Renal function impairment relates to poor outcome in patients with chronic heart failure (HF). Differences in biological aging could affect the susceptibility to develop renal dysfunction in chronic HF. In the present study, we explored the association of leukocyte telomere length with renal function in patients with chronic HF. We studied 610 patients with HF, aged 40 to 80 years, NYHA class II-IV, with left ventricular ejection fraction of 0.40 or less. Glomerular filtration rate was estimated by the Modification of Diet in Renal Diseases (MDRD) formula, and telomere length of leukocytes was determined by a validated quantitative polymerase chain reaction- based method. Age-and gender-adjusted telomere length ratio decreased steadily with decreasing quartile of the MDRD formula (mean 0.80, 95% confidence interval [CI] 0.73 to 0.88; mean 0.74, 95% CI 0.68 to 0.81; 0.70 mean, 95% CI 0.63 to 0.76; mean 0.67, 95% CI 0.61 to 0.73; p <0.01). Telomere length of leukocytes correlated positively with the MDRD formula (correlation coefficient 0.141; p <0.001). These findings remained significant after adjustment for baseline differences and sensitivity analysis based on propensity score one-to-one matching. In conclusion, shorter leukocyte telomere length is associated with decreased renal function as estimated by the MDRD formula in patients with HF. Further studies will be needed to determine whether shorter leukocyte telomere length is the cause or consequence in this population and whether it plays a role in the prognosis of renal dysfunction in HF. (C) 2008 Elsevier Inc. All rights reserved.