Journal of Health Wellness and Community Research · Jan 30, 2026
Gut Microbiome Signatures Predict ICU Delirium Risk in Mechanically Ventilated Older Adults
By Zubair A, Mahmood MS, Ashraf A et al.
Background: ICU delirium is a frequent neurological complication of critical illness, while emerging evidence suggests that intestinal dysbiosis may contribute to neurological vulnerability through microbiota-gut-brain interactions. Objective: To investigate the relationship between early gut microbiome characteristics and ICU delirium in mechanically ventilated adults aged ≥65 years. Methods: This analytical observational study included 85 mechanically ventilated older adults treated in tertiary-care ICUs in Punjab between September and December 2025. Fecal samples obtained within 48 hours of mechanical ventilation were analysed using 16S rRNA gene sequencing. Delirium was assessed twice daily using CAM-ICU. Microbial diversity and selected bacterial families were compared according to delirium status, followed by multivariable logistic regression adjusting for age, APACHE II score, and broad-spectrum antibiotic exposure. Results: Delirium occurred in 38/85 participants (44.7%). Shannon diversity was lower in participants with delirium than without delirium (2.14±0.45 vs 3.12±0.58; mean difference −0.98, 95% CI −1.20 to −0.76; p<0.001). Lachnospiraceae (4.2% vs 12.8%) and Ruminococcaceae (3.6% vs 9.4%) were depleted, whereas Enterococcaceae was increased (8.9% vs 2.4%). Higher Shannon diversity (aOR 0.35, 95% CI 0.18–0.68; p=0.003) and greater Lachnospiraceae abundance (aOR 0.78, 95% CI 0.64–0.94; p=0.011) were independently associated with lower odds of delirium. Conclusion: ICU delirium was associated with reduced microbial diversity and altered bacterial composition. These findings support further prospective validation of gut microbiome characteristics as potential markers of delirium vulnerability