Copyright © 2021 Wolters Kluwer Health, Inc. All rights reserved.OBJECTIVE: The aim of this study is to evaluate the association between Nutritional Risk Index (NRI), a simple tool to assess nutritional status, and coronary artery disease severity and complexity in patients undergoing coronary angiography. METHODS: This study is a retrospective analysis of 822 patients undergoing coronary angiography. Patients with previous revascularization were excluded. Gensini and SYNTAX scores were calculated according to the angiographic images to determine atherosclerosis severity. NRI was calculated as follows: NRI = [15.19 × serum albumin (g/dl)] + [41.7 × (body weight/ideal body weight)]. In patients ≥65 years of age, Geriatric NRI (GNRI) was used instead of NRI. GNRI was calculated as follows: GNRI = [14.89 × serum albumin (g/dl)] + [41.7 × (body weight/ideal body weight)]. Patients were then divided into three groups as previously reported: NRI < 92, NRI 92-98 and NRI > 98. Gensini and SYNTAX scores were compared between three groups. RESULTS: The mean age of study population was 61.9 ± 11.1 years. NRI < 92, 92-98, and >98 was measured in 212, 321 and 289 patients, respectively. There was no difference regarding to sex, BMI, smoking, hypertension and diabetes mellitus between three groups. Patients with NRI < 92 had the highest mean Gensini score than the patients with NRI 92-98 and NRI > 98 (38.0 ± 40.6 vs. 31.17 ± 42.4 vs. 25.8 ± 38.4, P = 0.005). Also patients with NRI < 92 had the highest mean SYNTAX score than the patients with NRI 92-98 and NRI > 98 (11.8 ± 12.9 vs. 9.3 ± 12.4 vs. 7.7 ± 11.8, P = 0.001). Also, Gensini score of ≥20 and high SYNTAX score of ≥33 were associated with lower NRI (P < 0.001 and P < 0.001, respectively). CONCLUSION: In our study, nutritional status evaluated by the NRI was associated with more extensive and complex coronary atherosclerosis in patients undergoing coronary angiography.