Gut microbiome in the elderly hospitalized patient: a marker of disease and prognosis?

In community-dwelling older people, gut microbiota is generally characterized by reduced species richness, increased interindividual variability, and reduced resilience after a stressful event. These features are more pronounced in centenarians and persons with mobility limitations. Hospitalization for acute illness represents one of the most challenging stressors for the gut microbiota, which rapidly changes toward dysbiosis and increased representation of pathobionts. These phenomena are particularly emphasized in older people and in subjects admitted to intensive care units. The hospitalization-associated gut microbiota alterations may also be associated with adverse clinical outcomes, such as mortality, infection, disability, and risk of readmission. These issues have been only marginally studied to date, and the clinical transition of microbiome analyses in older hospitalized patients is often difficult to understand. The gut microbiota composition may however represent a promising marker of prognostic trajectories of older patients.