Objective:
Smoking is a risk factor for various diseases such as malignant tumor and respiratory illness, and is one of the most important coronary risk factors. However, few studies have investigated the association between smoking habits and the presence or severity of coronary stenosis as assessed by coronary computed tomography angiography (CCTA).

Methods:
We enrolled 1,008 patients (males:females=492:516, 65±12 y). They had all undergone CCTA and either were clinically suspected of having coronary artery disease (CAD) or had at least one cardiovascular risk factor. We divided the patients into smoking (past and current smoker) and non-smoking groups, and evaluated the presence of CAD, the number of significantly stenosed coronary vessels (VD), and the Gensini score as assessed by CCTA in the two groups. Among 1,008 patients, we selected 416 patients who had the data for Pack-year, and also divided the patients into smoking and non-smoking groups.

Results:
In all patients, percentages of smoker, CAD, hypertension, diabetes and dyslipidemia were 51%, 51%, 64%, 20% and 54%, respectively. The incidence of CAD, VD and Gensini score in the smoking group were all significantly greater than those in the non-smoking group (CAD, p=0.001; VD, p<0.001; Gensini score, p<0.001). In 416 patients, pack-year was significantly associated with VD and Gensini score, and was strongly associated with multi-vessel disease (2- and 3-VD) (p < 0.05).

Conclusions:
Smoking was one of the most important coronary risk factors. In addition, Pack-year may be one of factors that was associated with the severity of coronary stenosis in terms of VD and Gensini score.