicago.
In an analysis that adjusted for the effects of traditional cardiovascular risk factors using the Framingham risk score, a creatinine level greater than 1.4 mg/dL increased the risk of mortality by 80%, compared with lower creatinine levels. Every unit increase in GFR decreased mortality by 3%, Dr. Gulati reported.
When exercise capacity was added to the analysis, these variables remained significant predictors of risk. Compared with those who had a GFR below 45 mL/minute per 1.73 m2, the mortality risk was 37% lower in the 66% of the cohort who had a GFR of 45-59, and 46% lower in the 21% of the cohort with a GFR of at least 60. About 75% of the lowest-GFR group was alive 16 years later, compared with 91% in the intermediate-GFR group and 94% in the highest GFR group.
In each of the GFR subgroups, women with better baseline fitness were less likely to die. Mortality rates (per 1,000 person-years) in the lowest GFR group were 3.18 at the highest fitness levels (greater than 8 METs), 3.81 with intermediate fitness (5-8 METs), and 7.62 among the least fit (less than 5 METs).
In the intermediate GFR group, mortality rates were 0.98, 1.76, and 3.16 per 1,000 person-years in the highest, intermediate, and lowest fitness subgroups.
In the highest GFR group, mortality rates were 0.56, 1.18, and 1.68 per 1,000 person-years in the highest, intermediate, and lowest fitness subgroups.
Dr. Gulati disclosed that she has been a speaker for AstraZeneca and Fujisawa Healthcare and has received research funds from the latter.