Flow diagram of study cohort. Our baseline population was derived from a cohort of 100,441 patients who initiated hemodialysis from 7/1/2010 to 6/30/2011, of whom 46,634 were >67 years old, and has been previously described. Of this cohort of elderly patients, 29,178 initiated hemodialysis with a catheter only, without a maturing AVF or AVG. We then excluded (1) patients without pre-ESRD Medicare claims, (2) those with pre-ESRD AVF/AVG surgeries, (3) those who did not receive an AVF/AVG within 6 months of initiating hemodialysis, and (4) those who received a kidney transplant or switched to peritoneal dialysis. The final study cohort consisted 9,458 elderly patients who initiated dialysis with a CVC and who received an AVF (n=7,433) or an AVG (n=2,025) during the 6 months after dialysis initiation. Note: Grey shading indicates access outcome occurred.