PMID- 34627150 OWN - NLM STAT- MEDLINE DCOM- 20220118 LR - 20220118 IS - 1471-2261 (Electronic) IS - 1471-2261 (Linking) VI - 21 IP - 1 DP - 2021 Oct 9 TI - Combined effect of hyperhomocysteinemia and smoking on the severity of coronary artery disease in young adults 15 micromol/L. The severity of coronary artery stenosis was evaluated by Gensini Score. The co-effect of current smoking and HHcy on CAD severity as well as the relationship between plasma Hcy, pack-years of smoking and CAD severity were assessed by multivariate linear regression analysis. RESULTS: A total of 989 participants (mean age, 33 years; 96.2% male) fulfilling the criteria were enrolled in this study. Patients with both HHcy and current smoking accounted for 39.1% of all the subjects. Multivariate liner analysis indicated both serum Hcy levels (beta 0.302; 95% CI 0.141-0.462; P < 0.001) and pack-years of smoking (beta 0.523; 95% CI 0.265-0.781; P < 0.001) were independently associated with the severity of coronary artery stenosis after adjusting for other traditional confounders. In addition, serum Hcy levels were correlated with pack-years of smoking in young CAD patients (r = 0.116, P = 0.001). Moreover, combination of HHcy and current smoking was suggested to have higher risk for CAD severity (beta 17.892; 95% CI 11.314-24.469; P < 0.001), compared with HHcy (beta 7.471; 95% CI 0.009-14.934; P = 0.048) or current smoking (beta 7.421; 95% CI 0.608-14.233; P = 0.033) alone. CONCLUSION: Combination of HHcy and smoking is independently associated with the severity of CAD in young patients