We appreciate the interest shown by Oda (1) in our article published in the August issue of Diabetes (2). He suggests that serum bilirubin may be a confounder in the association between A1C and risk of congestive heart failure. A few cross-sectional studies have reported a moderate inverse association between serum bilirubin and A1C (3,4), and some prospective studies have reported that serum bilirubin concentration is inversely associated with cardiovascular risk (5,6). Whether bilirubin is a causal risk factor for the development of cardiovascular outcomes, including congestive heart failure, is unclear (5,–7). Because bilirubin was not measured in the Atherosclerosis Risk in Communities (ARIC) Study, we cannot directly test this hypothesis.
No potential conflicts of interest relevant to this article were reported.