Longitudinal Changes of BMI and Renal Function Biomarkers During the Final 3 Years of Life Among Hospitalized Patients with Schizophrenia in Japan: A Preliminary Study

Patients with schizophrenia face high mortality from physical comorbidities; nonetheless, the gradual physiological decline preceding death is not well characterized. This retrospective study investigated temporal changes in key biomarkers among 64 inpatients with schizophrenia who died between 2014 and 2022. We analyzed data on body mass index (BMI), serum albumin (ALB), blood urea nitrogen/creatinine ratio (BCR), blood urea nitrogen/ALB ratio (BAR), and estimated glomerular filtration rate (eGFR) collected at five time points: 3, 2, and 1 year, 6 months before death, and prior to death. We hypothesized that these markers would exhibit significant changes during the last 3 years of life. BMI and ALB significantly decreased, while BCR and BAR increased (all p < 0.001). This pattern was also noted in the pneumonia subgroup, the leading cause of death (47%). A high BCR concomitant with low eGFR was attributable to chronic kidney failure in only 6% of patients, suggesting the elevated ratio was mostly driven by non-renal factors such as dehydration or sarcopenia. Therefore, the concurrent decline in BMI and ALB and rise in BCR and BAR represent a pattern of terminal physiological decline among patients with schizophrenia, supporting the need for timely risk assessment.