Objective To investigate the influencing factors of secondary type 2 diabetes in young obesity patients, and construct and validate a risk prediction model.

Methods The retrospective cohort study was conducted. The clinical data of 847 young obesity patients who were admitted to The First Affiliated Hospital of Nanjing Medical University from January 2022 to July 2024 were collected. There were 382 males and 465 females, aged (29.4±3.8)years. Patients were randomly divided into a training set of 593 cases and a validation set of 254 cases based on a random number table method of 7∶3 ratio. The training set was used to construct the prediction model, and the validation set was used to validate prediction model. Observation indicators: (1) analysis of influencing factors of secondary type 2 diabetes in young obesity patients; (2) construc-tion and validation of a prediction model for secondary type 2 diabetes in young obesity patients. Comparison of measurement data with normal distribution between groups was conducted using the independent sample t test. Comparison of measurement data with skewed distribution between groups was conducted using the Mann‑Whitney U test. Comparison of count data between groups was conducted using the chi‑square test. Univariate analysis was performed using the corresponding statistical methods based on data types. Multivariate analysis was performed using the Logistic regression model, and the area under the curve (AUC) of receiver operating characteristic (ROC) curve, the Hosmer‑Lemeshow test, the calibration curve and decision curve were used to evaluate the predictive performance of the model.

Results (1) Analysis of influencing factors of secondary type 2 diabetes in young obesity patients. Of the 847 young obesity patients, there were 238 patients with secondary type 2 diabetes, including 161 cases in the training set and 77 cases in the validation set, 609 patients of simple obesity, including 432 cases in the training set and 177 cases in the validation set. Results of multivariate analysis showed that family history of diabetes, hypertension, high‑sugar diet, exercise habits, triglyceride (TG), homeostasis model assessment of insulin resistance (HOMA‑IR) and neutrophil‑to‑lymphocyte ratio (NLR) were independent factors influencing secondary type 2 diabetes in young obesity patients odds ratio=9.476, 2.420, 3.219, 0.272, 2.137, 26.759, 41.535, 95% confidence interval (CI) as 3.242-27.696, 1.159-5.052, 1.525-6.796, 0.117-0.632, 1.019-4.481, 12.907-55.476, 16.085-107.251, P<0.05. (2) Construction and validation of a prediction model for secondary type 2 diabetes in young obesity patients. A nomogram prediction model for secondary type 2 diabetes in young obesity patients was constructed based on the results of multivariate analysis. Results of ROC curve analysis showed that the AUC of prediction model for the training set was 0.963(95%CI as 0.946-0.980), with sensitivity of 89.6% and specificity of 93.2%, respectively, and the AUC of prediction model for the validation set was 0.966(95%CI as 0.944-0.988), with sensitivity of 92.7% and specificity of 88.3%, respectively. Results of Hosmer‑Lemeshow test showed that the P‑values for both the training set and validation set were >0.05, indicating good model fit. The calibration curves for both the training set and validation set closely matched the actual curve, demonstrating the prediction model with a good fit. The decision curve analysis showed high practical value of the model.

Conclusions Family history of diabetes, hypertension, high‑sugar diet, exercise habits, TG, HOMA‑IR and NLR are independent factors influencing secondary type 2 diabetes in young obesity patients. The prediction model constructed based on these factors demons-trates good predictive performance.