Trends in Depression Among Hospitalized Patients with Type 2 Diabetes in Spain (2017–2023): A Population-Based Analysis with a Focus on Sex Differences and In-Hospital Outcomes

Background/Objectives: There is a growing body of evidence supporting a bidirectional relationship between depression and type 2 diabetes mellitus (T2DM). The coexistence of depression and T2DM has substantial clinical implications. However, there is little research looking at how these two conditions cluster together in people hospitalized with T2DM, the associated factors, and their effect on hospital outcomes. In this study, we aimed to assess temporal trends in depression prevalence among hospitalized patients with T2DM in Spain from 2017 to 2023. Additionally, we analyzed the association of variables such as gender, age, anxiety, obesity, alcohol and tobacco use, dementia, COVID-19 infection, and personality disorders in the presence of depression among hospitalized T2DM patients and the impact of these variables on in-hospital mortality (IHM). Methods: We conducted a population-based cohort study using the Spanish Hospital Discharge Registry (RAE-CMBD). Adults aged ≥ 40 years with a T2DM diagnosis were included. Depression was identified by using ICD-10 codes. Time trends were analyzed by using joinpoint regression. Multivariable logistic regression models were employed to identify factors associated with depression and in-hospital mortality (IHM), stratified by sex. Results: Among 4,597,668 hospitalizations with T2DM, 202,094 (4.39%) included a depression diagnosis. Depression prevalence increased slightly over time (APC: 1.09% in women and 0.98% in men). Women consistently showed higher prevalence (OR 3.21; 95% CI: 3.18–3.24). Age, anxiety, obesity, alcohol and tobacco use, and personality disorders were significantly associated with the presence of a code for depression, with notable sex differences. Among patients with T2DM and depression, IHM was significantly associated with older age, more comorbidities, COVID-19 infection, hypoglycemia, dementia, and female gender, whereas obesity and anxiety had a protective effect. Conclusions: From 2017 to 2023, the prevalence of depression in hospitalized patients with T2DM in Spain increased slightly, particularly among older women, highlighting the need for integrated mental health screening and management during hospitalization.