BMI ≥30 kg/m2 is defined as a positive risk factor. Metabolic syndrome is defined

by the criteria license with Pfizer of the National Cholesterol Education Program as the presence of three or more of the following: (1) abdominal obesity; (2) elevated triglyceride levels (≥150 mg/dL); (3) decreased high-density lipoprotein cholesterol (HDL-C) levels (<40 mg/dL for men and <50 mg/dL for women); (4) high blood pressure (systolic blood pressure ≥130 mmHg, diastolic blood pressure ≥85 mmHg or use of antihypertensive medication); and (5) elevated fasting glucose levels (≥110 mg/dL).[27] Abdominal obesity is defined as a waist circumference of ≥90 cm for men and ≥80 cm for women according to the revised Asia-Pacific criteria suggested by the World Health Organization Western Pacific Region [28]. Clinical data collection The physician responsible for consideration of the patient for DSA fills out

a standardised data collection form to collect information on age, gender, pattern of cerebral atherosclerosis (lesion location and severity), cardiac disease, DM, HTN, family history, dyslipidaemia, previous stroke history, alcohol history, metabolic syndrome and BMI, medical history and current medication. Patients’ angiographic findings and medical records are recorded prospectively to assess patient demographics; however, additional smoking history is assessed retrospectively by telephone to obtain the data in sufficient detail. Statistics and Study outcome Distribution of patient age, gender, lesion location (AC vs. PC, IC vs. EC, and ID vs. ED) and number (single vs. multiple) are correlated with the history of smoking. We also evaluate the proportion of patients with IC atherosclerotic stenosis among smokers and compare this with the proportion in patients stratified by the other risk factors. Differences in risk factor distribution are analysed according to age in 10 year intervals. Categorical variables are presented as frequencies and percentages, and continuous variables are expressed

as mean and SD. The t test is used to compare continuous variables, and the chi-square test or Fisher exact test are used to compare categorical variables, as appropriate. Associations between risk factors (age, gender, location, multiplicity, smoking, etc.) and IC atherosclerosis stenosis are tested by using the univariate Dacomitinib logistic regression model followed by the multivariable logistic regression model with backward elimination. All reported p-values are two sided, and P<.05 is considered statistically significant. Statistical analyses are conducted using SPSS 21 software (SPSS Inc., Chicago, IL, USA). SUMMARY This analytical cohort study is designed to investigate the association between IC atherosclerotic stenosis and smoking, adjusting for confounding by other risk factors. We anticipate that it will have the power to detect any relationship between smoking and IC atherosclerotic lesions especially in younger patients.