[Heterogeneous population characteristics of short-term changes in severe osteoporosis]

To explore heterogeneous population characteristics of short-term symptom scores and bone mineral (BMD) density changes in patients with severe osteoporosis (OP), in order to provide a basis for early identification of patient differences and design of subsequent research based on real-world clinical data.

Observational data of 257 patients with severe OP who met inclusion criteria from March 2020 to October 2021 were included. At the 3-month follow-up point, the symptom score changes and BMD changes were used to define "significant change" and "non-significant change" classification labels respectively. XGBoost(eXtreme Gradient Boosting) algorithm was employed to construct a change classification model. Combined with SHAP(Shapley Additive exPlanations) interpretation algorithm and rule extraction technology, feature analysis was conducted on the two types of short-term change heterogeneous populations.

Based on the change classification model, a total of 17 decision rules were extracted. The rules for changes in short-term symptom scores and BMD were mainly composed of compound conditions, clearly presented the characteristics of "significant change" group under the interaction of multiple baseline factors. ① Rules for symptom score changes. The composite interaction characteristics of the combined features of blood pressure parameters (systolic blood pressure≤124.5 to 149.5 mmHg, diastolic blood pressure>78 mmHg) with the symptom items such as "weakness in waist and knees" ≤ 3.5 points, "difficulty in bearing weight"≤3.5 points, "leg cramps">2.5 points, and "back pain">3.5 points were highlighted. These characteristics were also influenced by factors such as age, body mass index (BMI), and baseline BMD. ② Rules for BMD changes. The core of this rule was the interaction window between age (55.5 to 63.5 years old) and specific intervals of baseline BMD T/Z values (T value≤-2.85 or -3.15126.5 mmHg and diastolic blood pressure was≤69.5 mmHg. Both types of rules involved the interaction of multiple factors such as age, disease duration, and baseline BMD levels.

The short-term variability in severe OP patients has identifiable composite characteristics. The changes in symptom scores serve as an effective indicator reflecting the overall recovery status of body and functions of muscles and bones in the early stage. Although the changes in BMD are relatively less, when combined with age, bone mass baseline, and blood pressure patterns, they could provide early clues for individualized monitoring and intervention adjustments. These characteristics make up for the early differences which are easily overlooked in long-term evaluations, providing a highly differentiated and refined reference for clinical decision-making.