Identifying distinct clusters of ICU survivors by integrating demographic, pre-admission quality of life, and clinical data: a large prospective cohort study

Purpose: ICU patients differ in pre-ICU health status, comorbidities, and diagnosis, forming a heterogeneous population with diverse long-term outcomes. This study explored whether clustering ICU patients by demographic, pre-admission quality of life, and clinical data, rather than by diagnosis, could identify subgroups that are more informative for patient-centered outcomes post-ICU. Methods: Data from the MONITOR-IC prospective cohort study were used. Demographic, pre-admission quality of life, and clinical data from 2361 adult ICU survivors of six hospitals were used to identify clusters, using the k-prototypes algorithm. Data from five additional hospitals (n = 866) were used for external validation. Self-reported physical, mental, and cognitive functioning, and quality of life one year post-ICU were described. Results: The four identified clusters differed significantly in long-term physical, mental, and cognitive functioning, and quality of life. Cluster-A (n = 204), characterized by a healthy pre-ICU status, high disease severity, low Glasgow Coma Scale, and long ICU stay, had a relatively high quality of life at one year, despite experiencing a mean decline from baseline. Cluster-B (n = 877), also a healthy group before admission but less severely ill at ICU admission, reported the best outcomes. Cluster-C (n = 632) included younger, mostly female patients with moderate impairments both pre- and one-year post-ICU. Cluster-D (n = 648), characterized by a low education level and poor baseline health, reported impaired outcomes one year post-ICU, although improved compared to their pre-admission status. External validation confirmed the generalizability of these results. Conclusion: This study identified and externally validated four distinct clusters of ICU patients by integrating both clinical and non-clinical data. These clusters, which differed in long-term physical, mental, and cognitive outcomes, challenge conventional disease-based classification, and support a multidimensional approach to define subgroups of ICU patients. Trial registration: The MONITOR-IC study was registered at ClinicalTrials.gov: NCT03246334.