cigarette smoking are traditional systemic risk factors, 10 and the low-density lipoprotein-cholesterol (LDL-C) level is a well-established molecular risk factor. 11 A meta-analysis of 4 randomized trials using conventional IVUS revealed that a decrease in both the LDL-C level and the LDL-C/ high-density lipoprotein-cholesterol (HDL-C) ratio (L/H ratio) after statin treatment was associated with regression of the total atheroma volume in patients with CVD. 12 Although the lipid component of coronary plaques as evaluated by IB-IVUS more precisely reflects the vulnerability of coronary plaques and predicts clinical outcomes compared with evaluation of the atheroma volume using conventional IVUS, 7,13 it has not been determined which coronary risk factors are associated with the serial changes in the lipid component of coronary plaques evaluated by IB-IVUS. Accordingly, we sought to investigate this in the I n the past decade, cardiovascular disease (CVD) has emerged as the leading cause of death worldwide. Most cases of acute coronary syndrome (ACS), which is one of the most traumatic events in CVD, are triggered by the rupture of a vulnerable plaque followed by thrombosis formation at the rupture site. 1,2 Vulnerable plaques are characterized by a large, lipid-enriched necrotic core overlaid with a thin fibrous cap. 3 Pathological studies have revealed that the size of the lipid component of coronary plaques is strongly associated with their vulnerability. 4-6 Integrated backscatter intravascular ultrasound (IB-IVUS) is capable of assessing the lipid component of coronary plaques and can evaluate serial changes in the lipid component during drug interventions. 5,7-9There are many risk factors for the development of CVD; hypertension, dyslipidemia, diabetes, obesity, and