Background: Type 2 diabetes mellitus (T2DM) is a prevalent chronic disease often accompanied by low-grade inflammation. Recently, the neutrophil-to-lymphocyte ratio (NLR) has garnered researchers' interest as an emerging inflammation biomarker. This study aimed to comprehensively explore the relationship between NLR and T2DM using the National Health and Nutrition Examination Survey (NHANES) database.

Method: We employed a cross-sectional study design to analyze data from five NHANES cycles from 2007 to 2016, excluding individuals with incomplete data. This study utilized a weighted logistic regression model, subgroup analyses, and restricted cubic spline (RCS) analysis to assess the potential relationship between NLR and T2DM.

Results: A total of 9903 participants were eligible for the analysis, of which 1280 were diagnosed with T2DM. The T2DM group exhibited significantly higher NLR levels than the non-T2DM group. After adjusting for potential confounders, elevated NLR levels were associated with an increased risk of developing T2DM, indicated by an odds ratio (OR) of 1.14, 95% CI: (1.05,1.24), P = 0.003. The results of the subgroup analyses revealed a significant interaction effect between NLR and T2DM concerning race and hypertension (P for interaction < 0.05). In contrast, no significant interactions were found for age, sex, education level, body mass index (BMI), smoking status, recreational activities, and alcohol drinker (P for interaction > 0.05). RCS analysis showed a significant non-linear relationship between NLR and T2DM, with an inflection point at 2.27 (all P for non-linearity < 0.05).

Conclusion: Our study indicates that an elevated neutrophil-to-lymphocyte ratio is associated with a higher risk of T2DM.