Objective To analyze the predictive value of 15-item geriatric depression scale (GDS-15)-simplified version, morse falls assessment scale (MFS), Pittsburgh sleep quality index (PSQI) and hemoglobin A1c (HbA1c) on cognitive decline in elderly patients with type 2 diabetes mellitus (T2DM) complicated with hypertension, and to construct a risk-line chart prediction model. Methods A total of 88 elderly patients with T2DM complicated with hypertension who attended Luohe Municipal Hospital from August 2024 to August 2025 were retrospectively selected. Based on the occurrence of cognitive impairment, they were divided into an impairment group and a non-impairment group. Data collected for both groups included GDS-15 scores, MFS scores, and PSQI scores, and HbA1c levels. Variables showing significant differences were incorporated into a Logistic regression model to investigate factors associated with cognitive impairment in elderly patients with T2DM and hypertension. A risk prediction model was constructed to evaluate predictive performance. Results Among 88 elderly patients with T2DM complicated with hypertension, 26 experienced cognitive impairment, while 62 did not. The MFS score and PSQI score of the occurrence group were higher than those of the non occurrence group (both P＜ 0.05), while the GDS-15 score and HbA1c level were lower than those of the non occurrence group (both P＜0.05). The results of logistic regression analysis showed that high MFS score and high PSQI score were both risk factors for cognitive impairment in elderly patients with T2DM complicated with hypertension (both P＜0.05), low GDS-15 score and low HbA1c level were both protective factors (both P＜0.05). The area under the curve (AUC) value of the risk prediction model for the line chart was 0.994, indicated high predictive value. Conclusion GDS-15 score, MFS score, PSQI score, and HbA1c levels demonstrate predictive value for cognitive decline in elderly patients with T2DM complicated with hypertension. These factors enable timely identification of high-risk individuals and the development of corresponding intervention strategies.