Associations Between Body Mass Index Trajectories and Healthcare Utilization and Costs Among Patients with Type 2 Diabetes in Finland.

PURPOSE: We assessed how body mass index (BMI) trajectories were associated with healthcare utilization and costs in patients with type 2 diabetes (T2D). PATIENTS AND METHODS: In this retrospective cohort study, electronic health records from all public healthcare in North Karelia, Finland, were used. Patients newly diagnosed with T2D in 2011-2014 were included. The 10-year BMI trajectories since T2D diagnosis were estimated by growth mixture modeling. Time trends of healthcare utilization and costs from 2012 to 2024, and accumulated healthcare utilization over time within and between BMI trajectories were analyzed using age- and sex-adjusted regression models. Group differences in accumulated healthcare costs with 95% confidence intervals (Cls) were estimated using nonparametric bootstrapping. RESULTS: Among 3539 patients, 2750 (77.7%) were classified as having stable, 517 (14.6%) increasing, and 272 (7.7%) decreasing BMI trajectories. From 2012 to 2024, mean annual number of specific healthcare utilization and costs increased within BMI trajectories. Compared with the stable BMI trajectory, increasing BMI was associated with 9-55% higher healthcare unitization rates, particularly for all-cause, T2D-related, microvascular, mental health, and inpatient outcomes, over a mean follow-up of 10.8 years (rate ratios ranging from 1.09 to 1.55; 95% CI 1.01-1.86). A similar pattern was observed for accumulated healthcare costs, with mean differences (95% CI) of 6065 € (2741-9795 €) for all causes, 559 € (86 -1174 €) for T2D, 136 € (18-246 €) for microvascular complications, and 312 € (140-509 €) for mental health, and 6477 € (1213-11,889 €) for inpatient stays. However, decreasing BMI was associated with higher accumulated healthcare utilization and costs for macrovascular, mental health, and inpatient outcomes. CONCLUSION: Our findings emphasize the importance of monitoring and managing BMI in patients with T2D. However, the observed associations with the decreasing BMI trajectory should be interpreted with caution, as declining BMI may reflect unintentional weight loss.