Objective:To investigate the correlation between neutrophil to lymphocyte ratio (NLR), D-dimer, residual lipoprotein cholesterol (RLP-C) levels and the occurrence and severity of acute myocardial infarction in young adults.Methods:A total of 96 young patients with acute myocardial infarction who visited the First People′s Hospital of Kashgar from June 2020 to June 2022 were retrospectively selected as the observation group, and 100 healthy volunteers who underwent physical examinations at our hospital during the same period were selected as the control group. The serum NLR, D-dimer, and RLP-C levels of the two groups of patients were compared. Coronary angiography was performed on the patients, and the observation group patients were divided into mild stenosis, moderate stenosis, and severe stenosis subgroups based on their Gensini scores. The serum NLR, D-dimer, and RLP-C levels of patients in different subgroups were recorded and compared. Pearson correlation analysis was used to determine the correlation between serum NLR, D-dimer, and RLP-C levels and patients′ Gensini scores. The diagnostic value of NLR, D-dimer, and RLP-C levels in young patients with acute myocardial infarction and severe coronary artery stenosis was explored using receiver operating characteristic (ROC) curves.Results:The levels of NLR, D-dimer, and RLP-C in the observation group were significantly higher than those in the control group (all P<0.05). The ROC curve analysis results showed that the area under the curve (AUC) for diagnosing acute myocardial infarction in young patients with NLR, D-dimer, and RLP-C were 0.942, 0.865, and 0.970, respectively (all P<0.05). The levels of NLR, D-dimer, and RLP-C in patients with severe stenosis were higher than those in patients with mild to moderate stenosis (all P<0.05). Pearson correlation analysis showed that the levels of NLR, D-dimer, RLP-C in young patients with acute myocardial infarction were positively correlated with Gensini score ( r=0.806, 0.843, 0.851, all P<0.001). The ROC curve analysis results showed that the AUC values of NLR, D-dimer, and RLP-C levels for diagnosing severe coronary artery stenosis in young patients with acute myocardial infarction were 0.915, 0.874, and 0.922, respectively (all P<0.05). Conclusions:The levels of NLR, D-dimer, and RLP-C are elevated in young patients with acute myocardial infarction, and are positively correlated with the severity of the disease. Clinical attention should be closely monitored.