From the enrollment files, we defined each patient's age on the index date, sex, and race (white, black, or other). From claims spanning the 6 months before the index prescription, we ascertained previous diagnoses of complications due to diabetes (nephropathy, dialysis dependency, gastroparesis, retinopathy, and neuropathy), prior use of other diabetes drugs (insulin, sulfonylureas, metformin, and other), and the number of diabetes-related physician visits and hospital admissions. We also defined the presence of prior cardiovascular diagnoses (atrial fibrillation, coronary artery disease, CHF, cerebrovascular disease, hypertension, MI, and peripheral artery disease) and procedures (ie, angiography, coronary artery bypass graft surgery, percutaneous transluminal coronary angioplasty, and stent insertion). Prior use of cardiovascular medications was also ascertained from prescription claims during the 6 months before the first TZD claim, including angiotensin-converting enzyme inhibitors or angiotensin receptor blockers, β-blockers, statins, antiplatelet drugs (ticlopidine hydrochloride and clopidogrel bisulfate), and nitrates. We further captured other comorbidities (ie, chronic obstructive pulmonary disease, dementia, depression, other mental disease, any malignancy, and obesity), prior health care utilization (ie, number of hospital days, physician visits, prescriptions for different generic drugs filled, and any nursing home stay), and calendar year of the index prescription.