Oral microbiome linked to postoperative delirium after head and neck cancer surgery

Patients with oral squamous cell carcinoma who developed delirium after surgery showed a different preoperative oral microbiome than those who did not, according to an exploratory study published in Translational Psychiatry. The researchers analysed preoperative oral rinse samples from 181 patients undergoing major head and neck cancer surgery, of whom 27 developed postoperative delirium, using 16S rRNA gene sequencing to characterise bacterial communities.

Patients who developed delirium had lower microbial richness, measured by the Observed and Chao1 indices, indicating fewer distinct bacterial types in their mouths before surgery. Overall community composition also differed significantly between the groups, as shown by Canberra and unweighted UniFrac distance measures, which compare both the abundance and evolutionary relatedness of microbial species.

Differential abundance analysis identified two genera associated with delirium before statistical adjustment for clinical factors, and 15 genera after adjustment. Among the adjusted findings, the delirium group showed higher abundances of Haemophilus and Neisseria. Functional prediction of the microbial genomes suggested higher activity in glycerophospholipid and nitrogen metabolism pathways in the delirium group, and analyses stratified by intensive care unit length of stay revealed additional pathway differences between the groups.

The authors emphasise that this is an exploratory study: the results are preliminary and require validation in independent cohorts and longitudinal studies before any conclusions can be drawn about cause and effect. The findings indicate an association between preoperative oral microbiome composition and postoperative delirium in this patient population, but they do not establish that the microbiome causes delirium.

Postoperative delirium is a common complication after major head and neck cancer surgery, and its relationship with the preoperative oral microbiome had remained unclear. By profiling oral bacteria before surgery and adjusting for relevant clinical factors, the study provides a first map of which microbial features distinguish patients who later develop delirium, offering a basis for future confirmatory research.

Subject of Research: The association between preoperative oral microbiome profiles and postoperative delirium in patients with oral squamous cell carcinoma

Article Title: Exploring the relationship between oral microbiome and postoperative delirium in patients with oral squamous cell carcinoma

Article References: Hung, S. Y., Chang, K.-P., Chu, C.-L., Chen, Y.-L., Lin, S.-H., Lee, C.-Y., Yang, C. Y., & Fu, S.-C. (2026). Exploring the relationship between oral microbiome and postoperative delirium in patients with oral squamous cell carcinoma. Translational Psychiatry. https://doi.org/10.1038/s41398-026-04489-2

Image Credits: AI Generated

DOI: 10.1038/s41398-026-04489-2

Keywords: oral microbiome, postoperative delirium, oral squamous cell carcinoma, 16S rRNA sequencing, head and neck surgery, microbial diversity, Haemophilus, Neisseria, Translational Psychiatry, exploratory study, Exploring, relationship